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The following Post is based on analyses conducted by the late Bill Foulds, author of https://nph.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-8137.1993.tb03901.x and https://www.jstor.org/stable/2558261 and https://library.dbca.wa.gov.au/static/Journals/080050/080050-01.004.pdf.
INTRODUCTION
Western Australia is nutrient-poor. The indigenous plants are accordingly adapted, by tending to have evergreen, nutrient-poor foliage.
These plants defend themselves from herbivory/folivory mainly by means of fibrousness (sclerophylly) and tannins (which, like fibre, contain only carbon, hydrogen, and oxygen, https://en.wikipedia.org/wiki/Tannin), rather than by defensive compounds that contain nutrient elements.
However, the flora contains many plants that supplement their supplies of nitrogen, by means of microbial nitrogen-fixation, hemi-parasitism, or 'carnivory'.
This suggests that these plants might tend to contain defensive substances based on amino acids (which contain nitrogen) and cyanide (the molecular formula of which is HCN, viz. a combination of equal parts of hydrogen, carbon, and nitrogen).
RESULTS
The following is information on the incidence of alkaloid-containing and cyanogenic plants (including non-indigenous spp.) in southwestern Western Australia, in relation to the nutrient status of soils. (In the case of Styphelia and Cakile, the analysed values range from negative to strongly positive.)
The strongly alkaloid genera were
The strongly cyanogenic genera were
In the case of legumes other than Acacia, Lotus (https://www.inaturalist.org/observations?place_id=6827&taxon_id=47436&view=species) and Trifolium (https://www.inaturalist.org/observations?place_id=6827&taxon_id=51876&view=species) were found to be cyanogenic, and the former also contained alkaloids.
However, cyanogenic spp. also occurred in
A wide variety of plants on coastal dunes was cyanogenic. This included Banksia woodland on the Swan Coastal Plain (https://en.wikipedia.org/wiki/Swan_Coastal_Plain).
The flora on sand dunes at Hillarys (https://en.wikipedia.org/wiki/Hillarys,_Western_Australia) was notably rich (27% of spp. sampled) in alkaloid-containing plants. including a succulent introduced from South Africa, viz. Tetragonia decumbens (https://www.inaturalist.org/taxa/560154-Tetragonia-decumbens). However, Exocarpos in this environment lacked alkaloids.
No alkaloid-containing plants were recorded in woodland (sampled at Hepburn Heights, https://en.wikipedia.org/wiki/Hepburn_Heights_bushland) of Banksia (https://www.inaturalist.org/observations?place_id=19379&taxon_id=64518&view=species) and Eucalyptus gomphocephala (https://www.inaturalist.org/taxa/162753-Eucalyptus-gomphocephala) on coastal sand.
In each plant community sampled near Perth (https://en.wikipedia.org/wiki/Perth#:~:text=The%20metropolitan%20region%20is%20defined,of%20Serpentine%2DJarrahdale%20to%20the), only one species (of the hemi-parasitic genus Cassytha, https://www.inaturalist.org/taxa/851590-Cassytha-flava) was found to contain alkaloids.
In the case of the hemi-parasitic genus Cassytha,
Woodland of Eucalyptus salmonophloia (https://www.inaturalist.org/taxa/499438-Eucalyptus-salmonophloia), under a semi-arid climate (https://en.wikipedia.org/wiki/Great_Western_Woodlands), was particularly rich in hemi-parasitic plants (particularly as sampled near Yellowdine, https://en.wikipedia.org/wiki/Yellowdine,_Western_Australia).
The hemi-parasite Exocarpos (https://www.inaturalist.org/taxa/525357-Exocarpos-aphyllus) contained alkaloids, but mistletoes did not. The mistletoes referred to are
The incidence of cyanogenetic plants in this woodland was less than in Banksia woodland under a mesic climate.
DISCUSSION
Many Acacia spp. are known to be cyanogenic.
The overall pattern seems to be that
There seems to be a lack of cyanogenic plants in mediterranean-type climates in which frost occurs. There may also be a lack under arid climates, but the pattern is unclear.
Why do grasses feature cyanogenesis but not alkaloids?
ACKNOWLEDGEMENT
I am grateful to the late Bill Foulds for sharing his data with me, and for discussing the patterns.
RAW DATA: PHOSPHORUS IN SOILS
The following refers to concentrations of phosphorus (parts per million) in topsoils.
RAW DATA: CYANOGENIC PLANTS
The following numbers of spp. were analysed for cyanogenesis in the various plant communities:
Semi-arid climate adjacent to mediterranean-type climate:
Dry form of mediterranean-type climate:
Mesic form of mediterranean-type climate:
Incidence of cyanogenic spp.:
Zero in all cases, except for banksia woodland (8.3% of analysed spp.) and sand dunes (31.6% of analysed spp.)
RAW DATA: ALKALOIDS
In each case, the first value is the no. of spp. analysed, and the second is the percentage of these found to contain alkaloids.
Semi-arid climate adjacent to mediterranean-type climate:
Dry form of mediterranean-type climate:
Mesic form of mediterranean-type climate:
Comments
https://www.sciencedirect.com/science/article/abs/pii/0378874194900922
https://www.inaturalist.org/taxa/481922-Lysiana-exocarpi
https://watermark.silverchair.com/24-4-447.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAA1wwggNYBgkqhkiG9w0BBwagggNJMIIDRQIBADCCAz4GCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMkuKktrdj2ejSSGMeAgEQgIIDD0Y7ZrVpAY9ifqMdf2Ng6-HjtyJ9P0Nqs2yBxcr2cydDBTDH3AlJu2EWbULGRkoaXRTDSv04yZtbSZzisWhyYm3Nzss3sGCpnolrGHxeEs6R5FIB5AAhHPOqB9wlkMOL4XaE5vzYxN9JeyEDvnM4Uz0ArZKsgQ2y65VV2QASuReCtMx6Yshq0L_tdCP-I_yTlbBQeD_r83e75WdAYgA_A8Bh0jWMEDPtFRNd-gI_i1dn5QuvFX5pE0dD9r_4exkimYkvUY6KOM8_SC8gngrw1xh4wkdsR2Zg4fSb8gPCSxlQMj_tm0YlwQ3P6j4NO6AGWHOScWJlSuhgkHLTIl7TW__Z0ISGCE_Nv6puJkxWBObAnTPRm5yk6ptS5u9Dbf6B-TEv_yaJ9VwVwiR2SXBfj97Zsz9UduI2MP6LCdoXTc1wxdt6QXHuQE4BF22sKs9oXauNY9llwS8Ocni4JtWSn6Jw8ljryxlRC9DFEYItRzKhSFHuSnVNlvOR325rJ-qaUmy_xuNK-eKJwBLiubvqN2QOg5KV9bqllgvvfOZqX9rg5JYHWC59owJafJhqwuqf7NUXaDJJp2coAfPzL9BiBWpQcIh6BLm930mHR3kcWUUMIzurh1YKj1VINazM1VLm8Zmnw0AueTYZGkvsC8EqLxp9CHndJdEjnR0vfys3lSV-hdBHax33WpWhI2BD-AqGIJM74i4x2Fp83EKVJ4F2Hs9GdzrNQPo-lNolmGxliCxs_sEpojcr9grQeXwD-eqCgDPjjhkhEBrUxbtY7iscPQn2mUCFrJpyR5NgR1IcmoaK-NiJqsZJdWaQdixWQe5TFy_ZuBGTxWE9IR2w44FY4CLOZ3GOGZf7C8C0z3XhrAIvN2IESf55Cj6Q1veR2vc2EclDqPDQrIsIBG7Me_BCKpBSodvKS2XM56l5pZoAG7atPfH9dnm6UqUiqYzjj5RmmtIQ1iumhAmOQPmkdyK6kpIIwBZW9Y0va1yqvPRR9edYSdJKyqs0Thp8vMEvgEdSFzCEP1OCYW_49AeWu4JARQ
Thankyou Anton, very interesting!
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