Linking environmental factors, life history and population density in the endangered freshwater snail Margarya melanioides (Viviparidae) in Lake Dianchi, China

摘要: Understanding how environmental changes affect life-history traits is important for predicting population dynamics of a species. As one the most pervasive forms in freshwater systems, eutrophication can change animals through density-dependent/independent processes. However, empirical evidence remains scarce regarding mechanisms by which influences traits. We conducted field study linking eutrophication, and density Margarya melanioides Lake Dianchi, largest lake Yun-Gui plateau China eutrophicated humans, over 14 months 2009-2010. estimated key (growth reproduction) M. Then, comparing some with those recorded 1931-1933 (when extent was comparatively low), we found that this snail had increased its fecundity (from 1.07 to 4.24 offspring/brood-bearing female) proportion females broods (23.6 77.4%), decreased body size (54.2 47.6 mm) threshold reproduction (46 35 mm), distorted female/male sex ratio (1.6:1 0.97:1). These findings suggest has adapted response intensified eutrophication. A structural equation model indicated influenced two related but opposing pathways: primarily decreasing reduce secondarily directly promoting reproduction. Our results not only support significance determination animals, also density-dependent effects on may be stronger than direct when small.