Reproductive effort of Plestiodon copei (Squamata, Scincidae), a highland viviparous lizard from Central Mexico

Female reproductive effort is defined as the proportion of total energy or resources devoted to reproduction. In reptiles, there is frequently high inter-and intra-population variation related to several factors, such as food availability, climatic conditions, age and size, all of which, in turn, also influence survival and future reproduction. The present study is the first reproductive effort analysis of a population of the high-mountain scincid lizard Plestiodon copei in central Mexico, focusing on relative litter mass (RLM), investment per capita (INV) and productivity (PROD). We also compared the reproductive efficacy of P. copei to those of other Mexican congeners. We collected 24 gravid females of P. copei over a 4-year period and recorded a total of 90 neonates born in captivity. We found significant variation in neonatal mass amongst individual females and across years. We recorded an average litter size of 3.75 and an average litter mass of 1.25 g, which were positively correlated with both the size and total mass of the reproductive females. The RLM, INV and PROD values (0.301, 0.428 g and 1.236 g x year-1, respectively) for P. copei were greater than those for other Mexican species in the P. brevirostris group (0.290, 0.412 g and 1.135 g x year-1), revealing that females of P. copei from Tenango invest a comparatively high amount of their resources in reproduction.