Re: How old are the aroids?
- Subject: Re: How old are the aroids?
- From: brian lee <firstname.lastname@example.org>
- Date: Tue, 29 Jul 2008 09:44:56 -0700 (PDT)
Wonderful line of thought...and it proves that we have so much more to learn.
Just a question...where have the earliest aroid fossils been collected? Do these preserve reproductive structures? Are you aware of the earliest fossils that preserve such structures and what do they reveal?
--- On Mon, 7/28/08, Peter Boyce <email@example.com> wrote:
> From: Peter Boyce <firstname.lastname@example.org>
> Subject: [Aroid-l] How old are the aroids?
> To: "Discussion of aroids" <email@example.com>
> Date: Monday, July 28, 2008, 8:55 PM
> As part of our aroid research here in Malaysia we are
> beginning to turn our thoughts to the age of our favourite
> family by, among other ways, analysing the modern
> distributions of related ever-wet or perhumid tropical
> forest herbs with restricted fruit/seed dispersal syndromes
> (e.g., insect dispersed short-viability seeds), such as
> Schismatoglottis sens lat., and then looking at tectonic
> plate movements to speculate about when the currently
> disparate taxa (or their hypothetical ancestor/s) were
> adjacent on a single landmass that permitted dispersal into
> areas that are now widely distributed (i.e., South America,
> Africa, the Indian Subcontinent &
> While clearly this method involves severe limitations and
> requires a rather uncomfortable number of assumptions about
> the origin and more criticall the evolutionary stability of
> dispersal systems, and of course much needs to be tested
> post-hypothesis by using more robust techniques, to date
> the 'results' are fascinating, to say the least.
> Perhaps for us (working as we do on a group with one of the
> most complex inflorescence morphologies in the family, if
> not in the entire plant kingdom and thus using orthodoxy an
> 'advanced' and by inference 'recent' group)
> the most exciting aspect of these ponderings has been that
> while focus on the age of the aroids has tended to indicate
> that the bisexually-flowered genera with 'primitive'
> paleoherb growth morphology (in essence the helophytic
> lasioids - as championed by Hay & Mabberly) or the
> equally 'primitive' Proto-aroids (that is to say
> the Orontiodeae + Gymnostachyoideae) are basal-most in the
> modern lineage and, particularly given recent fossil
> publications on late Cretaceous orontiods giving a modern
> subfamily origin at least 70mya, closest in appearance to
> the ancestral 'protoaraceae' it now seems that the
> schismatoids (that this Schismatoglottis sens lat.+
> Cryptocoryne) share a common ancestorat least 150 myo and
> given their modern floral complexity and their
> unisexual-flowered 'advanced' inflorescences raises
> issues about the aroids not only in terms of whether
> bisexual flowers are indeed 'primitive' but also in
> terms of just how old IS this family.
> Currently there are no indispudibly confirmed angiopserm
> fossils from earlier than the early Cretaceous; however
> already there a modern subfamily of the aroids from almost
> as early as the earliest known flowering plant fossils and
> indirect evidence that at least one modern tribe of the
> family has its origins from slightly earlier and THAT tribe
> is currently considerd to have (in modern taxa) one of the
> most complex inflorescence morphologies in the family....
> food for thought.
> Peter & Sin
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