Monday, March 11, 2013

Lizards, temperatures & the future

Sonoran Spiny-tailed Iguana, Ctenosaura macrolopha, juvenile. JCM 

Two papers published early on-line suggest lizards are facing a difficult future due to climate change. Both papers examine the role of temperature on lizard life history. Grigg and Buckley (2013) phylogeny and geography constrain thermal tolerances of lizards similarly within continents, but they are variably within clades. Conservative nature  of thermal tolerances across lineages suggests that the potential for local adaptation to alleviate the impacts of climate change on lizards is most likely limited.

A second study by Meiri et al (2013) used a data set that included 861 lizard species and looked at the relationship between lizard body temperature and environmental temperature. They tested for the influence of both body and environmental temperatures on ecological and life-history traits while considering the influence of common ancestry.

Meiri et al found body temperatures and mean annual temperatures are uncorrelated. However, when they considered: activity time (nocturnal species have low body temperatures), use of space (fossorial and semi-aquatic species are ‘colder’), insularity (mainland species are ‘hotter’) and phylogeny, the two temperatures are positively correlated. High body temperatures are only associated with larger hatchlings and increased rates of biomass production. They also found annual temperatures are positively correlated with clutch frequency and annual longevity, and negatively correlated with clutch size, age at first reproduction and longevity.

Therefore, they conclude that species with low body temperatures do not seem to have ‘slower’ life-history attributes than species with high body temperatures. The longer seasons prevalent in warm regions, and physiological processes that operate while lizards are inactive (but warm enough), make environmental temperatures better predictors of lizard life-history variation than body temperatures. This surprisingly greater effect of environmental temperatures on lizard life histories hints that global warming may have a profound influence on lizard ecology and evolution.

Citations
Grigg J. W. and L. B. Buckley. 2013.Conservatism of lizard thermal tolerances and body temperatures across evolutionary history and geography. Biology Letters (2) doi: 10.1098/rsbl.2012.1056.

Meiri, S., Bauer, A. M., Chirio, L., Colli, G. R., Das, I., Doan, T. M., Feldman, A., Herrera, F.-C., Novosolov, M., Pafilis, P., Pincheira-Donoso, D., Powney, G., Torres-Carvajal, O., Uetz, P. and Van Damme, R. (2013), Are lizards feeling the heat? A tale of ecology and evolution under two temperatures. Global Ecology and Biogeography. doi: 10.1111/geb.12053

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