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The Phenotypic Plasticity of a South American Lizard

Paper Reviewed
Piantoni, C., Navas, C.A. and Ibargüengoytía, N.R. 2019. A real tale of Godzilla: impact of climate warming on the growth of a lizard. Biological Journal of the Linnean Society 126: 768-782.

In the words of Piantoni et al. (2019), "climatic envelope models have predicted the extinction of populations, but few studies have provided accounts of responses of individual species to climate change." It was therefore their objective to conduct such a study, which they did by examining the spatial and temporal change in growth rates, age at sexual maturity and longevity of two South American lizard populations of Tropidurus torquatus. One of the T. torquatus populations inhabited an urban site that was 1-2°C warmer than, and some 590 km away from, a second population inhabiting a forested site. Growth and reproductive characteristics were measured and analyzed among specimens collected at the two sites, after which they were compared against data obtained from historic specimens collected some five decades earlier that are presently housed in museum collections.

Results of the analysis revealed the following key findings. First, temperatures at both the urban and forested site increased by "~1-2°C over the last four decades." Accompanying this warming, Piantoni et al. report that (1) "data on growth confirmed that contemporary lizards were larger than specimens collected in the 1960s," (2) "lizards collected in the 1960s attained sexual maturity at 5 years of age at the urban site and 6-7 years at the forest site, whereas in 2012 [the] animals achieved the minimum adult size 2 years earlier at both localities," (3) "juveniles grew more slowly and adults lived longer in the forest," (4) "lifespan did not show any temporal variation; therefore, the reproduction period has increased in both populations over the last four decades."

In considering the above response of the two T. torquatus populations to rising temperatures, Piantoni et al. conclude that "Tropidurus torquatus displays morphological and physiological shifts that seem to be mediated by phenotypic plasticity in response to their changing environment." And that is good news to contrast against the model-based predictions of climate-induced animal extinctions. Despite a warming of up to 2°C over the past four decades, two populations of Tropidurus torquatus appear fully capable of adjusting certain growth and reproductive traits to ensure their survivability.

Posted 29 August 2019