Maternal and environmental influences on reproductive success of a viviparous grassland lizard

Understanding the factors that drive population persistence and growth is fundamental to both conservation management and evolutionary biology. Internal (maternal) and external (environmental) factors can affect female reproductive output, and in oviparous reptiles both may strongly influence offspring phenotype and quality. However, the link between these effects, their importance for reproductive output and offspring characteristics of live-bearing lizards, and whether population declines are linked to these factors in modified versus native habitats are unknown. We used a common New Zealand skink species, Oligosoma maccanni (McCann’s skink), found in grazed native and exotic grassland to test whether differences in environmental or maternal characteristics influenced birth date, pregnancy success and offspring phenotype. In both grassland types the date of birth was c. 8 days earlier at lower altitudes (altitudinal range = 564–719 m a.s.l), and small females were less likely to have successful pregnancies. However, larger females had more weak or deformed offspring, suggesting that reproductive senescence may exist in this species. While other research shows that exotic grasslands do not support as many skinks as native tussock grassland, reproductive success of pregnant skinks (viable litter size) was not affected by habitat modification. However, neonates had greater body condition (mass for length) when from females with higher post-partum body condition, and these females were from the native tussock grasslands. In conjunction with previously published data on McCann’s skink, our data suggest that reduced offspring quality may contribute to the lower population numbers in the exotic habitats.