Abstract
BackgroundEnvironmental variation associated with season length is likely to promote differentiation in life-history traits, but has been little studied in natural populations of ectotherms. We investigated patterns of variation in egg size, clutch size, age at sexual maturity, maximum age, mean age, growth rate and adult body size in relation to growth season length among 17 populations of Andrew’s toad (Bufo andrewsi) at different latitudes and altitudes in the Hengduan Mountains, western China.ResultsWe found that egg size, age at sexual maturity, and mean age increased with decreasing length of the growth season, whereas clutch size showed a converse cline. Body size did not increase with decreasing length of the growth season, but was tightly linked to lifetime activity (i.e. the estimated number of active days during lifetime). Males and females differed in their patterns of geographic variation in growth rates, which may be the result of forces shaping the trade-off between growth and reproduction in different environments.ConclusionsOur findings suggest that growth season plays an important role in shaping variation in life-history traits in B. andrewsi across geographical gradients.Electronic supplementary materialThe online version of this article (doi:10.1186/s12983-016-0138-0) contains supplementary material, which is available to authorized users.
Highlights
Environmental variation associated with season length is likely to promote differentiation in lifehistory traits, but has been little studied in natural populations of ectotherms
We investigated how egg size, clutch size, age at maturity, mean age, maximum age and growth rates in males and females vary with variation in the length of the growth season for both sexes
Egg size and clutch size The Generalized Linear Mixed Models (GLMMs) revealed that average egg size was significantly predicted by the length of the growth season (F1,3.852 = 4.474, P < 0.01), and not predicted by latitude, altitude and female body size (Table 1, Fig. 2a)
Summary
Environmental variation associated with season length is likely to promote differentiation in lifehistory traits, but has been little studied in natural populations of ectotherms. Time constraints associated with the length of the activity season may play an important role in shaping allocation patterns between investment into growth and longevity [26, 29]. Shorter growth seasons should increase the time taken to reach adulthood, leading to a higher age at maturation [8, 30]. This is for example observed in reptiles, for which longevity often increases with decreasing growth season [7, 31, 32]
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