Livestock grazing has been demonstrated to affect the population abundance of small rodents in grasslands,but the causative mechanism of grazing on demographic parameters,particularly the age structure and sex ratio,i...Livestock grazing has been demonstrated to affect the population abundance of small rodents in grasslands,but the causative mechanism of grazing on demographic parameters,particularly the age structure and sex ratio,is rarely investigated.In this study,we examined the effects of sheep grazing on the cohort structure and sex ratio of Brandt’s vole(Lasiopodomys brandtii)in Inner Mongolia of China by using large manipulative experimental enclosures during 2010-2013.Our results indicated that sheep grazing significantly decreased the proportion of the spring-born cohort,but increased the proportion of the summer-born cohort.Grazing increased the proportion of males in both spring and summer cohorts.In addition,we found a negative relation between population density and the proportion of the overwinter cohort.Our results suggest that a shift in the cohort structure and the sex ratio may be an important strategy for small rodents to adapt to changes in food resources resulting from livestock grazing.展开更多
Objective:To examine variation in the frequency of arm damage in different sizes of Acanthasterplanci(A.planci),assess how this damage is inflicted by fish predators,and infer the potential role of predation in popula...Objective:To examine variation in the frequency of arm damage in different sizes of Acanthasterplanci(A.planci),assess how this damage is inflicted by fish predators,and infer the potential role of predation in population regulation.Methods:and arm damage frequency and severity was assessed.Frequency of arm damage was compared between sizes.Feeding behavior of fish predators was also observed in the laboratory.Results:This study demonstrates that sublethal predation by triggerfishes on A.planci result inDiameters of A.planci collected from three sites in the Philippines were measured extensive arm damage.Overall,60%of A.planci sampled across all sites had sublethal injuries.The frequency of individuals with missing or regenerating arms was highest in medium-sized young adults(11-20 cm),which coincides with the phase where A.planci shift from cryptic to exposed daytime feeding.Conclusions:The high incidence of arm damage within intermediate-sized sea stars indicates that predators exercise some level of regulation on A.planci populations at a local scale.Identification and protection of putative predators that target the most vulnerable life history stages of A.planci are essential in developing population control strategies and reverse sustained declines in coral cover.展开更多
基金supported by the State Basic Research Program of the Ministry of Science and Technology(2007CB109100)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB11050000).
文摘Livestock grazing has been demonstrated to affect the population abundance of small rodents in grasslands,but the causative mechanism of grazing on demographic parameters,particularly the age structure and sex ratio,is rarely investigated.In this study,we examined the effects of sheep grazing on the cohort structure and sex ratio of Brandt’s vole(Lasiopodomys brandtii)in Inner Mongolia of China by using large manipulative experimental enclosures during 2010-2013.Our results indicated that sheep grazing significantly decreased the proportion of the spring-born cohort,but increased the proportion of the summer-born cohort.Grazing increased the proportion of males in both spring and summer cohorts.In addition,we found a negative relation between population density and the proportion of the overwinter cohort.Our results suggest that a shift in the cohort structure and the sex ratio may be an important strategy for small rodents to adapt to changes in food resources resulting from livestock grazing.
基金Supported by the Department of Sustainability,Environment,Water,Population&Communities-National Environmental Research Program-Tropical Ecosystems Hub.
文摘Objective:To examine variation in the frequency of arm damage in different sizes of Acanthasterplanci(A.planci),assess how this damage is inflicted by fish predators,and infer the potential role of predation in population regulation.Methods:and arm damage frequency and severity was assessed.Frequency of arm damage was compared between sizes.Feeding behavior of fish predators was also observed in the laboratory.Results:This study demonstrates that sublethal predation by triggerfishes on A.planci result inDiameters of A.planci collected from three sites in the Philippines were measured extensive arm damage.Overall,60%of A.planci sampled across all sites had sublethal injuries.The frequency of individuals with missing or regenerating arms was highest in medium-sized young adults(11-20 cm),which coincides with the phase where A.planci shift from cryptic to exposed daytime feeding.Conclusions:The high incidence of arm damage within intermediate-sized sea stars indicates that predators exercise some level of regulation on A.planci populations at a local scale.Identification and protection of putative predators that target the most vulnerable life history stages of A.planci are essential in developing population control strategies and reverse sustained declines in coral cover.
