Skinks Life History Characteristics, Geographic Pattern Of Variation

The Chinese skink (Eumeces chinensis) is a ground-dwelling oviparous sincid lizard that is widely distributed in the southern provinces of China, including Taiwan and Hainan. Skinks collected in April of 2003-2005 from seven geographically separated populations were used to study (1) geographic patterns of variation in life-history traits, (2) the effects of proximate factors on reproductive output, and (3) the effects of incubation temperature on hatchling phenotypes.Most reproducing females were allowed to lay eggs in laboratory enclosures of which each held skinks from the same population, and the remaining females were used to test for the influence of thermal condition and caudal autotomy on the timing of reproduction, reproductive output and egg size. Eggs were incubated under four (three constant and one fluctuating) temperature regimes to assess the effects of incubation temperature on hatching success, incubation length and hatchling phenotypes.Eumeces chinensis is a sexually dimorphic species, with adult males being the larger sex and having larger heads than adult females of the same size in all sampled populations. Although body mass, snout-vent length (SVL) and head size differ significantly among populations, no clear-cut geographic patterns of variation in morphological traits can be detected in this species.Oviposition occurred between mid-May and early July, with females from the low latitudinal (and thus, warm) populations laying eggs earlier than did those from the high latitudinal (and thus, cool) populations. The embryonic stage [Stage 32.8±0.1, 30-35, in the Dufaure and Hubert's (1961) developmental series] at oviposition did not differ among populations.Egg size (clutch mean egg mass), clutch size and clutch mass were positively correlated with female SVL in all populations. Geographic variation in these three traits was very pronounced, with females from the low latitudinal populations laying more but smaller eggs and investing a relatively small amount of resources in single reproductive events than did those from the high latitudinal populations. Geographic variation in egg size, clutch size and clutch mass was still evident even when removing the influence of variation in female size, thus signifying that differences in the involved traits are at least partly determined genetically. SVL-specific egg size...