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Re: (was marine reptile McMenu)


I'm pretty sure the paper is:
Karl J. Niklas. Patterns of Vascular Plant Diversification in the Fossil
Record: Proof and Conjecture. Annals of the Missouri Botanical Garden, Vol.
75, No.1 (1988), 35-54.

Niklas's study actually used change in species, genus and families. His discussion might be useful.

There have been a few other attempts to do this with plants, but I'm not as familiar with them. The ones of which I have heard showed a similar pattern of decreasing ?genus? life spans (even though the average estimates for species life-spans were as much as three times greater in one of the models).

There is a lot of potential bias due to increasing morphological complexity (allowing separation into more morphospecies), founder morphologies (leading to diversity among earlier forms being described in higher ranks) and novel adaptations (angiosperms sometimes speciate soley in order to better adapt to a new pollinator). Of course, these changes themselves might also restructure global ecosystems and background evolution, extinction and radiation patterns.

I personally suspect that increasing invasibility of ecosystems (globally) due to the Angiosperm radiation, may have been a major driving
factor in faunal turnover (but I have yet to think of a good way to test this).


-Jonas Weselake-George

----- Original Message ----- From: "David Marjanovic" <david.marjanovic@gmx.at>
To: "DML" <dinosaur@usc.edu>
Sent: Friday, February 29, 2008 8:04 AM
Subject: Re: marine reptile McMenu

- Changes in ecosystem level evolutionary process driven by keystone
species (eg. something like what we see in increasingly shorter genus
life spans among plants).

Do you have a ref for this? Because I'm writing a paper on phylogenetic nomenclature right now*, and I'd like to include this as an example of how ranks meddle with people's heads -- and picking on Benton** all the time would be unfair.

You see, there is no way to tell if something is a genus. Anyone can all
anything they want a genus, and nobody has a quantifiable criterion for
it, so there's not even a way to tell if it's consistent within a single
author's single classification. It follows logically that it is completely
impossible to compare the lifespans of genera. If anything, decreasing
genus lifespans tell us something about the classificatory practices of
paleobotanists, but not about biology.

* Still not my long-promised definition of Aves, unfortunately.
** Has published lots of studies where he, sometimes with a coauthor or
two, tried to quantify changes in biodiversity through time by counting
genera, families and/or orders. He's also a famous vertebrate
paleontologist, and publishes a lot. So he's the first who came to mind.