Reproductive effort in two viviparous species of blue-tailed skinks (Squamata: Scincidae: Plestiodon) from Mexico

Abstract

The relative allocation of energy organisms devote to reproductive processes (aka reproductive effort) constitutes a central topic in life history theory. We document some aspects of the reproductive ecology and investment of 2 viviparous skinks of the genus Plestiodon from Mexico: an undescribed species previously assigned to P. brevirostris(Plestiodon sp., La Malinche, Tlaxcala, 2,700-3,000 m) and P. dugesii (2 populations, Mazamitla and Tapalpa, Jalisco; 2,400-2,500 m). We used relative litter mass (RLM) as a measure of reproductive effort and calculated a body condition index (BCI) as a proxy of the energy status of non-pregnant females, post-parturient females, and neonates. There were no differences in any of the reproductive characteristics between the 2 populations of P. dugesii. Both species lacked sexual size dimorphism, and female body size did not influence RLM, litter size nor litter mass. However, female BCI influenced RLM and, in P. dugesii, a larger litter size correlated with a lower BCI of neonates. Despite their overall similarities in reproductive investment, there seem to be differential selective pressures shaping offspring characteristics of these 2 lizard species.