The flora of southern Africa is not diverse enough to emulate hollies, part 2

One of the overlooked aspects of the flora of southern Africa - which is renowned for its phylogenetic diversity ( - is a lack of any counterpart for the familiar hollies. That is to say, for any species combining leaf-spinescence with fleshy fruits.

In various ways, this lapse is a case of 'so near and yet so far'.

For example:

The species closest to qualifying is Drypetes natalensis ( and and, which belongs to Putranjivaceae. The 'juvenile' leaves are toothed but not quite rigid enough to be called spinescent, and the fruits are fleshy but tend to wrinkle and harden when ripe. Less ambivalent is a congener in the Caribbean, Drypetes ilicifolia (

The failure of southern African floras to produce any species unambivalently combining leaf-spinescence with fleshy fruits can best be understood by comparison with Australia, where climates and soils are most aligned.

Even in Australia, the area with winter-rainfall and dry summers virtually lacks species with the combination in question. This is clearest in Ericaceae. Several endozoochorous ( genera occur in Western Australia, but the fruits are small and dull, and more attractive to ants than to seed-dispersing birds.

It is only in the eastern states of Australia - where the soils are slightly richer and rainfall occurs in both summer and winter - that the combination shifts towards recognisable form (e.g. and The most spectacular examples are in gents Leptecophylla (

The ericaceous genus Leucopogon nicely exemplifies this pattern. Under a winter-rainfall climate, several species are leaf-spinescent, and one species has bright-hued fleshy fruits ( However, no species combines these features - the closest being Leucopogon parviflorus ( with its small whitish fruits.

It is eastward - where rain falls year-round and a degree of geological uplift has slightly rejuvenated the soils - that the combination arises ( and and and and

Whereas transitional climates and soils cover an extensive area in five states of Australia, they cover only a small area in South Africa, mainly in Eastern Cape province ( The chances of a suitable niche arising have been correspondingly greater in Australia than in southern Africa.

And so even a flora as diverse and phylogenetically resourceful as the Cape Flora - producing one of the floristic 'kingdoms' of the world - has not found a suitable opportunity for evolutionary convergence with the familiar hollies of the northern hemisphere.

Posted on Πέμπτη 17 Φεβρουάριος 2022 00:34:47 UTC by milewski milewski


Αναρτήθηκε από milewski πάνω από 1 χρόνo πριν (Αναφορά)
Αναρτήθηκε από milewski πάνω από 1 χρόνo πριν (Αναφορά)

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