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  How old are the aroids?
From: botanist at malesiana.com (Peter Boyce) on 2008.07.28 at 23:55:20(18280)
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' inflores
cences 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

From: ted.held at us.henkel.com (ted.held at us.henkel.com) on 2008.07.29 at 09:34:04(18286)
Peter and Sin Yeng,

Not only are your comments food for thought, they are astonishing. You are
hinting that aroids are as old as any flowering plants, and you also
believe that they are at least as old as the earliest surviving angiosperm

Of course, we all know that if you want to be a fossil it helps to have
hard, durable parts that can be preserved long enough to be covered in
sediment and whatnot. I know from my own plants that preservation of
deceased material in warm, humid environments for more than even a couple
of hours is problematic. This means that the existential history of many
aroids and other life forms can have proceeded along for eons under the
fossil radar. Is this a way of teasing out some of the secret history of
the living world?

I am intrigued by your methodology. This thread also meshes with our other
recent discussion of the threatened-species nature of taxonomists, since
you seem to rely on inferences based on traditional taxonomy. Maybe if
young potential botanists think that there's more to it than pressing and
cataloging dry old plant parts they would more readily sign up. Also,
funding is nine parts show biz, so conjectures like this might stir up a
few bucks for deserving researchers.

Please keep me (us) updated on your thinking.


From: lbmkjm at yahoo.com (brian lee) on 2008.07.29 at 09:44:56(18287)
Dear Pete,


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?



From: crogers at ecoanalysts.com (Christopher Rogers) on 2008.07.30 at 10:37:43(18295)
Hello Peter and Sin Yeng,

I understand your difficulties! I wrote a paper a few years ago revising a
genus of freshwater shrimp. There are three species in the genus, all found
in rain pools on a very specific geomorphic surface: one species in North
America, one in South America, and one in Europe and north Africa. The
geomorphic settings are all very old, and at one time before continental
drift, were all near each other at the equator. Using this I could estimate
the age of the genus. So here is my question: are any ?primitive? aroid taxa
limited to certain geomorphic features that can be traced through history?
It may give you a means of estimating evolution rates for some higher taxa



From: lbmkjm at yahoo.com (brian lee) on 2008.07.30 at 13:39:40(18297)
Dear Ted, Sin Yeng, and Pete, etc.,


Sounds like we need to find an Early Cretaceous or older, aroid lagerstatten. Lagerstatten are fossil sites of exceptional preservation or completeness. China is discovering quite a few new sites... Perhaps someone needs to be looking at new Jurassic floras.



From: botanist at malesiana.com (Peter Boyce) on 2008.07.30 at 16:02:39(18298)
Hi Julius, Leland, Ted & friends

The Pistia-like thing was Cobbania corrugata, indeed a pistia-like aroid
from the lower Cretaceous (subfamily Cobbanoideae). There is another
intriguing plant, Limnobiophyllum scutatum (Limnobiophylloideae) also from
the Cretaceous. What is NOT known about eiher of these is these genera have
bisexual flowers (as in Lemnoideae) or unisexual flowers as in Aroideae
including Pistia.


From: botanist at malesiana.com (Peter Boyce) on 2008.07.30 at 23:54:43(18300)
Hi Christopher,

The 'best fit' for this is the Lasoideae with Anaphllopsis on the Guiana Shield, Lasimorpha in West Africa Anaphyllum in S. India

very best


From: epiphyte1 at earthlink.net (Adam Black) on 2008.07.31 at 09:35:23(18306)
Leland and all interested,

Aside from a lagerstatten site, don't forget about paleopalynological research analyzing fossil pollen, which as understand it would be more reliably preserved than other plant tissues. Well preserved leaves and other parts would of course be more intereting to visualize, but fossil pollen would be more likely to indicate the presence of aroids in paleoenvironments not conducive the preservation of leaves and other parts.

See the following, an interesting paper on pollen of an early Cretaceous Aroid from Portugal


Also here is an abstract of a late Cretaceous Aroid infructescense (J. Bogner one of the authors)


Also of interest, an Eocene Philodendron sect Meconostigma from western Tennessee:


...and another paper on fossil Araceae pollen:


These all jumped out at me on a quick Google search - but there is probably more info out there. I'm interested in fossil vertebrates of the Tertiary and Pleistocene and in research have noticed fairly regulary references to Tertiary aged Aroids, especially in the Eocene floras, but never looked earlier than that until now.

Adam Black

From: lbmkjm at yahoo.com (brian lee) on 2008.07.31 at 10:22:42(18307)
Dear Christopher and all,


Wow. There must have been some sort of refugia all that time to preserve your geomorphic features for the habitat of your shrimp. I would assume that is rare. What is the geologic history of the sedimentation or other processes of the region? Are we talking about Anostracan crustacea? I know you wrote a paper on fairy shrimp in Minas Gerais...could you resend me the pdf off forum?...I seem to have lost that to virtual world. Anostracans have a geologic history from the Lower Devonian, according to my Treatise on Invertebrate Paleontology. I do not recall the age of your geomorphic features...could you refresh my poor memory? I am most familiar with the Santana formation fossils of the Late Cretaceous of Brazil...when shallow seas or lacustrine environments existed....and the connection to African fossils of similar age are proven. I am assuming your geomorphic features predate that....perhaps by a significant period.

This is a very interesting point you bring up regarding tectonic movements and botanical evolutionary trends. Are there many references on the biogeography of the aroids?



From: lbmkjm at yahoo.com (brian lee) on 2008.08.02 at 11:52:58(18314)
Dear Adam and all,


Thank you for forwarding this information. From what I read, the fossil aroid record is sparse and the speculative interpretation is high. Very interesting. I do not know much about palynology and less about paleopalynology...it amazes me that so much information can be extracted from these tiny grains.

Being an optimist and the fact that many paleontologists are looking at Jurassic deposits, I am still hopeful that earlier proto-aroids will be discovered. It seems improbable that such plants suddenly appeared so fully formed in the Early Cretaceous. Time and new discoveries will tell.

I was very interested in the article you sent on a so-called Philodendron subgenus, Meconostigma...Philodendron limnestes, Dilcher & Daghlian 1977. I found out that Mayo, in 1991, thought this fossil was closer to the genus, Typhonodorum , tribe Peltandeae based on the venation and cuticular features.

Thanks again for the interesting leads.



From: crogers at ecoanalysts.com (Christopher Rogers) on 2008.08.05 at 08:53:14(18328)
Thanks, Peter!

Is that sufficient to establish a molecular ?clock??

D. Christopher Rogers

From: crogers at ecoanalysts.com (Christopher Rogers) on 2008.08.05 at 09:03:19(18329)
Aloha, Leland!

I will send you that, the biogeographical papers and some of my other papers off line. You are welcome to any of my publications, of course!

Yes, they are my beloved anostracans, notostracans and clam shrimps as well. I also have the book you mentioned with the chapters by Paul Tasch. So far most of the anostracan fossils have turned out to be other things like mayfly nymphs with all their abdominal gills. Some Russians have published a few papers claiming that they have anostracan fossils back to the cretaceous, however, my understanding is that the papers have not been peer reviewed, were published in less than 50 copies, and are not available outside their institutes. I have been trying for many years to acquire the texts, with no success. The only reliable fossil anostracan I am aware of is from the Miocene.

The animals that I mentioned in my last missive are the genus Phallocryptus, which are found in salars. The south American beast is in the salars near Buenos Aires.

I know this is waaaaaaaaaaaaaay off Aroids. So if anyone else is interested in my crustaceans, we can continue this topic off line.



From: botanist at malesiana.com (Peter Boyce) on 2008.08.05 at 22:51:05(18334)
Not alone, but with the addition of external data from modern distributions, molecular work and subsequent mapping, plus time line molecular work we can begin to get a handle on the family origin. The one thing that is irrefutable is that the aroids are at least early Cretaceous.

I was hoping that this thread would ellicit more responses on aroid-l than it has!


From: lbmkjm at yahoo.com (brian lee) on 2008.08.06 at 12:43:13(18341)
Dear Pete and all,


Perhaps Dr. Ruth Stockey is lurking about on aroid-l...she and I have corresponded offline...we had a common connection with Betty
Speirs, an amateur fossil researcher of a site called Joffre Bridge in Red Deer, Alberta. Betty is no longer with us, but Ruth is in charge of her collections of fossils from Joffre Bridge. I am sure you know Ruth and her husband,Dr. Gar Rothwell...and their publications on fossil Araceae, including Cobbania.

If we do not hear from her, I'll drop her a line and see if we cannot include her on this discussion. She may be on summer vacation.



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