Morphometric variation in island and mainland populations of two lizard species from the Pacific Coast of Mexico

Uriel Hernández-Salinas,Numa P Pavón,Luis F Rosas Pacheco,Aurelio Ramírez-Bautista

doi:10.1186/s40693-014-0021-3

Abstract

BackgroundBody size exerts a strong influence on the physiology, morphology, ecology, and evolution of other life history traits in vertebrates. We compared the morphometry and allometry of two lizard species (Anolis nebulosus and Aspidoscelis lineattissima) occurring on mainland and island populations on the Pacific Coast of Mexico in order to understand the effect of an insular environment on body size and other morphometric structures.ResultsResults showed that both males and females of A. nebulosus from San Pancho Island were larger in body size than those from the mainland. Moreover, males of A. lineattissima from Cocinas Island exhibited larger forms of most measured morphometric traits than those from the mainland, whereas females from both island and mainland populations did not differ in body size or in other morphometric traits analyzed. Multivariate allometric coefficients of males and females of A. nebulosus from island and mainland populations showed a lower percentage of positive allometries than in A. lineattissima, probably because the former species is highly sedentary. Island populations of both species exhibit male-biased sexual dimorphisms in body size and size-adjusted morphometric traits. In contrast to the mainland population, morphometric comparisons of body size-adjusted traits showed that male A. lineattissima were larger than females only in head length, head width, forearm length, and tibia length, whereas in A. nebulosus, sexual dimorphism was observed just in HL.ConclusionsThis study supports the hypothesis (island rule) that vertebrates on islands are larger than those of conspecifics on the mainland. In addition, sexual dimorphism observed between males and females of both species and populations could be associated with allometric growth (positive or negative) from some morphometric structures, as well as differences in the growth rates of these organisms.

Highlights

Body size exerts a strong influence on the physiology, morphology, ecology, and evolution of other life history traits in vertebrates
In female A. lineattissima, all morphological characteristics were similar between populations (Table 2); males of this species from the island population exhibited larger morphological traits than those from the mainland for all measured morphological characteristics except forearm length (FOL) and tibia length (TL) (Table 2)
principal component analysis (PCA) confirms the pattern observed in the morphometric variation between populations of males and females of A. nebulosus and A. lineattissima (Figures 2 and 3)

Summary

Introduction

Body size exerts a strong influence on the physiology, morphology, ecology, and evolution of other life history traits in vertebrates. Body size is associated allometrically with a variety of reproductive traits (e.g., sexual maturity, egg size, size at hatching, and clutch frequency: Ramírez-Bautista and Vitt 1997; Meiri et al 2012), aspects of sexual selection (sexual dimorphism, territoriality; Anderson and Vitt 1990), niche divergence both between sexes of a single species and across species (Mc Arthur and Levins 1967), and foraging ecology (e.g., active vs ambush foraging; Meiri 2010) Variations in these characteristics have been interpreted as expressions of phenotypic plasticity or reaction norms (Stearns 1992). Interpretations of the functional significance of these population-specific variations facilitated the development of several hypotheses or theories collectively known as the island rule (Foster 1964) This rule predicts that patterns of allometric trajectories or scaling relationships in body proportions of species on islands are different as compared with mainland sites, and this arises due to life in an insular environment relatively poor in competitors and predators (Meiri 2010)

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