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Environmental pressures vary by geographic location and will lead to differentiation in life history traits according to which maximize fitness. Life history theory predicts that harsh environments are likely to select for larger egg or offspring size, and for a stronger trade-off between offspring size and number. To test this prediction, we compared life history traits among 11 plateau brown frog (Rana kukunoris) populations at different altitudes. We found that females with a concomitant increase in body size produce larger eggs and more offspring in warm environments than females in cold environments do. Moreover, females from two natural populations produced offspring of different sizes between years. The decreasing resource allocation to current offspring size and number may increase survival and future fecundity in harsh environments. Thus, there may be a trade-off between mortality and fecundity in different environments. In addition to body size, we suggest that temperature plays an important role in shaping maternal investment variation in R. kukunoris across geographical gradients. [ABSTRACT FROM AUTHOR]

Body size is expected to affect the mating behaviour and mating patterns of simultaneous hermaphrodites, because it can influence fecundity, mate choice and mechanical constraints to mating. However, there is a lack of detailed research on size-dependent mating patterns in hermaphroditic species, including aquatic pulmonates. We investigated mating patterns and mating success in the simultaneous hermaphroditic pond snail Radix lagotis (Gastropoda: Pulmonata). We found that fecundity increased with body size and we observed a strong pattern of size-assortative mating across two breeding seasons. Sperm donors were more likely to inseminate large snails than small snails, and pairings between two large individuals were more likely to result in successful copulations than pairings of two small individuals or two individuals of differing sizes. Other possible explanations (mechanical constraint) for these patterns are also discussed. [ABSTRACT FROM AUTHOR]