Geographical variation in reproductive traits and trade-offs between size and number of eggs in the king ratsnake, Elaphe carinata

We collected gravid king ratsnakes (Elaphe carinata) from three geographically separated populations in Chenzhou (CZ), Lishui (LS) and Dinghai (DH) of China to study the geographical variation in female reproductive traits and trade-offs between the size and number of eggs. Not all reproductive traits varied among the three populations. Of the traits examined, five (egg-laying date, post-oviposition body mass, clutch size, egg mass and egg width) differed among the three populations. The egg-laying date, ranging from late June to early August, varied among populations in a geographically continuous trend, with females at the most northern latitude (DH) laying eggs latest, and females at the most southern latitude (CZ) laying eggs earliest. Such a trend was less evident or even absent in the other traits that differed among the three populations. CZ and DH females, although separated by a distance of approximately 1100 km as the crow flies, were similar to each other in most traits examined. LS females were distinguished from CZ and DH females by the fact that they laid a greater number of eggs, but these were smaller. The egg size-number trade-off was evident in each of the three populations and, at a given level of relative fecundity, egg mass was significantly greater in the DH population than in the LS population. (C) 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 701-709.