30 de novembro de 2022

Aboriginal diets

In August 1984, I discussed aboriginal diets with the late Sylvia Hallam (https://en.wikipedia.org/wiki/Sylvia_Hallam) and the late Hilary Deacon (https://en.wikipedia.org/wiki/Hilary_Deacon).

The aboriginal population of Australia was remarkably sparse: possibly less than 0.5 million on the whole continent.

Dioscorea hastifolia (https://www.inaturalist.org/taxa/1003647-Dioscorea-hastifolia) is an indigenous liane

occurs in a habitat-duality which I have found repeatedly: granite outcrops and alluvial banks.

In the relatively nutrient-poor landscapes of southern Australia and southern Africa, both situations are somewhat enriched, the first by fresh weathering, and the second by concentration via the flow of water.

On alluvial banks, D. hastifolia grew in 'thickets' of Jacksonia sternbergiana (https://florabase.dpaw.wa.gov.au/browse/profile/4029 and https://www.inaturalist.org/taxa/525347-Jacksonia-sternbergiana), a nitrogen-fixing tall shrub or low tree. The liane also climbed on the cycad Macrozamia riedlei (https://www.inaturalist.org/taxa/135854-Macrozamia-riedlei), also a nitrogen-fixer.

In southwestern Western Australia, D. hastifolia occurred in local 'colonies', which were maintained free of the fires otherwise ubiquitous in the area. Here, there were permanent 'rabbit-warren' holes dug by aboriginal people, to a depth of several metres in places. This repeated and intensive harvesting was tantamount to a kind of culturing of the food-plant. Some patches of Dioscorea were fairly extensive, viz. several hundred metres in diameter.

Examples occurred at Upper Swan (https://en.wikipedia.org/wiki/Upper_Swan,_Western_Australia), where D. hastifolia formed fire-protected foci within forest of Eucalyptus rudis (https://en.wikipedia.org/wiki/Eucalyptus_rudis), which was regularly burned by the aboriginal people.

Alluvial substrates were particularly supportive of the aboriginal people, because of the incidence of Typha domingensis (https://www.inaturalist.org/taxa/58392-Typha-domingensis) and Typha orientalis (https://www.inaturalist.org/taxa/341639-Typha-orientalis), with their edible rhizomes.

The tubers of D. hastifolia were of diameter 1.3-4 cm and length up to 60 cm. This large size meant that tbeybwere economkcal to excavate, compared to the other tubers in this flora, all of which are small.

The aboriginal people also mate the bulbs of Haemodorum (https://www.inaturalist.org/observations?place_id=6827&taxon_id=700230&view=species), an element of the kwongan flora, associated with extremely njteient-poor sandplains.

In the southwestern Cape of South Africa, the aboriginal people depended mainly on geophytes. However, these did not include any species of Dioscorea.

Here, Watsonia (https://www.inaturalist.org/observations?place_id=any&taxon_id=72425&view=species) was the main food, in places. This corm is starchy, containing less protein than e.g. domestic potato (Solanum tuberosum).

This - the rapid spread of Watsonia as an invasive weed in southwestern Australia notwithstanding - was a slowly-renewing resource, the harvested corms taking up to 4-5 years to be replaced.

Publicado em 30 de novembro de 2022, 06:03 AM por milewski milewski | 0 comentários | Deixar um comentário

29 de novembro de 2022

Geophytic flora of Wongan Hills Nature Reserve, southwestern Western Australia

https://exploreparks.dbca.wa.gov.au/park/wongan-hills-nature-reserve and https://www.wongan.wa.gov.au/discover/arts-heritage-and-culture/tourism.aspx

Kenneally 1977 https://bookmerchant.com.au/products/The-Natural-History-of-the-Wongan-Hills-coordinated-by-Kevin-Kenneally-p491120089

Mediterranean-type climate
Mean annual rainfall 390 mm


Total vascular flora 409 spp.

Geophytic flora 33 spp. (= 8% of flora, consisting mainly of orchids)

Pauridia occidentalis damp areas of gulley

Caesia parviflora damp areas
https://www.inaturalist.org/taxa/323895-Caesia-parviflora and https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Caesia~parviflora

Chamaescilla corymbosa damp red soil

Thysanotus patersonii widespread
Thysanotus sp. rare, hill slope
Wurmbea tenella damp ground

Orchidaceae: all occur on lateritic substrates, in kwongan vegetation, as well as alluvial soils in the gulley, and in woodland of Eucalyptus salmonophloia
Caladenia 8 spp.
Diuris 1 sp.
Eriochilus 1 sp.
Lyperanthus 1 sp.
Pterostylis 6 spp.
Thelymitra 1 sp.

Stylidium caricifolium laterite

Platysace cirrosa red soil of apron of breakaway
Platysace maxwellii kwongan

Drosera aff bulbosa greenstone scree
Drosera macrantha laterite
Drosera macrophylla damp red soil
Drosera menziesii kwongan
Drosera aff stolonifera kwongan
Drosera zonaria kwongan


Caesia is a genus shared among Australia, Madagascar, and the Cape Floristic Region of South Africa. It is root-tuberous. However, the development of the tubers is minimal in C. parviflora.

Publicado em 29 de novembro de 2022, 10:43 AM por milewski milewski | 2 comentários | Deixar um comentário

27 de novembro de 2022

Communities of geophytes in Fitzgerald River National Park, Western Australia, by vegetation type

(writing in progress)

The southwestern region of Western Australia has a mediterranean-type climate, flat topography, generally nutrient-poor soils, and a natural regime of intense wildfires.

Geophytes (https://en.wikipedia.org/wiki/Storage_organ) in this region consist mainly of orchids with small root-tubers. However, the incidence of stem-tuberous droseras is significant.

An odd category of geophytes has evolved within the speciose genus Stylidium (https://www.publish.csiro.au/SB/SB12001).

In southwestern Western Australia, the monocotyledonous geophytic flora contributes 7% of the total flora. This is only half the value for the Cape Flora of South Africa, which is environmentally similar (https://www.publish.csiro.au/BT/BT02067 and https://www.researchgate.net/publication/248899409_Monocotyledonous_geophytes_comparison_of_south-western_Australia_with_other_areas_of_Mediterranean_climate).

If comparison is made with California, another region of mediterranean-type climate, the main difference is in bulbous plants - which differ greatly in incidence and type in the two regions.

Unlike all other regions of mediterranean-type climate on Earth, Australia lacks any form of fossorial/ subterranean, geophyte-eating rodent (mole-rat or gopher).

In this Post, I summarise the incidence of the various types of geophytes in the main vegetation types in Fitzgerald River National Park (FRNP).

Coastal forest (moort) of EUCALYPTUS PLATYPUS and Melaleuca lanceolata (moonah), on deep calcareous sand

Incidence of geophytes variable (nil in Melaleuca lanceolata over moss-crusted, undisturbed calcareous sand, so perhaps split off Melaleuca lanceolata into another category)
Incidence of geophytes very similar to inland E. platypus, despite the different substrate
Community of geophytes poorer than in woodland of Eucalyptus occidentalis
up to 6 spp. of orchids (only where E. platypus)
Thysanotus patersonii (only where E. platypus)

Low forest (moort/marlock) of EUCALYPTUS conferruminata/lehmannii/macrandra etc. on various substrates
sampled by 11 plots
Clear result, but unknown after wildfire
a few (up to 5) spp. of orchids
Thysanotus patersonii https://www.inaturalist.org/taxa/323937-Thysanotus-patersonii
sometimes no geophytes detected in a given stand, even in spring
no droseras
no geophytic stylidiums
no stem-tubers of any kind

Low forest/woodland (sheoak) of ALLOCASUARINA
Note landform duality, which reflects role of nutrients, P, K
Richest in geophytes where combination of alluvium and fresh weathering?
Similar to the richer communities in woodland of E. occidentalis
Thysanotus patersonii (and T. aff pyg)
Orchids variable, up to 11 spp.
Stylidium crassifolium (https://www.inaturalist.org/taxa/145683-Stylidium-crassifolium) and Stylidium dichotomum (https://www.inaturalist.org/taxa/145686-Stylidium-dichotomum)
Drosera spp. (?not as uncommon as in woodland of E. occidentalis)
Chamaescilla corymbosa and Chamaescilla spiralis
Hypoxis lept (https://www.inaturalist.org/observations?place_id=6827&taxon_id=71542&view=species) (is this Pauridia glabella?)
Wurmbea tenella (https://www.inaturalist.org/taxa/925387-Wurmbea-tenella)
Glycine clandestina/rubiginosa (geophyte?)(https://www.inaturalist.org/taxa/321122-Glycine-clandestina and https://www.inaturalist.org/taxa/555940-Glycine-rubiginosa)
Ptilotus spathulatus (https://www.inaturalist.org/taxa/202124-Ptilotus-spathulatus)
Caesia parviflora uncommon (https://www.inaturalist.org/taxa/323895-Caesia-parviflora)
Utricularia violacea (geophyte?)(https://www.inaturalist.org/taxa/1043839-Utricularia-violacea)
Craspedia (https://www.inaturalist.org/observations?place_id=6827&taxon_id=323539&view=species)

Mallee of EUCALYPTUS spp.
Similar to marlock, but additional geophytes present
as in marlock, a few spp. of orchids, and Thysanotus patersonii
In some plots, a stylidium is the only geophyte present
Orchids (0-4 spp. per plot) usually including Pterostylis
Drosera does occur here, including geophyte? (macrophylla, https://www.inaturalist.org/taxa/924850-Drosera-macrophylla)
Stylidium e.g. albomontis (https://www.inaturalist.org/taxa/145667-Stylidium-albomontis) occurs as geophyte, different from marlock
Ptilotus drummondii (https://www.inaturalist.org/taxa/511202-Ptilotus-drummondii) and Ptilotus holosericeus (https://www.inaturalist.org/taxa/972186-Ptilotus-holosericeus), different from marlock
In one plot on well-drained deep soil, Wahlenbergia multicaulis (https://www.inaturalist.org/taxa/520378-Wahlenbergia-multicaulis)(which other landform was this geophyte found on?)

Mallee-heath of EUCALYPTUS spp. over a diverse lower stratum, in duplex substrates (sand over clay)
most geophytes on well-drained duplex over granite
poor in orchids, as in scrub-heath
in general, as many or more Drosera spp. than orchid spp. per site (true for geophytes?)
more lilies and Haemodorum than in scrub-heath (as statedii by Brown and Hopkins)
never more than 2 spp. of orchids per plot
Stylidium piliferum and Sytilidium schoenoides (https://www.inaturalist.org/taxa/145502-Stylidium-schoenoides) and Stylidium albomontis
Drosera a few spp. including D. menziesii
Anigozanthos humilis (https://www.inaturalist.org/taxa/123210-Anigozanthos-humilis)
Haemodorum paniculatum (also in wandoo, but not found in scrub-heath)
Chamaescilla spiralis (https://www.inaturalist.org/taxa/912133-Chamaescilla-spiralis)(also in wandoo, but not found in scrub-heath)
Why no Thysanotus, not even patersonii?
Compared with mallee: shares Stylidium, orchids, and Drosera, but differs in that Thysanotus patersonii of mallee is absent, and the ptilotus (and wahlenbergia) of mallee are replaced in mallee-heath by sparse Chamaescilla and Haemodorum (sand elements)

Woodland (yate) of EUCALYPTUS OCCIDENTALIS on loam
Machaerina occurs where wet in winter
The incidence of geophytes on alluvium under yate is very variable, partly owing to variation in drainage. Geophytes are rare on winter-inundated (which is surprising)(and saline) sites
Overall, richer (in stem tubers?) than mallee, especially in terms of taxonomic diversity (families)
Radical difference according to drainage, but some well-drained plots also poor, for unknown reasons
Stylidium geophytes strangely absent, but other stem-tuberous geophytes present
ANNUALS (cf mallee and moort)
geophytic droseras rare (just D. menziesii https://www.inaturalist.org/taxa/148225-Drosera-menziesii in one plot)
Where well-drained, orchids 0-17 (large variation)
Thysanotus patersonii (and T. aff pyramidalis https://www.inaturalist.org/taxa/862789-Thysanotus-pyramidalis, in one plot)
Wurmbea tenella (https://www.inaturalist.org/taxa/925387-Wurmbea-tenella) uncommon
Chamaescilla corymbosa (https://www.inaturalist.org/taxa/194766-Chamaescilla-corymbosa) uncommon
Hyp glabella uncommon
Lagenophora huegelii
Convolvulus erubescens (https://www.inaturalist.org/taxa/210190-Convolvulus-erubescens)
Glycine clandestina (geophyte?)(https://www.inaturalist.org/taxa/321122-Glycine-clandestina)
Ptilotus spathulatus (https://www.inaturalist.org/taxa/202124-Ptilotus-spathulatus)
Gonocarpus dura
Marsilea drummondii (geophyte?)(https://www.inaturalist.org/taxa/738930-Marsilea-drummondii)

Note: no Wurmbea, Ptilotus spathulatus, Craspedia, or Caesia
Stylidium, Drosera, and orchids are usually present, with similar numbers of spp. per plot
orchids up to 5 spp.
Thysanotus patersonii
Stylidium spin and dichot and piliferum and albomontis and squamellosum
Drosera parvula, stolon, zon, neesii, mac, and menz
Chamaescilla spiralis and Chamaescilla corymbosa
Hypoxis lept
Haemodorum paniculatum (surprise?)
(Poly tenella)
Now cf Cas hueg

Scrub-heath of PROTEACEAE, MYRTACEAE and FABACEAE on deep siliceous sand
Poor in geophytes (0-6 spp. per plot)
All tubers small
Why no Haemodorum?
few orchids (0-4 spp. per plot)
Drosera scorpioides (geophyte?)(https://www.inaturalist.org/taxa/895673-Drosera-scorpioides)
Anigozanthos humilis (not geophyte, but explain)(also found in mallee-heath)(https://www.inaturalist.org/taxa/123210-Anigozanthos-humilis)
Thysanotus patersonii
Stylidium piliferum (https://www.inaturalist.org/taxa/567801-Stylidium-piliferum) and Stylidium albomontis (https://www.inaturalist.org/taxa/145667-Stylidium-albomontis)

Thicket of PROTEACEAE, MYRTACEAE etc. on rocky slopes of quartzite
poor in Drosera
variation in orchids poorly understood, but poverty of drosera noteworthy compared to scrub-heath and mallee-heath
Thysanotus patersonii (rare)
Drosera menziesii
Orchids 0-9 spp.
Stylidium spinulosum (https://www.inaturalist.org/taxa/1146860-Stylidium-spinulosum) and schoenoides (https://www.inaturalist.org/taxa/145502-Stylidium-schoenoides) and squamosotuberosum (https://www.inaturalist.org/taxa/855381-Stylidium-squamosotuberosum) and piliferum and albomontis
Poly tenella

Vegetation complex on exposed granite bedrock
Need more plots
Wurmbea tenella
Hypoxis lept
Pauridia glabella (https://www.inaturalist.org/taxa/748411-Pauridia-glabella and https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=in&name=Hypoxis~glabella~var.+glabella and https://keys.lucidcentral.org/keys/v3/scotia/key/Plants%20and%20Fungi%20of%20south%20western%20NSW/Media/Html/Hypoxis_glabella_var._glabella.htm)
orchids up to 22 spp.
Stylidium dichotomum (https://www.inaturalist.org/taxa/145686-Stylidium-dichotomum)
Thysanotus patersonii
Chamaescilla corymbosa
Drosera mac menz bulbosa
Pol ten
Compared to wodjil: fewer stylidium, no Haemodorum paniculatum, and more orchids in gran exp than in wodjil

Acacia scrub
Inadequate data
(writing in progress)


As in woodland of Eucalyptus occidentalis, the variation in the geophytic community in forest of Eucalyptus platypus is poorly understood. It is not simply a question of salinity.

Now take all moort and marlocks together, and split off all Mel low forest/thickets

Wurmbea (Colchicaceae) is a genus shared between Australia and southern Africa (https://www.pacificbulbsociety.org/pbswiki/index.php/wurmbea). It possesses corms (https://www.anbg.gov.au/apu/plants/wurmdioi.html).

Caesia (Asphodelaceae) is a genus shared among Australia, Madagascar, and the Cape Floristic Region of South Africa. It is root-tuberous. However, the development of the tubers is minimal in C. parviflora.

Trichocline (Asteraceae) is mainly South American, with one species occurring in Australia (https://en.wikipedia.org/wiki/Trichocline). The tubers are xylopodia (https://sweetgum.nybg.org/science/glossary/glossary-details/?irn=1703), in at least some spp.

Gardner (1949) states that, in southwestern Australia, Glycine is associated with granite rocks, as are droseras and orchids.

Publicado em 27 de novembro de 2022, 09:14 AM por milewski milewski | 16 comentários | Deixar um comentário

25 de novembro de 2022

Habitat-distinctions of plants with fleshy fruits in and near Fitzgerald River National Park, southwestern Western Australia

Various species of plants with fleshy fruits occur in/near Fitzgerald River National Park (FRNP, https://en.wikipedia.org/wiki/Fitzgerald_River_National_Park), in southwestern Australia.

The incidence of fleshy fruits, as opposed to other kinds of diaspores, may be related to the nutritional regime of the substrates in question.

In this Post, I summarise the pattern of habitat-preference by these plants. The sources are mainly those of K R Newbey (https://scholar.google.com.au/scholar?hl=en&as_sdt=0%2C5&q=Newbey+kr+fitzgerald&btnG=), together with my own observations.

Occurring patchily on calcareous substrates are

Coastal, calcareous dunes have

The following spp. are shared between calcareous sand and alluvium:

By contrast, alluvium has

Brachyloma geissoloma (https://florabase.dpaw.wa.gov.au/browse/profile/30138 and https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77175904-1) is poorly documented, but occurs, on alluvium/granite.

The only spp. potentially bearing fleshy fruits on quartzite are two spp. of Ericaceae, viz.

It is noteworthy that no species of Persoonia seems to occur on oligotrophic soils in/near FRNP.

On spongolite there are

On duplex substrates (sand over clay, presumably with mallee-heath) there are

Still to allocate: Billardiera heterophylla (https://www.inaturalist.org/taxa/75769-Billardiera-heterophylla and https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Billardiera~heterophylla)


Tetragonia implexicoma https://www.inaturalist.org/observations/141515353


The fruits of these plants (whIch, like Tetragonia, are semi-halophytic) are typically bright-hued but small. Those of Chenopodium spp. are known to be eaten by Gavicalis virescens (https://www.inaturalist.org/taxa/370319-Gavicalis-virescens), which is probably an important seed-disperser for these plants.

Atriplex semibaccata https://www.inaturalist.org/observations/141170957
Chenopodium baccatum https://www.inaturalist.org/observations/129952340
Chenopodium wilsonii https://www.inaturalist.org/observations/109633708
Enchylaena tomentosa https://www.inaturalist.org/observations/139504726
Threlkeldia diffusa https://www.inaturalist.org/observations/70989013


Alyxia buxifolia https://www.inaturalist.org/observations/126043362


Dianella revoluta https://www.inaturalist.org/observations/126035684


The fruits of these plants are all small.

Leucopogon parviflorus https://www.inaturalist.org/observations/142027641


Nitraria billardierei https://www.inaturalist.org/observations/107748929

Myoporum oppositifolium https://www.inaturalist.org/observations/16063240


These plants are all hemiparasitic.

Exocarpos aphyllus https://www.inaturalist.org/observations/135477566
Exocarpos sparteus https://www.inaturalist.org/observations/105075520
Santalum murrayanum https://www.inaturalist.org/observations/135771476


Alluvium and calcareous sand in/near FRNP, although nutrient-poor by global comparisons, are not as poor as other substrates in the area. Both have considerable floras of fleshy fruits.

The sites richest in spp. with fleshy fruits are likely to be where granitoid-derived alluvia merge with coastal dunes at inlets near the sea (e.g. Culham Inlet, see https://www.inaturalist.org/journal/milewski/62402-shrubland-ambivalent-in-its-syndromes-of-dissemination-by-animals-a-base-rich-littoral-site-at-fitzgerald-river-national-park-southwestern-australia#).

Ericaceae with fleshy fruits occur mainly on alluvia in/near FRNP. However, some may occur on granite substrates.

The following (https://tasmanianplants.wordpress.com/2009/12/25/haveya-had-ya-heaths/) gives an idea of the nature of ericaceous fleshy fruits in Tasmania. Those in/near FRNP are far more poorly developed: none has conspicuous fruits, and all are as likely to be dispersed by ants and lizards as by volant birds. The genera involved, particularly Styphelia, show a pattern in which

  • the fruits tend to be small, dull, and hidden, and
  • the spp. with the most conspicuous fruits tend to occur in the Eastern States, not Western Australia.

Also see https://www.inaturalist.org/posts/68420-unusual-combination-of-features-in-ericaceae-the-case-of-acrotriche-serrulata#.

Publicado em 25 de novembro de 2022, 10:22 PM por milewski milewski | 16 comentários | Deixar um comentário

24 de novembro de 2022

The parasitic liane Cassytha in southwestern Australia and an ecologically similar region of southern Africa

@alan_dandie @michaelcincotta @insiderelic @scottwgavins @cobaltducks @tonyrebelo @botaneek @troos @fynbosphil @fynbosfia @fynbossie @fynbosfriend @fynbosfae @graham_g @jeremygilmore @arthur_chapman @peterslingsby @benjamin_walton @jayhorn

Most spp.of the genus Cassytha (Lauraceae) occur in Australia, with two outlying spp. occurring in southern Africa.

In and near Fitzgerald River National Park (FRNP, https://breaking-the-borders.com/en/fitzgerald-river-national-park/), Western Australia, there are six spp. of Cassytha - probably the greatest diversity of perennial parasitic lianes on Earth.

Strands of various spp. of Cassytha can be found from ground level to 7 m high.

Although all have indehiscent, potentially edible fruits of common design, the size of the fruits varies considerably. Some (particularly Cassytha micrantha and Cassytha glabella) are too small to be considered fleshy fruits, and are probably dispersed and sown by ants.

This means that Cassytha is yet another of the many genera of 'plasticfruits' (https://www.inaturalist.org/journal/milewski/61996-plasticfruits-part-1-how-an-ordinary-daisy-becomes-extraordinarily-fruity#), which stretch, within a given genus, from vertebrate-dispersed to non vertebrate-dispersed spp.

Despite their diversity in/near FRNP, all forms of Cassytha are absent from calcareous sand hereabouts, except where limestone crops out, and where Eucalyptus forms dense stands.

In this region, stands of vegetation richest in lianes are the ones poorest in Cassytha, suggesting that this parasitic genus is suited to sites and strata prohibitive to other types of lianes.

The littoral dune of calcareous sand in/near FRNP, vegetated patchily by e.g. Acacia rostellifera, Melaleuca lanceolata, and Chenopodium spp., is free of Cassytha and virtually free of other parasites (whether before or after fire) despite the favourable content of phosphorus in the sand, and Cassytha was also absent from woodland of Eucalyptus occidentalis, containing Santalum on alluvium (visited in November 1991).

Cassytha melantha (https://www.inaturalist.org/taxa/733735-Cassytha-melantha)
https://www.inaturalist.org/observations/70183424 and https://www.inaturalist.org/observations/108575414 and https://www.inaturalist.org/observations/103295193 and https://www.inaturalist.org/observations/71931219
fruit dull orange-hued, diam. 0.85 cm, seed diam.0.5 cm; fruit mass >0.3 g.

Cassytha pomiformis (https://www.inaturalist.org/taxa/851596-Cassytha-pomiformis)
I observed this species in ?Banksia kwongan on deep siliceous sand (certainly SS 1 type) in/near FRNP
no photo available of fruit, which is larger than that of C. glabella
fruit oblong, hairy, fleshy, dull-hued, yellow-green-black, 1.0 X 0.6 cm

Cassytha racemosa (https://www.inaturalist.org/taxa/800963-Cassytha-racemosa)
no photo available of fruit
fruit not necessarily fleshy
fruit oval, ribbed, dull-hued, 0.7 X 0.5 cm
fruit size similar to that of C. glabella
fruit size according to literature: diam.0.4 cm (Weber 1981), 1.0 X 0.4 cm (another ref.)

Cassytha glabella (https://www.inaturalist.org/taxa/323804-Cassytha-glabella)
https://www.inaturalist.org/observations/129653032 and https://www.inaturalist.org/observations/135894298 and https://www.inaturalist.org/observations/132378556 and https://www.inaturalist.org/observations/130206723
fruit small, variable in shape, greenish or dull orange-hued, meagre-fleshy but succulent (verified by me in FRNP, Nov. 1991), 0.4 X 0.2 cm to 1.1 X 0.3 cm, seed diam. 2.5 mm. Another of my field-notes states fruit dimensions average 0.65 X 0.25 cm, but as little as 0.5 X 0.15 cm, and as much as 1.1 X 0.4 cm.

Cassytha flava (https://www.inaturalist.org/taxa/851590-Cassytha-flava)
restricted to kwongan on sandplain
no photo available of fruits
fruit small, inconspicuous, greyish, hairy, 0.5 X 0.4 cm

Cassytha micrantha (https://www.inaturalist.org/taxa/745928-Cassytha-micrantha)
no photo available of fruit
fruit extremely small, inconspicuous, 0.3 X 0.2 cm


Although all its habitats in/near FRNP are subject to fire, Cassytha shows little relationship to fires. It regenerates germinatively, in some spp. possibly from hard, long-lived seed sown before the fire (Weber 1981, Fox 1988).

Although Cassytha (pomiformis?) appears as sparse populations of semi-prostate, dark plants in the early regeneration on open, burnt ground (some stands extending 2 m across bare spaces), it is not particularly prolific at this stage (percent foliage cover <0.1% in regeneration on siliceous sand (SS1 type), two years or less after intense fire) and does not behave as a fireweed, although it does promptly regenerate germinatively.

Any parasite is limited by the regeneration of its hosts and, at least on deep siliceous sands and quartzite alluvium, the hemiparasitic Nuytsia floribunda (https://www.inaturalist.org/observations/104204182) is a very rapid, vegetative regenerator after fire, limiting the opportunities for Cassytha at this stage.

Casytha glabella tends simply to maintain small but significant contribution to the foliage cover of the stand, through the cycle of fire and regeneration.

Cassytha micrantha re-establishes from seedlings within 2 y of fire (Newbey 1987), whereas C. melantha does not for at least two years (Newbey 1987). This difference can most parsimoniously be explained by the speed of regeneration of different strata and life-forms of hosts.

Where the marlocks (https://en.wikipedia.org/wiki/Marlock) favoured by C. melantha are killed by fire, the flush of pauciennial Alyogyne (https://www.inaturalist.org/observations?place_id=6827&taxon_id=71957&view=species) and Kennedia (https://www.inaturalist.org/observations?place_id=6827&taxon_id=71957&view=species) dominating the regeneration stands in the first few years after fire is free of this and all other parasites.

Cassytha does not appear to parasitise Nuytsia floribunda. This is true despite the two types of parasites coexisting, and mistletoes being known to parasitise other parasites, including other mistletoes.


All spp. of Cassytha in/near FRNP flower in spring. However, C. melantha finishes in October (Newbey 1987, pers. obs. 1991), whereas other spp. start in Oct.-Nov. and extend to January.

Cassytha glabella may have a particularly protracted flowering season (Newbey 1987), and was seen in fruit in/near FRNP in mid-November 1991 and late April 1992.

Cassytha cannot be considered an autumn fruiter, as are so many bird-dispersed plants of the temperate zone, including Syzygium, Punica, Crataegus/Cotoneaster, Carissa, and Psidium, all fruiting in May 1997 in Claremont-Newlands-Rondebosch, in Cape Town, as I analysed these field-notes.


Cassytha melantha:

See https://www.yarraranges.vic.gov.au/PlantDirectory/Climbers-Creepers/Cassytha-melantha

In/near FRNP, this species occurs in yate and mallee of Eucalyptus gardneri, in gorges,and on alluvia and coastal dunes. Its habitat tends to be base-rich. It occurs also in moort forest (Eucalyptus platypus).

Cassytha melantha forms the most substantial foliage (strand diameter 2 mm) and fleshy fruit found in this genus in or near FRNP.

Although the fruit does not seem to ripen to a bright hue or a sweet taste, it is too large to be moved far by ants, is not prone to dropping to the ground, and has a somewhat vis ours coating around the seed, suggesting dispersal by birds.

Cassytha melantha parasitises the canopy of tall, mature plants of Eucalyptus on relatively phosphorus-rich soils (where it may exceed 1% foliage cover in some stands). It is absent from oligotrophic landforms, even where Eucalyptus is abundant and reaches 4 m high, such as in mallee-heath in and near FRNP.

This species replaces mistletoes, which are virtually absent from south coastal Western Australia.

Like other parasites, it apparently benefits from physical disturbance of the stands of its hosts. It tends to be common only at the edges of stands of tall eucalypts. It was absent from the stands I examined of Eucalyptus occidentalis on alluvial levees of drainage lines. However, it was present in a stand of the same species at the disturbed edges of a swamp of paperbark Melaleuca.

The fleshy fruit of C. melantha is approximately similar in size to those of its host, Eucalyptus platypus (https://www.inaturalist.org/taxa/201389-Eucalyptus-platypus), as well as the mistletoes it apparently replaces in vegetation subject to canopy-wildfires.

Cassytha racemosa:

Cassytha racemosa is similar in the size and height of the plant, and in the size of the fruit, to Cassytha glabella. It does not contain alkaloids. It flowers in spring, as I noted in Nov.1991 in/near FRNP, and at Sheepwash Creek much farther to the west. It is well into its flowering season in November (pets. obs.; Newbey 1987), but was not fruiting in late Nov. 1991.

In/near FRNP, this species is recorded from coastal dunes, and RMC plots on laterite and limestone, but not in moort (Eucalyptus platypus) or Eucalyptus gardneri. However, in another table (?in Newbey 1987), it is listed from yate, Agonis, Eucalyptus angulosa, Eucalyptus pleurocarpa, thicket, and heath. It is possibly restricted to mature stands of vegetation.

This species may have relatively restricted occurrence in/near FRNP (Newbey 1987). However, I observed this or a similar form in Upland environments (where unrecorded by Newbey 1987), as well as on coastal dunes where a heath stratum was present.

Cassytha glabella:

This species is even more widespread than C. melantha (Weber 1981, Fox 1988). In/near FRNP it occurs in most habitats. It is typical of Eucalyptus pleurocarpa mallee-heath, and found in most other vegetation types including kwongan on siliceous sand (SS1 type) and RMC limestone type. However, it does not occur in Eucalyptus platypus forest.

Cassytha glabella favours Myrtaceae as hosts. In/near FRNP, it forms relatively small plants in low, small-leafed shrubs, often of Melaleuca, in the heath stratum, on oligotrophic soils.

Cassytha glabella flowers in summer. It produces its First fruits at the same time as its larger congener, C. melantha (e.g. late Nov. 1991, and I have a field-note stating end of April 1982, in mallee-heath, where the plant is fine-stranded and yellow). However, it tends not to coexist in the same stands as C. melantha, owing to ecological differences.

This species may be dispersed by small birds (e.g. Zosterops, see notes from Ian Rooke), but appears equally suitable for ants. Did Berg (1975) record it?

Both C. glabella and C. melantha have fruit-pulp that tastes rather resinous, possibly because of the 'resin' content of the Myrtaceae they parasitise.

Habitat differences between C. glabella and C. racemosa are unclear. The latter has fruits of similar size, and parasitises similar hosts, but apparently starts fruiting later in the season.

Cassytha micrantha:

See https://florabase.dpaw.wa.gov.au/browse/profile/2954

Cassytha micrantha is restricted to coastal southwestern Australia. Nowhere is it common.

In/near FRNP, it occurs on plains, in Eucalyptus pleurocarpa mallee-heath, in kwongan on siliceous sand (SS1 type), in RMC laterite plot, and in RMC limestone plot.

Cassytha micrantha is an extremely gracile, low-growing plant, tending to parasitise wiry sedge-like plants.

Brown and Hopkins (1983) recorded C. micrantha in kwongan in Tutanning Nature Reserve (https://www.pingelly.wa.gov.au/Profiles/pingelly/Assets/ClientData/Tutanning_Hut_-_Brochure.pdf), on laterite, sand and duplex substrate (sand over clay).

Cassytha micrantha flowers in summer, by mid- to late November (pers. obs., 1991; Newbey 1987), and started to fruit late in November (pers. obs. South Stirling, 1982).


In the Cape Flora of southern Africa, the only species of Cassytha is Cassytha ciliolata (https://www.inaturalist.org/taxa/461729-Cassytha-ciliolata). The fruits have diameter about 0.5 cm, which is not particularly large. However, the succulent fruits turn red, making them brighter-hued than any of the Australian spp. discussed here.

Cassytha pubescens (https://www.inaturalist.org/taxa/323806-Cassytha-pubescens) does not occur in/near Fitzgerald River National Park. However, it occurs under the mediterranean-type climate in South Australia, making it ecologically as comparable with Cassytha ciliolata of South Africa as are any of the spp. in/near FRNP.

Cassytha pubescens flowers in summer-autumn (Forde 1986).Its fruit has diameter 0.5-0.6 cm (data presumably from Weber 1981), which is larger than that of e.g. Cassytha glabella. However, based on dimensions given in Wikipedia, the fruit of C. pubescens is probably also larger than that of Cassytha ciliolata.

For the relative sizes, please see https://www.inaturalist.org/observations/101518388 vs https://www.inaturalist.org/observations/141352431.

The fruit of C. pubescens is greenish/reddish/black (Forde 1986). It is eaten by e.g. Dasyornis broadbenti (https://www.inaturalist.org/taxa/13481-Dasyornis-broadbenti), Gavicalis virescens (https://www.inaturalist.org/taxa/370319-Gavicalis-virescens), and Acanthagenys rufogularis (https://www.inaturalist.org/taxa/12677-Acanthagenys-rufogularis).

(This species does not contain alkaloids.)

Observations in iNaturalist show that the hues of the ripe fruit are subtle, rather than bright:


What emerges is that, although C. pubescens of southern Australia and C. ciliolata of southernmost South Africa are intercontinental counterparts, there is a difference in the conspicuousness of the ripe fruits. Although C. pubescens has the advantage of size, the red is so bright in C. ciliolata that its minimum brightness exceeds the maximum brightness of C. pubescens.

Ripe fruits of Cassytha ciliolata:



Many naturalists are familiar with Cassytha, particularly in the Cape Floristic region of South Africa.

However, many may not realise that

  • this genus represents an intercontinental pattern similar to the better-known pattern in Proteaceae, and
  • the bright red hue of the ripe fruits of the species in fynbos, namely C. ciliolata, is odd in the genus, which otherwise has fairly dull-hued fruits, some of them probably dispersed by ants rather than birds.
Publicado em 24 de novembro de 2022, 07:11 AM por milewski milewski | 19 comentários | Deixar um comentário

22 de novembro de 2022

Misleadingly similar solanums with different relationships to wildfire, in Australia vs southern Africa

@plantperson7654 @wojciech @aguilita @bryanconnolly @mjpapay @troos @botaneek @benjamin_walton @richardgill @sedgesrock @wynand_uys @venturefoth @adriaan_grobler @alastairpotts

Acknowledgement: Many thanks to Jeremy Gilmore @jeremygilmore (see comment in https://www.inaturalist.org/journal/milewski/72788-flora-of-fleshy-fruits-at-nature-s-valley-western-cape-south-africa#) and Tony Rebelo @tonyrebelo for information crucial to this Post.

Solanum symonii of southwestern Australia and Solanum guineense of southwestern South Africa are comparable. This is because both are centred on the mediterranean-type climate, and sandy substrates, mainly coastal.

They are similar in growth-form and fruit-form within the genus, despite belonging to different subgenera.

Solanum symonii is strictly confined to the mediterranean-type (winter-rainfall) climate. Solanum guineense is more versatile, extending somewhat into winter-rainfall semi-arid (Namaqualand) and bimodal rainfall (Eastern Cape). However, this is not a major difference.

Both are short-lived perennials growing to 1.5-2 m high. Solanum symonii tends upright with long leaves, S. guineense somewhat lax with shorter leaves. However, the differences seem unimportant.

Both spp. seem to lack spines on the leaves and stems (for relevance, see https://www.jstor.org/stable/2399203).

Both have smooth-skinned, succulent berries of approximately oval shape, and about 1.5 cm diameter. Solanum symonii tends to ripen to purple, whereas S. guineense tends to ripen to orange.

However, in the context of the great diversity of fruit-forms in genus Solanum (https://www.jstor.org/stable/23872220), this difference seems minor, and is unlikely to indicate a categorical difference in the animals, or range of animals, serving to disperse and sow the seeds.

Given these similarities, why is it that there is such a difference in the number of observations in iNaturalist?

There are currently only 10 observations of S. symonii, compared to 224 of S. guineense.

This may provide a clue to the real difference: that S. symonii is a post-fire (ashbed) specialist, whereas S. guineense bears no particular relationship to wildfire, and tends to occur in vegetation naturally protected from fire.

Rippey and Hobbs (2003, https://researchrepository.murdoch.edu.au/id/eprint/17081/1/effects_of_fire_and_quokkas.pdf) describe S. symonii as a 'fire ephemeral', living only about five years and then disappearing until the next fire.

To understand this fully, it is important to realise that the regimes of wildfire tend to differ in the relevant parts of the two continents. In southwestern Australia, the vegetation is relatively tall and 'resinous', burning intensely every several decades (https://www.academia.edu/7565234/Ecology_of_Australia_the_effects_of_nutrient_poor_soils_and_intense_fires). In southwestern South Africa, the vegetation is relatively short, burning with limited intensity on a relatively frequent basis - and tending to spare the littoral dunes with which S. guineense is particularly associated.

This difference is partly explained by the more profound and widespread nutrient-poverty in Australia than in southern Africa, exacerbated by the great difference in the incidence of large herbivores (https://www.researchgate.net/publication/229774801_Why_are_very_large_herbivores_absent_from_Australia_A_new_theory_of_micronutrients and https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-2699.2000.00436.x and https://www.jstor.org/stable/2656292).

This difference implies that there is a difference in the nature of the seeds: durable in the soil in the case of S. symonii, compared to non-durable in the case of S. guineense.

Although the agents of dispersal remain to be documented, I suspect that a significant difference is the role of Dromaius novaehollandiae (https://www.inaturalist.org/taxa/20504-Dromaius-novaehollandiae).

Please see https://www.malleeconservation.com.au/blog/emu-poo and https://data.environment.sa.gov.au/Content/Publications/JABG01P321_Symon.pdf.

This species differs fundamentally from Struthio camelus (https://www.inaturalist.org/observations/88050285) in its gastrointestinal system. Emus digest food extremely superficially (https://www.academia.edu/24722483/Emus_as_non_standard_seed_dispersers_and_their_potential_for_long_distance_dispersal). By contrast, ostriches digest their food so thoroughly that few seeds, including the small seeds of solanums, are likely to be defecated intact.

In summary, S. symonii seems to be a natural, indigenous 'fireweed' on a continent run by fire, whereas S. guineense has no particular relationship to fire, instead depending on a combination of relatively phosphorus-rich substrates and relatively intense disturbance by large animals.




















Scroll through images in https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:819387-1/images






Publicado em 22 de novembro de 2022, 08:23 PM por milewski milewski | 6 comentários | Deixar um comentário

21 de novembro de 2022

Why does the Mediterranean Basin lack a littoral effect in the incidence of fleshy fruits?

@tonyrebelo @ludwig_muller @jeremygilmore @benjamin_walton @botaneek @adriaan_grobler @yvettevanwijk1941

In the southern parts of southern Africa and Australia, there is a noticeable pattern involving fleshy fruits in the littoral zone (https://www.merriam-webster.com/dictionary/littoral).

Many spp. of plants, representing many families, bear fleshy fruits on beach dunes, rocky promontories, and other littoral environments (within a few hundred metres of the sea) in

  • the southwestern Cape of South Africa, and, to a lesser degree,
  • southwestern Western Australia, and southern South Australia and Victoria.

This tends to contrast with comparable substrates farther inland, where fleshy fruits tend to have minor incidence, even within the same genera.

Particularly striking examples of this pattern include:

However, there is no similar pattern in the Mediterranean Basin.

The only species with fleshy fruits that is consistently associated with the littoral is Corema album (Empetraceae). A typical specimen and situation is seen in https://upload.wikimedia.org/wikipedia/commons/0/0c/Camari%C3%B1as_cerca_del_cementerio_de_los_ingleses.png

This species has a rather restricted distribution in the western parts of the Basin (https://www.inaturalist.org/taxa/326752-Corema-album). Indeed, this distribution does not technically fall within the Basin in the first place, because the coast involved is that of the Atlantic, not the Mediterranean Sea.

As far as I know, there is also no littoral effect on the incidence of fleshy fruits in climatically comparable parts of California and Chile.

Here is a hypothesis in explanation of the littoral effect.

What sets Australia and southern Africa apart ecologically, among the various continental regions with a mediterranean-type climate (https://www.researchgate.net/publication/228019813_Mediterranean_Ecosystems), is the nutrient-poverty of the soils, and the widespread sandiness at the coast.

Fleshy fruit-pulp tends to be rich in potassium, and not other nutrient elements (https://www.jstor.org/stable/2844617 and https://www.jstor.org/stable/2389867).

The sea is a source of affluence of potassium in particular, because of the tendency for aerosols to blow inland from sea-spray (https://www.mdpi.com/2073-4433/9/8/298/htm#:~:text=Marine%20aerosols%20are%20comprised%20of,condensable%20atmospheric%20gases%20%5B2%5D.).

It can therefore be argued that fleshy fruits represent an adaptation to a relative surfeit of potassium, in the sense of an ample ratio of this cationic element to other nutrients such as phosphorus and zinc.

This surfeit would hypothetically not arise in the Mediterranean Basin, because

The sea-swell is also greater in coastal California and Chile than those in the Mediterranean Basin. However, here too, a surfeit of potassium may not arise, because the coastal substrates are likely to be even nutrient-richer than those in Europe and North Africa.

Publicado em 21 de novembro de 2022, 08:58 PM por milewski milewski | 19 comentários | Deixar um comentário

Flora of fleshy fruits at Nature's Valley, Western Cape, South Africa

In late May 2000, I investigated the vegetation around Nature's Valley (https://en.wikipedia.org/wiki/Nature%27s_Valley). My search-image was for plants with fleshy fruits.

In the following, I present an observation from iNaturalist as close as possible to Nature's Valley, followed by the clearest photo available of the ripe fruit, followed by my own field-notes from 2000.

Euclea racemosa (https://www.inaturalist.org/taxa/526223-Euclea-racemosa)

Euclea acutifolia (https://www.inaturalist.org/taxa/585511-Euclea-acutifolia)


  • There are currently no records of this species in iNaturalist, anywhere near Nature's Valley; however, I observed it here, in the fire-free dry scrub of Eriocephalus etc. on rocky slopes at the littoral, at the east end of Nature's Valley beach; extremely sclerophyllous for a member of the Cape Flora, qualifying as truly sclerophyllous according to a standard covering both Australia and southern Africa; I saw only unripe, developing fruits; these fruits were brown and tomentose, unlike the fruits of congeners; I subsequently noticed that one fruit of a herbarium specimen in the Bolus Herbarium had split, suggesting quasi-dehiscence

Euclea crispa crispa (https://www.inaturalist.org/taxa/599235-Euclea-crispa-crispa)

Diospyros dichrophylla (https://www.inaturalist.org/taxa/583883-Diospyros-dichrophylla)

Diospyros whyteana (https://www.inaturalist.org/taxa/541445-Diospyros-whyteana)

Pterocelastrus tricuspidatus (https://www.inaturalist.org/taxa/526208-Pterocelastrus-tricuspidatus)

Putterlickia pyracantha (https://www.inaturalist.org/taxa/524315-Putterlickia-pyracantha)

Mystroxylum aethiopicum aethiopicum (https://www.inaturalist.org/observations?taxon_id=600329)

Lauridia tetragona (https://www.inaturalist.org/taxa/588764-Lauridia-tetragona)

Cassine papillosa/peragua/Elaeodendron croceum

  • One or more of these closely-related spp. was common in the forests of the area, as recognised by shape and colour of bole; I saw one fairly ripe fruit

Cassine parvifolia (https://www.inaturalist.org/taxa/581793-Cassine-parvifolia)

Gymnosporia nemorosa (https://www.inaturalist.org/taxa/567065-Gymnosporia-nemorosa)

Sideroxylon inerme (https://www.inaturalist.org/taxa/362175-Sideroxylon-inerme)

Canthium inerme (https://www.inaturalist.org/taxa/559528-Canthium-inerme)

Apodytes dimidiata (https://www.inaturalist.org/taxa/489301-Apodytes-dimidiata)

Olinia ventosa (https://www.inaturalist.org/taxa/557509-Olinia-ventosa)

Chionanthus foveolatus (https://www.inaturalist.org/taxa/582167-Chionanthus-foveolatus)

Olea capensis macrocarpa (https://www.inaturalist.org/observations?taxon_id=524915)

Olea europaea cuspidata (https://www.inaturalist.org/observations?taxon_id=322082)

  • Not seen

Olea exasperata (https://www.inaturalist.org/taxa/578517-Olea-exasperata)

Carissa bispinosa (https://www.inaturalist.org/taxa/337799-Carissa-bispinosa)

Scolopia zeyheri (https://www.inaturalist.org/taxa/557693-Scolopia-zeyheri)

Halleria lucida (https://www.inaturalist.org/taxa/402272-Halleria-lucida)

Burchellia bubalina (https://www.inaturalist.org/taxa/320155-Burchellia-bubalina)

Grewia occidentalis (https://www.inaturalist.org/taxa/334567-Grewia-occidentalis)

Solanum africanum (https://www.inaturalist.org/taxa/526198-Solanum-africanum)

Solanum linnaeanum (https://www.inaturalist.org/taxa/363523-Solanum-linnaeanum)

(iNaturalist shows the presence also of the following spp. of Solanum in the area: https://www.inaturalist.org/taxa/594582-Solanum-rigescens and https://www.inaturalist.org/taxa/133287-Solanum-mauritianum and https://www.inaturalist.org/taxa/79143-Solanum-sisymbriifolium and https://www.inaturalist.org/taxa/472816-Solanum-tomentosum and https://www.inaturalist.org/taxa/326781-Solanum-retroflexum and https://www.inaturalist.org/taxa/169078-Solanum-pseudocapsicum and https://www.inaturalist.org/taxa/336677-Solanum-chenopodioides and https://www.inaturalist.org/taxa/79141-Solanum-nigrum and https://www.inaturalist.org/taxa/280892-Solanum-aculeatissimum and https://www.inaturalist.org/taxa/594574-Solanum-giganteum)

Knowltonia vesicatoria (https://www.inaturalist.org/taxa/596679-Knowltonia-vesicatoria)

Chironia baccifera (https://www.inaturalist.org/taxa/426224-Chironia-baccifera)

Cussonia thyrsiflora (https://www.inaturalist.org/taxa/566831-Cussonia-thyrsiflora)

Osteospermum moniliferum (https://www.inaturalist.org/taxa/404420-Osteospermum-moniliferum)

Capparis sepiaria (https://www.inaturalist.org/taxa/340365-Capparis-sepiaria)

Searsia crenata (https://www.inaturalist.org/taxa/593871-Searsia-crenata)

Searsia lucida lucida (https://www.inaturalist.org/taxa/593894-Searsia-lucida)

Searsia laevigata (https://www.inaturalist.org/taxa/493489-Searsia-laevigata)

Searsia glauca (https://www.inaturalist.org/taxa/564119-Searsia-glauca)

Searsia chirindensis (https://www.inaturalist.org/taxa/557697-Searsia-chirindensis)

Allophylus decipiens

Carpobrotus sp. or spp.

  • Local, uncommon

Morella quercifolia (https://www.inaturalist.org/taxa/590286-Morella-quercifolia)

Rhoicissus tomentosa (https://www.inaturalist.org/taxa/566441-Rhoicissus-tomentosa)

Rhoicissus digitata (https://www.inaturalist.org/taxa/593077-Rhoicissus-digitata)

Kedrostis nana (https://www.inaturalist.org/taxa/431200-Kedrostis-nana)

Zehneria scabra (https://www.inaturalist.org/taxa/607043-Zehneria-scabra)

Cassytha ciliolata (https://www.inaturalist.org/taxa/461729-Cassytha-ciliolata)

Colpoon compressum (https://www.inaturalist.org/taxa/527438-Colpoon-compressum)

Thesium fragile (https://www.inaturalist.org/taxa/1180365-Thesium-fragile)

Viscum obscurum (https://www.inaturalist.org/taxa/596023-Viscum-obscurum)

Viscum sp. indet.

  • Parasitic on Virgilia, also in fruit; seems different from V. obscurum, butnI cannot identify it from Polhill and Wiens

Viscum aff capense

  • Rare (one plant seen somewhere in the area)

Afrocarpus falcatus (https://www.inaturalist.org/taxa/136323-Afrocarpus-falcatus)

Podocarpus latifolius (https://www.inaturalist.org/taxa/132930-Podocarpus-latifolius)

Zantedeschia aethiopica (https://www.inaturalist.org/taxa/56006-Zantedeschia-aethiopica)

Chasmanthe aethiopica (https://www.inaturalist.org/taxa/361348-Chasmanthe-aethiopica)

Asparagus aethiopicus (https://www.inaturalist.org/taxa/75603-Asparagus-aethiopicus)

Asparagus setaceus (https://www.inaturalist.org/taxa/75604-Asparagus-setaceus)

Asparagus asparagoides (https://www.inaturalist.org/taxa/64107-Asparagus-asparagoides)

Publicado em 21 de novembro de 2022, 07:41 AM por milewski milewski | 18 comentários | Deixar um comentário

20 de novembro de 2022

Field-notes on the biology of Pterocelastrus tricuspidatus (Celastraceae), highlighting the puzzle of seed-dispersal

@dianastuder @tonyrebelo @jeremygilmore @ludwig_muller @botaneek @troos @benjamin_walton @vynbos @yvettevanwijk1941 @richardgill @dhoare @craigpeter @adriaan_grobler @koosretief @chris_whitehouse @robertarcher397 @sandraf @elmarvrooyen @geoffnichols @strandloper @alastairpotts

In and around May 2000, I visited West Coast National Park (https://en.wikipedia.org/wiki/West_Coast_National_Park), Gansbaai (https://en.wikipedia.org/wiki/Gansbaai), Nature's Valley (https://en.wikipedia.org/wiki/Nature%27s_Valley), and Addo National Park (https://en.wikipedia.org/wiki/Addo_Elephant_National_Park).

I made the following field-notes on Pterocelastrus tricuspidatus (https://www.inaturalist.org/taxa/526208-Pterocelastrus-tricuspidatus and http://pza.sanbi.org/pterocelastrus-tricuspidatus).


This is a shrub rather than a tree. It regenerates vegetatively (https://www.inaturalist.org/observations/14285413) rather than germinatively.

In West Coast National Park and at Gansbaai, the plants are only about 2 m high (https://www.inaturalist.org/observations/40291312 and https://www.inaturalist.org/observations/30876554).

At Nature's Valley, the plants are generally >3 m high. Presumably old specimens, 6 m high, are still multi-stemmed. The species is common in the afromontane forests at Knysna and Tsitsikamma (https://en.wikipedia.org/wiki/Knysna%E2%80%93Amatole_montane_forests), as well as occurring in coastal scrub.

The reddish wood is hard and dense (https://knysnawoodworkers.co.za/articles/characteristics-of-our-indigenous-trees/candlewood-pterocelastrus-tricuspidatus/#:~:text=The%20wood%20is%20beautifully%20marked,wood%20produces%20striking%20cathedral%20figuring.&text=The%20wood%20saws%20easily%2C%20despite,a%20smooth%20finish%20is%20obtainable.), similar to that of 'dwarf ebonies'. The species is reputed to be slow-growing, which also implies great longevity.

Leaf-size is variable. It is relatively small in West Coast National Park. However, it is relatively large at Nature's Valley (e.g. width 4.5 cm, https://www.inaturalist.org/observations/10785564 and https://www.inaturalist.org/observations/10947188). This holds true even in an extremely windy (but somehow not halophytic) situation, where P. tricuspidatus grows as part of a wind-shorn mat/hedge, 0.5 m high, of intermingled spp. of plants, at the edge of a pebble beach, e.g. near Salt River (https://en.wikipedia.org/wiki/Salt_River_(Nature%27s_Valley)).

Leaf texture:

The leaves are notably thickened. However, they conform to neither sclerophylly nor fleshiness.

The leaf is brittle, and can be carved easily with the thumbnail, at least in the case of the large-leafed form of the fire-free littoral. This differs from coexisting Sideroxylon inerme, which is truly semi-sclerophyllous (leaf is dry and not similarly brittle), even in littoral situations.

I would place the leaves of P. tricuspidatus as belonging to a separate category, 'designed to attract neither herbivory nor fire', but also palatable to Loxodonta africana (von Gadow, 1973) and Sylvicapra grimmia grimmia (https://www.inaturalist.org/observations?taxon_id=698822). In West Coast National Park, this plant is a preferred food of the latter antelope (Oom Dawid Bester, pers. comm., please scroll to the end of https://thenaturecollege.com/team/).

Flammability and relationship to wildfire:

The foliage of P. tricuspidatus is very flammable (Oom Dawid Bester, pers. comm.), which is puzzling in terms of adaptation.

I accept that this species is part of a fire cycle in relatively open forms of strandveld, as in West Coast National Park. However, in the area of Nature's Valley, the plant is free of wildfire, except perhaps once per century or so. I crushed the leaves, but could not detect any resinous smell. So, overall, I do not see that this species can be regarded as a fire-adapted plant, in the sense of Australian counterparts with a 'mallee' growth-form.

The literature states that the wood is very flammable, hence the name 'candlewood'. How does this work (resin canals)?

Fruiting phenology:

At Nature's Valley, the plants were in fruit, nearly full-size but premature, greenish-yellow, with a few flowers still apparent.

The episodicity of fruiting is striking.

I have been in the habitat of P. tricuspidatus repeatedly over the years, but have not encountered the fruits in any numbers until this autumn of 2000, leading me to realise that this is a 'mast-fruiting' species. A reference on the forests of the southern Cape states that the species flowers every year but only produces fruit every 2-3 years; I suspect that thus understates the episodicity of the fruiting. I found that the season at Nature's Valley was one month or more later than at Gansbaai. In retrospect, I should have looked under the shrubs in West Coast National Park for fallen fruits, since I saw the plants in full fruit only at Langebaanweg, leaving me wondering whether, in this Park, its fruiting was over, yet to come that year, or a non-event here despite its mast-fruiting elsewhere.

The bright hue of the fruits is conspicuous, particularly when the fruits are massed (https://www.inaturalist.org/observations/10896818 and https://www.inaturalist.org/observations/28484135 and https://www.inaturalist.org/observations/15940165), as they are in a 'mast' year. I now realise that the fully ripe fruits go beyond yellow-orange, to orange with a tinge of red. There is no pre-ripe display.

I noted that P. tricuspidatus was in fruit near Sedgefield (location near https://www.inaturalist.org/observations/11025916) in mid-September 2000.


This remains unresolved.

I made a special trip to ask Jack Skead (https://en.wikipedia.org/wiki/CJ_Skead) which spp. of birds eat the fruits of P. tricuspidatus, but he did not know. I also asked Carl Vernon (https://www.tandfonline.com/doi/pdf/10.2989/00306525.2021.1960020 and https://www.facebook.com/victorianheritage1905/posts/6202846636466994), who had years of experience in the habitat of P. tricuspidatus, and he did not know, apart from confirming that he had never seen any bird taking any interest in the fruits.

Books on southern African trees state that this species is difficult to grow, being a poor germinator. Oom Dawid Bester agreed, telling me 'it is as if the seed is dead'.

Rowan (1983, https://www.tandfonline.com/doi/abs/10.1080/00306525.1984.9634592?journalCode=tost20) mentions that Phillips recorded Tauraco corythaix (https://www.inaturalist.org/taxa/7205-Tauraco-corythaix) as eating the fruits of the genus Pterocelastrus. However, this leaves me wondering about the differences between rostratus (https://www.inaturalist.org/taxa/592662-Pterocelastrus-rostratus) and tricuspidatus, and whether the fruits were eaten ripe or green. After all, T. corythaix eats not only fruits but also buds of Ficus and flowers of Cussonia.

Phillips also compiled an extensive list of the spp. of fruits eaten by Columba arquatrix (https://www.inaturalist.org/taxa/3012-Columba-arquatrix), and Pterocelastrus is not among them. However, this fruit-eating columbid deserves further investigation.

Pterocelastrus tricuspidatus has repeatedly been recorded in the diet of Loxodonta africana near Knysna. This includes ripe, fallen fruits (https://www.inaturalist.org/journal/milewski/61207-plants-eaten-by-the-savannah-elephant-in-the-cape-floristic-region-part-2#).

However, it is hard to see this proboscidean as the main disperser and sower of the seeds. This is because

  • germination of P. tricuspidatus has not been observed in the faeces, and
  • L. africana is unlikely to be sensitive to the orange/red hues of the ripe fruits, and probably forages olfactorily rather than visually, anyway.

At Fairhill Private Nature Reserve (https://fairhill.co.za/) near Gansbaai, I watched several individuals of Taurotragus oryx oryx eating the ripe fruits of P. tricuspidata. I examined the fresh faeces for seeds. I found many fully intact seeds of Euclea racemosa, which was also in 'mast-fruit' at this location at this time. The landowner, Val Deverson, confirmed that she had observed the animals eating the ripe fruits of E. racemosa. However, I failed to find seeds of P. tricuspidatus in the faeces.


The enigma of dispersal and sowing of P. tricuspidatus is intriguing, because this plant is relatively widespread, and dominant in considerable areas of forest and scrub, in southernmost South Africa. A guide-booklet for Swartkops Valley Bushveld (Urton 1993, https://books.google.com.au/books/about/Plants_of_the_Swartkops_Valley_Bushveld.html?id=dTVFAAAAYAAJ&redir_esc=y) lists P. tricuspidatus, Euclea racemosa, and Sideroxylon inerme, among others, as typical members of this vegetation type.

I do not recall seeing P. tricuspidata in Addo National Park, but I suspect that it occurs in Bontveld on relatively poor soils on slightly elevated ground here. Readers, please check https://www.researchgate.net/publication/47296499_A_systematic_check_list_of_flowering_plants_collected_in_the_Addo_Elephant_National_Park.

Pterocelastrus tricuspidatus is one of the few spp. shared between dry strandveld (https://journals.co.za/doi/pdf/10.10520/AJA00423203_2374) in West Coast National Park (average rainfall about 300 mm per year) and the Tsitsikamma forest (>800 mm per year, https://en.wikipedia.org/wiki/Tsitsikamma_National_Park#).

In West Coast National Park, Boucher and Jarman (1977, https://www.tandfonline.com/doi/abs/10.1080/00359197709519916) show it to be one of the main components of broad-leafed scrub on sand, extending on to granite but not on to limestone, where Searsia longispina instead occurs (https://www.inaturalist.org/taxa/593892-Searsia-longispina).

Comparison of fruit with that of Putterlickia pyracantha:

Putterlickia pyracantha (https://www.inaturalist.org/taxa/524315-Putterlickia-pyracantha) coexists with P. tricuspidatus in coastal scrubby vegetation (https://www.inaturalist.org/observations/140781514), and belongs to the same family (Celastraceae). It was concurrently in fruit at West Coast National Park and Nature's Valley in 2000.

There are many photos of the fruits of both P. tricuspidata and P. pyracantha (e.g. https://www.inaturalist.org/observations/127498576 and https://www.inaturalist.org/observations/121068064 and https://www.inaturalist.org/observations/23509411) in iNaturalist. What is immediately obvious is that dehiscence is extremely expressed in the latter, but subtle and easily overlooked in the former.

Intrigued by this, I have compiled the following comparison between the fruits of the two spp.

The fruit of P. tricuspidatus (https://www.inaturalist.org/observations/141918224 and https://www.inaturalist.org/observations/141150869 and https://www.inaturalist.org/observations/140341231) is smaller, and usually less red, than that of P. pyracantha (https://www.inaturalist.org/observations/11091125 and https://www.inaturalist.org/observations/139127586 and https://www.inaturalist.org/observations/140150333 and https://www.inaturalist.org/observations/140643701).

Another difference is that the fruit of P. tricuspidatus is horned (https://www.inaturalist.org/observations/140571322 and https://www.inaturalist.org/observations/119132528), whereas that of P. pyracantha is smooth.

Each fruit contains only two seeds, compared to more than a dozen (wrapped in orange-hued arils) in P. pyracantha (https://www.inaturalist.org/observations/100394322 and https://www.inaturalist.org/observations/79527193).

The seeds are smaller than those of P. pyracantha, despite the difference in total number of seeds.

The fruit-wall is more succulent than that of P. pyracantha, and does not necessarily dehisce, even after one week in a packet of leafy sprigs.

The fruit is less affected by picking than are those of P. pyracantha: it retains its yellowish hue, despite drying out to non-succulence. By contrast, that of P. pyracantha dries and dehisces (https://www.inaturalist.org/observations/127662606 and https://www.inaturalist.org/observations/113436780 and https://www.inaturalist.org/observations/46214709), the outer surface of the capsule retaining a dull red hue (https://www.inaturalist.org/observations/140150330 and https://www.inaturalist.org/observations/96128646).

The aril is smaller (see second photo in https://www.steenboknaturereserve.org.za/wp-content/uploads/2021/05/Pterocelastrus-rostratus-PDF.pdf) than that of P. pyracantha (https://www.inaturalist.org/observations/133126093 and https://www.inaturalist.org/observations/141674995 and https://www.inaturalist.org/observations/82469682), and does not cover the seed entirely. The aril of P. tricuspidatus is more oily and less succulent than that of P. pyracantha.

The fruit-wall of P. tricuspidatus is only weakly succulent, loses some of its moisture if/when it dehisces, and contains arils that are non-succulent (although possibly moister than that of Acacia cyclops, https://www.agefotostock.com/age/en/Stock-Images/acacia-cyclop-aril.html). By contrast, in P. pyracantha, the fruit-wall is non-succulent (drying to definitely non-succulent when dehisced), but the copious arils are clearly succulent (and non-oily).

In P. pyracantha, the conspicuous hues (red outer surface of capsule, bright orange aril) and arillate structure of the fruit are clearly adaptive to dispersal and sowing by birds, such as Pycnonotidae (e.g. https://www.inaturalist.org/observations/35691747) and Coliidae (e.g. https://www.inaturalist.org/observations/135258890). Although the ripening process may seem complicated in transforming the fruit from https://www.inaturalist.org/observations/80707225 to https://www.inaturalist.org/observations/76068591, the identities of the agents of dispersal are fairly straightforward.

However, in the case of P. tricuspidatus, the nature of the adaptation may remain as puzzling today as it was two decades ago, when I wrote my field-notes. Does any reader know better?

Publicado em 20 de novembro de 2022, 12:42 AM por milewski milewski | 3 comentários | Deixar um comentário

19 de novembro de 2022

Why are fleshy fruits rich in potassium?

Fleshy fruits are those adapted for dispersal by animals larger than insects. They are extremely diverse in form and phylogeny.

One of the most consistent aspects of fleshy fruits is that their fruit-pulp tends to be rich in potassium, even where it is poor in all other nutrient elements.

This consistent richness of fleshy fruit-pulp is particularly noteworthy because the food-rewards - such as sugars, lipids, and vitamins - offered in this form by plants to seed-dispersers are remarkably variable. Some fleshy fruits are sweet, others sour; some are rich in ascorbic acid, others not; a few are oily, most not so; and this variation applies even within the category of succulent fruits (viz. those with fruit-pulp containing >80% water, so that any crushing results in the visible exudation of juice).

This pattern has yet to be explained in adaptive terms.

There are two broad possibilities, which are not mutually exclusive.

Firstly, it is possible that the main function of potassium in fruit-pulp is to promote turgor pressure, in aid of maintaining succulence. However, the main problem with this is that even naturally dry fruit-pulp, such as that of carobs (fleshy pods of leguminous trees and shrubs in the Fabaceae).

Secondly, it is possible that the main function of the potassium is to provide nourishment for the animal concerned. However, the main problem with this is that potassium seems to be one of the 'cheapest' elements, cycling rapidly through the body, lacking any significant reservoir in the tissues, being easily excreted in urine, and having mainly a simple electrolytic (as opposed to catalytic) function.

Publicado em 19 de novembro de 2022, 11:31 PM por milewski milewski | 9 comentários | Deixar um comentário