Saturday, November 24, 2012

Squamate Body Elongation & Climate

Gymnopthalmus underwoodi, a species not included in this study.

The evolution of elongated body shapes in squamate vertebrates has intrigued biologists for decades. Grizante et al. (2012) suggest several factors may explain how the environment influences the evolution of body elongation, and note climate needs to be incorporated in this scenario to evaluate how it contributes to morphological evolution. Climatic parameters include temperature and precipitation, two variables that likely influence environmental characteristics, including soil texture and substrate coverage, which may define the selective pressures acting during the evolution of morphology. GIS (geographic information system) techniques are now available and can now be included in evolutionary biology studies. Grizante et al used GIS in present study to test for associations between variation in body shape and climate in the tropical lizard family Gymnophthalmidae. They first investigated how the morphological traits that define body shape are correlated in these lizards and then tested for associations between a descriptor of body elongation and climate. Their analyses revealed that the evolution of body elongation in Gymnophthalmidae involved concomitant changes in different morphological traits: trunk elongation was coupled with limb shortening and a reduction in body diameter, and the gradual variation along this axis was illustrated by less-elongated morphologies exhibiting shorter trunks and longer limbs. The variation identified in Gymnophthalmidae body shape was associated with climate, with the species from more arid environments usually being more elongated. Aridity is associated with high temperatures and low precipitation, which affect additional environmental features, including the habitat structure. This feature may influence the evolution of body shape because contrasting environments likely impose distinct demands for organismal performance in several activities, such as locomotion and thermoregulation. The authors establishes a connection between morphology and a broader natural component, climate, and introduces new questions about the spatial distribution of morphological variation among squamates.

Grizante MB, Brandt R, Kohlsdorf T (2012) Evolution of Body Elongation in Gymnophthalmid Lizards: Relationships with Climate. PLoS ONE 7(11): e49772. doi:10.1371/journal.pone.0049772

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