Proximate mechanisms that contribute to female-biased sexual size dimorphism in an anguid lizard

Abstract

Various proximate mechanisms have been proposed to explain sexual size dimorphism (SSD) in vertebrates. Identifying the proximate causation of SSD allows insight into the ultimate reasons why SSD exists. I explored whether differential growth rates and (or) mortality explain SSD in the lizard Elgaria coerulea (Baird and Girard, 1852). I estimated growth parameters for males and females using the logistic-by-weight growth curves and determined survivorship using two complimentary methods: standard life-table calculations and capture–recapture methods. The former calculated age-specific survivorship, whereas the latter tested for differences in survivorship between males and females while considering differences in their recapture rates. I considered age-specific SSD as further evidence of SSD independent of differential mortality. Differences in growth asymptote, not intrinsic growth rate, contribute to SSD in this population. SSD is not due to differential mortality, as there is no difference in survivorship of males and females over 3 years of age. In addition, there is age-specific SSD with females larger than males for individuals 4 years of age and greater. The female-biased SSD may be a result of selection for large body size, although further studies are necessary to identify the ultimate cause of SSD in this species.

Sex size and shape differences in the lacertid community (Podarcisspp. andArchaeolacertasp.) from the Lake Skadar region (Montenegro)

“…Different patterns of genetic correlations between sexes, allometry and phylogenetic effects could underly the observed differences at the species level (e.g. Hedrick & Temeles 1989;Butler & Losos 2002;Rutherford 2004). Numerous local factors related to specific microhabitat, or those related to population history including founder effect, past variation in population size and behavior could produce such variation (Badyaev & Hill 2000) between populations.…”

“…Olsson et al 2002;Rutherford 2004). Consequently, similar patterns of body size and shape differences between the sexes (larger overall body size and relative head size in males and larger relative trunk length in females) are observed in many lizard taxa (e.g.…”

Ontogeny of a sexual dimorphism in tiger salamanders

“…Often trait divergence occurs at or just after sexual maturation (Kratochvíl et al 2003;Rutherford 2004). In some cases, however, sexual differentiation may begin at the earliest stage of development (King et al 1999;Olsson et al 2002) or well before sexual maturation (Haenel and John-Alder 2002).…”

Size dimorphism in Rankinia [Tympanocryptis] diemensis (Family Agamidae): sex-specific patterns and geographic variation

“…SSD in adults results from differential physiological, behavioural, and ecological processes occurring during some stage of development (Badyaev, 2002; Rutherford, 2004; Le Galliard et al. , 2006).…”

“…Body size bias between the sexes, sexual size dimorphism (SSD), is a widespread phenomenon occurring in a variety of taxa (Andrews & Stamps, 1994;Butler, Schoener & Losos, 2000;Schulte-Hostedde, Millar & Gibbs, 2002;Lindenfors, Székely & Reynolds, 2003;Fox & Czesak, 2006). The function and evolution of SSD can be explained by two major hypotheses: sexual selection typically acting to increase male size (intrasexual selection hypothesis) and natural selection for increased female size (fecundity advantage hypothesis) (Blanckenhorn, 2000;Storz et al, 2001;Cox, Skelly & John-Alder, 2003;Rutherford, 2004). Another hypothesis, involving sex-specific niche divergence, is also thought to play a large role in the evolution of SSD (Temeles et al, 2000).…”