The influence of urbanization on morphological traits in the Balsas Basin Whiptail lizard (Aspidoscelis costatus costatus)

Abstract

Urbanization is the process of wildlands transformation for development of human settlements and the resulting ecosystem presents changes that could affect animal populations. Aspidoscelis costatus costatus is an endemic Mexican lizard (Family Teiidae); preliminary observations show possible effects of urbanization on this lizard. We collected 50 A. costatus costatus from an urban area in Ixtapan de la Sal, Estado de Mexico, that were compared with 56 A. costatus costatus from wildlands close to Ixtapan de la Sal and Tonatico, Estado de Mexico. Weight, snout-vent length and other eight morphometric traits, and three meristic traits were recorded for each specimen. We compared between habitat types (urban and wildlands), the differences in morphological variation (dispersion measures), and morphological shifts (central tendency measures) using univariate and multivariate statistical methods. Multivariate results show morphological shifts, but not significant differences in morphological variation. Therefore, there exist no influence of urbanization in the population canalization. In the univariate analyses, four characteristic show differences in dispersion measures using variance-ratio test for normal traits (axilla-groin length and hindlimb length) and Levene’s test for non-normal traits (supraocular scales and femoral pores). Likewise, eight characteristics show differences in central tendency using ANCOVA with snout-vent length as covariate for morphometrics traits (limb measurements, head measurements and axilla-groin length) and Mann-Whitney U test for meristic traits (femoral pores). The differences in some morphometric traits could be explained by the flight requirements of the population in the urbanized habitat; in addition, the differences in femoral pores may be related with chemical pollution.