Why do two sexes of the same species differ in body size holds a long-standing question of evolutionary biology. While many across-species comparisons have focused on ultimate causes behind sexual size dimorphism （SS...Why do two sexes of the same species differ in body size holds a long-standing question of evolutionary biology. While many across-species comparisons have focused on ultimate causes behind sexual size dimorphism （SSD）, only have a few been directed toward elucidating its ontogenetic basis. Urodeles are an amphibian group in which the direction and degree of SSD vary greatly among species. Using demographic data yielded by skeletochronology for 33 urodele species, the current study re- veals a positive across-species correlation between SSD and the sex difference in mean age of adult animals, and the latter in- creases with the corresponding difference in age at maturity; annual growth rate does not differ between the sexes. We conclude that extended longevities in one sex, which is mediated by delayed maturation, would allow it to grow for longer and get larger, with growth rate making a weak contribution to body size. The sex-specific divergence in ontogenetic trajectory might be ex- plained by potentially high growth costs of reproduction to females in association with stronger fecundity selection, and to males that are expected to experience stronger sexual selection [Current Zoology 59 （1）： 142-150, 2013].展开更多
Successful wildlife management must take into account suitable habitat areas. Information on the correlation between distribution ranges and environmental conditions would, therefore, improve the efficacy of in-situ c...Successful wildlife management must take into account suitable habitat areas. Information on the correlation between distribution ranges and environmental conditions would, therefore, improve the efficacy of in-situ conservation of wildlife. In this contribution, correlations between environmental factors and the distribution of 51 amphibians in southern and central China were investigated. Ecological niche factor analysis （ENFA） at a spatial resolution of 1°latitudexllongitude identified a mixture of climatic and habitat factors as important predictors of the occurrence of individual species. The aims of the present work were （i） to evaluate potential distributions of amphibians based on the suitability of areas; （ii） to identify the major environmental descriptors upon which they depend; and （iii） to identify areas of potential high richness that have been overlooked in available inventories. Most of the predicted species ranges of species covered the majority of southern and central China. Six richness hotspots were predicted, of which four have been described previously, but two overlooked （SE Fujian and SE Qinghai）. The prediction model was considered to be relatively accurate and it is recommended that these two new potential hotspots should be subjected to further evaluation and sampling efforts. Amphibians have high ecological preference for high humidity and precipitation, and low annual frost days. ENFA is a useful tool in wildlife conservation assessment because it is able to identify potential hotspots where studies on the correlations between environmental descriptors and the occurrence of particular species could be focused.展开更多
文摘Why do two sexes of the same species differ in body size holds a long-standing question of evolutionary biology. While many across-species comparisons have focused on ultimate causes behind sexual size dimorphism （SSD）, only have a few been directed toward elucidating its ontogenetic basis. Urodeles are an amphibian group in which the direction and degree of SSD vary greatly among species. Using demographic data yielded by skeletochronology for 33 urodele species, the current study re- veals a positive across-species correlation between SSD and the sex difference in mean age of adult animals, and the latter in- creases with the corresponding difference in age at maturity; annual growth rate does not differ between the sexes. We conclude that extended longevities in one sex, which is mediated by delayed maturation, would allow it to grow for longer and get larger, with growth rate making a weak contribution to body size. The sex-specific divergence in ontogenetic trajectory might be ex- plained by potentially high growth costs of reproduction to females in association with stronger fecundity selection, and to males that are expected to experience stronger sexual selection [Current Zoology 59 （1）： 142-150, 2013].
基金partially supported by a University of British Columbia scholarship
文摘Successful wildlife management must take into account suitable habitat areas. Information on the correlation between distribution ranges and environmental conditions would, therefore, improve the efficacy of in-situ conservation of wildlife. In this contribution, correlations between environmental factors and the distribution of 51 amphibians in southern and central China were investigated. Ecological niche factor analysis （ENFA） at a spatial resolution of 1°latitudexllongitude identified a mixture of climatic and habitat factors as important predictors of the occurrence of individual species. The aims of the present work were （i） to evaluate potential distributions of amphibians based on the suitability of areas; （ii） to identify the major environmental descriptors upon which they depend; and （iii） to identify areas of potential high richness that have been overlooked in available inventories. Most of the predicted species ranges of species covered the majority of southern and central China. Six richness hotspots were predicted, of which four have been described previously, but two overlooked （SE Fujian and SE Qinghai）. The prediction model was considered to be relatively accurate and it is recommended that these two new potential hotspots should be subjected to further evaluation and sampling efforts. Amphibians have high ecological preference for high humidity and precipitation, and low annual frost days. ENFA is a useful tool in wildlife conservation assessment because it is able to identify potential hotspots where studies on the correlations between environmental descriptors and the occurrence of particular species could be focused.
