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Geographically Central and Peripheral Populations of Tropical Rainforest Lizards
Moritz, C., Langham, G., Kearney, M., Krockenberger, A., VanDerWal, J. and Williams, S. 2012. Integrating phylogeography and physiology reveals divergence of thermal traits between central and peripheral lineages of tropical rainforest lizards. Philosophical Transactions of the Royal Society B 367: 1680-1687.

The authors note that it is often assumed that large central populations of a species have higher genetic diversity and, therefore, greater potential for adaptive response to environmental change. But they state that "this is not always the case," and that "lineages that have persisted as isolates in peripheral areas through past climate change might well have genotypes that will confer greater resistance to future warming and which could be exploited for genetic translocation," citing the work of Chown et al. (2010).

What was done
Moritz et al. (2012) tested this hypothesis through comparative assays of minimum and maximum critical thermal limits (CTmin and CTmax), as well as optimal performance parameters, including CTopt, across central and peripheral lineages of three species of ground-dwelling skinks (scincid lizards) that are endemic to the rainforests of northeast Australia: Gnypetoscincus queenslandiae, Carlia rubrigularis and Saproscincus basiliscus.

What was learned
In the words of the six scientists, they determined that "peripheral lineages show significantly increased optimal performance temperatures (Topt) relative to central populations, as well as elevated CTmin."

What it means
Moritz et al. state that the peripheral lineages they examined "appear to have evolved higher thermal optima relative to centrally located lineages," noting that this finding "contrasts with the usual assumption that local adaptation of peripheral populations will be overwhelmed by gene flow from the center of the species range or, in the absence of immigration, will experience higher extinction rates," thereby concluding that "long-isolated populations in peripheral rainforests harbor genotypes that confer resilience to future warming."

Chown, S., Hoffmann, A.A., Kristensen, T.N., Angilletta Jr., M.J., Stenseth, N.C. and Pertoldi, C. 2010. Adapting to climate change: a perspective from evolutionary physiology. Climate Research 43: 3-15.

Reviewed 31 October 2012