>So, is there any thought on the place of origin for _Drosera_, or the
>_Droseraceae_, Jan?
There is some thought (BTW: I hope you did not want to insinuate by the
address that I am the only creature supposed to *think* on this list?!),
but I doubt there is agreement (or even knowledge). The problem is
certainly even more complicated than in Lentibulariaceae because
Droseraceae is a much older (how old??) family, and we have to expect many
relict distribution patterns, not necessarily illustrating the course of
evolution very clearly. The fossil record is poor, only some pollen being
known (neither from surprising localities). Thus, most phylogenetic
reasoning must rely on recent species (i.e. remain +/- speculative).
There is no agreement which family should be closest to Droseraceae. Some
of the most important features for familial classification (placentation,
pollen morphology) are transformed even within the family, and the
differences (in morphology, and therefore supposedly also in distribution;
also, molecular biology has not helped much, yet) are so great nowadays
that we can assume it would not help to elucidate the origin of Droseraceae
even if we knew their closest relatives.
J.Degreef puts it as a fact that _Drosera_ originated in S America and S
Africa, which is not substantiated further in his paper (in a recent
edition of the Bulletin of the AU CP SOC.). Maybe he is impressed by some
rather archaic (=paleoendemic?) species which do inhabit these regions
nowadays (_D.sessilifolia_, _D.regia_, BTW: I doubt the "primitive" status
and close relationship to any New Zealand species of _D.uniflora_).
Australia is certainly a (possibly secondary) centre of diversification of
_Drosera_ (many endemic or subendemic species and sections; =neoendemic?).
The (morphologically and geographically) closest genus being _Aldrovanda_,
we can not even be sure _Dionaea_ (which is possibly older than both!) has
had a common origin (i.e. already distinct from _Drosera_).
The presence of _Drosera_ in N America, Europe and temperate/boreal Asia
seems to be a rather "modern" feature, and maybe the genus was even
completely absent from these regions before Pliocene (Note: I do not have
any proof for this! Just ruminating...). I have demonstrated why I think
that the temperate species did spread from (S-) C via N America, already.
_Drosophyllum_ is apparently the most primitive member, and it is even
possible that the family is paraphyletic, i.e. some other genera (which are
now grouped with other families or extinct) might have split from the
"stem" between the "node" of _Drosophyllum_ and those of the other
Droseraceae.
Nevertheless, we can call it a fairly natural family (with the mentioned
reservation). But if we accept this, it becomes somewhat difficult to
explain the "southern" origin of _Drosera_ (i.e. either in the region
mentioned by Degreef or in Australia/New Zealand. However, the difference
does not matter that much if time is considered...) without assuming
substantial remodelling of range extensions or extinction in the past.
You see, there is not much we (or at least I) do really know.
Or can someone tell us more?
Kind regards
Jan