From: lbmkjm at yahoo.com (brian lee) on 2008.07.29 at 16:44:56(18287)
Dear Pete,
Aloha.
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?
Aloha,
Leland
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--- On Mon, 7/28/08, Peter Boyce wrote:
> From: Peter Boyce
> Subject: [Aroid-l] How old are the aroids?
> To: "Discussion of aroids"
> 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 &
> Sunda/Wallacea/Melanesia).
>
> 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
> Yeng_______________________________________________
> Aroid-L mailing list
> Aroid-L at www.gizmoworks.com
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