Fluctuating asymmetry as a tool for assessing development stability on small mammals from the Argentine agroecosystem

Abstract

Evolutionary biologists have not paid as extensive attention to nongenetic compo-nents of variation as they have done to genetic variation of phenotypic traits. Gen-erally, nongenetic components are grouped in categories such as the "environmental variation". However, they differ in both their origin and biological significance.Individuals experience different environmental conditions resulting in phenotypicplasticity. Therefore, it is necessary to consider the developmental system and howit produces variation in phenotypic traits. Developmental instability (DI) resultsfrom random variation during development, which produces deviations in each de-veloping structure from expected for both genotype and environment. Fluctuatingasymmetry (FA), defined as small random deviations of perfect bilateral symme-try, has been suggested as a good DI estimator. Recently, agricultural activity hasincreased, being one of the key causes of habitat destruction and subsequent bio-diversity loss. Thus, we evaluated the effect of agricultural intensification throughlocal and landscape variables on DI (skulls and mandibles) of individuals of threerodent species. Landscape variables were recorded: area perimeter ratio (PA) andhabitat diversity index. The local variable was vegetation volume (Vv) of habitatedge. We used individuals housed in the UNRC-Mammal Collection caught dur-ing 2016 in the central-Argentine agroecosystem. Type I and II landmarks weredigitized in 2D images. Asymmetric components (size and shape) were extractedusing geometric morphometrics. For the analysis, GLM were generated, using theAIC-Criterion to select them. No associations between explanatory variables andFA were found in Akodon azarae and Calomys musculinus skulls. A negative asso-ciation of FA with PA and Vv was observed in C. venustus skull. No associationswith the explanatory variables were found for any of the species? mandibles. Thestudy shows a disparity in morphological responses, depending on whether the skullor the mandible is analyzed. The results are discussed based on the degree of habitatrequirements of the species.