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Re: Mesozoic birds made insects shrink



Does this suggest that pterosaurs had a negligible effect on insect sizes?


On Tue, Jun 5th, 2012 at 5:09 AM, Ben Creisler <bcreisler@gmail.com> wrote:

> A new online paper:
> 
> Matthew E. Clapham and Jered A. Karr  (2012)
> Environmental and biotic controls on the evolutionary history of
> insect body size.
> Proceedings of the National Academy of Sciences (advance online publication)
> doi: 10.1073/pnas.1204026109
> http://www.pnas.org/content/early/2012/05/25/1204026109.abstract?sid=c6e6d409-6213-4580-
b946-19f7f4c13ea4
> 
> Abstract
> Giant insects, with wingspans as large as 70 cm, ruled the
> Carboniferous and Permian skies. Gigantism has been linked to
> hyperoxic conditions because oxygen concentration is a key
> physiological control on body size, particularly in groups like flying
> insects that have high metabolic oxygen demands. Here we show, using a
> dataset of more than 10,500 fossil insect wing lengths, that size
> tracked atmospheric oxygen concentrations only for the first 150 Myr
> of insect evolution. The data are best explained by a model relating
> maximum size to atmospheric environmental oxygen concentration (pO2)
> until the end of the Jurassic, and then at constant sizes, independent
> of oxygen fluctuations, during the Cretaceous and, at a smaller size,
> the Cenozoic. Maximum insect size decreased even as atmospheric pO2
> rose in the Early Cretaceous following the evolution and radiation of
> early birds, particularly as birds acquired adaptations that allowed
> more agile flight. A further decrease in maximum size during the
> Cenozoic may relate to the evolution of bats, the Cretaceous mass
> extinction, or further specialization of flying birds. The decoupling
> of insect size and atmospheric pO2 coincident with the radiation of
> birds suggests that biotic interactions, such as predation and
> competition, superseded oxygen as the most important constraint on
> maximum body size of the largest insects.


-- 
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Dann Pigdon
Spatial Data Analyst               Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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