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In a recent paper in the Royal Society Proceedings B, Randy Irmis and Jessica Whiteside verify a prediction of the CEG model regarding earliest Triassic terrestrial communities of the Karoo Basin in South Africa. Ken Angielczyk and I were interviewed by Wired Science for an article about the paper. Read it all here!

We predicted that communities in the Lystrosaurus Assemblage Zone would exhibit intrinsic instability in the face of even mild disruptions of primary productivity. More recently (and here), we explained that the intrinsic instability stemmed from the rapid diversification of small to medium-sized synapsid carnivores in the aftermath of the end-Permian mass extinction, coupled with very low species richness of herbivorous tetrapod prey, and the resulting intensity of competitive interactions among the carnivores. The recent Proceedings B paper seems to support our prediction on the basis of relative abundances of species of different trophic ecologies, characterizing those species as “boom and bust”. It’s always great to have model verification!

I think that there are some unresolved questions though:

  1. We also suggested that one way out of the conundrum would be the increased specialization of the carnivores. Contrary to Irmis and Whiteside, I don’t agree that uneven relative abundances necessarily lead to demographic boom and bust cycles. Community dynamics are more nuanced and flexible than that.
  2. The authors also point to probable environmental instability based on carbon cycles (measured as carbon stable isotope signatures). They valiantly overlap the short Karoo signature with the much longer and highly resolved marine signature. We simply have no good correlation of these signatures, and this is at least a nice attempt to highlight this ongoing issue.

Whether you can observe a thing or not depends on the theory which you use. (Einstein)

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