Morphological variation in the Cape Dwarf Chameleon (Bradypodion pumilum) as a consequence of spatially explicit habitat structure differences

Abstract

An organism's phenotype is to some extent influenced by costs and benefits in terms of natural and sexual selection. The intensity of natural selection can in part be driven by habitat structure, which may result in varying levels of crypsis and/or selection on traits related to maximizing performance in that habitat. This may be countered by sexual selection, which can lead to sexual dimorphism in body size and/or the expression of conspicuous ornamentation relating to maximizing reproductive success. The intensity of these forces can also be different between the sexes, resulting in complex patterns of phenotypic variation. With this in mind, we examined morphological variation within the Cape Dwarf Chameleon, Bradypodion pumilum. The species inhabits two geographically disjunct habitat types and, in the present study, we demonstrate that chameleons from the two habitats show morphological differences. Large, conspicuous individuals inhabit closed vegetation, whereas small, drab individuals inhabit open vegetation. However, when morphological traits are size-adjusted, the open vegetation morph displays many traits that are larger for its body size than the closed vegetation morph, especially for characters related to locomotion (limbs) and bite force (head width). Sexual dimorphism is also present, although the degree and number of dimorphic characters was very different between the two morphs, with size-adjusted male-biased dimorphism much more pronounced in the closed morph. Overall, our findings suggest that natural selection in open habitats limits both body size and conspicuous characters, although sexual selection in closed habitats favours the development of ornamentation related to display.

Taxonomic adjustments in the systematics of the southern African lacertid lizards (Sauria: Lacertidae)

“…Morphological traits can be labile, and the phenotype may be influenced by factors such as microhabitat and environment (e.g. Vanhooydonck & Van Damme 1999;Herrel et al 2002;Revell et al 2007;Barros et al 2011;Hopkins & Tolley 2011;Edwards et al 2012;Herrel et al 2013), dietary preferences (e.g. Measey et al 2009), sexual selective pressures , or a combination of these factors.…”

Ancient forest fragmentation or recent radiation? Testing refugial speciation models in chameleons within an African biodiversity hotspot

“…, 2006, 2008, 2010; Measey et al. , 2009; Hopkins & Tolley, 2011), and in East Africa, a species‐rich genus of chameleon ( Kinyongia ; Tilbury et al. , 2006) is strongly associated with forested habitat (Tilbury et al.…”

Convergent Evolution Associated with Habitat Decouples Phenotype from Phylogeny in a Clade of Lizards

“…For example, rock-dwelling species typically have flat heads and bodies that allow them to fit into narrow cracks, yet long forelimbs adapted for climbing [8], [16]. In contrast, some arboreal species that specialize on narrow substrates have short limbs and narrow, tall bodies [17]–[20].…”