Identifying and Quantifying Disjunctions at Multiple Taxonomic Levels in Western Hemisphere Mammals

I surveyed more than 1,700 Western Hemisphere mammal species ranges to identify, quantify, and examine patterns of disjunction at multiple taxonomic levels. Species that had disjunct populations (isolated by at least 500 km from other parts of the species range) were further analyzed using novel measures of disjunction by determining the distance to the disjunction and the relative area of disjunctions compared to the primary range area. Disjunction at this scale is rare (6.4 percent) in all terrestrial mammals but more common in bats (14.6 percent) than nonvolant mammals. Disjunctions are concentrated in six families, specifically Molossidae (31.5 percent disjunct), Didelphidae (24.7 percent disjunct), Felidae (28.6 percent disjunct), Vespertilionidae (15.3 percent disjunct), Emballonuridae (10.5 percent disjunct), and Phyllostomidae (10.4 percent disjunct). Geographically, 85 percent of disjunct mammal species have ranges that occur entirely or partially in South America. Geographic information systems analysis of species range maps is capable of identifying disjunct species and evaluating the severity of disjunctions. When compiled at the family level, these data suggest that species in certain families are more susceptible to disjunction. In some cases (e.g., species ranges separated by the Amazon rainforest), species-level data offer insight into the causes of disjunction. Study of species identified as disjunct in this study can inform conservation efforts by providing an opportunity to determine the characteristics that enable them to survive as isolated populations.     

对影响逆倾层状边坡稳定性因素的模型试验研究

在工程地质分析的基础上,根据相似理论建立了地质力学模型,研究了逆倾层状边坡岩体的变形破坏机制。介绍了模型试验的设计,并研究了逆倾边坡的稳定性以及岩层的倾角、厚度、结构面的强度对边坡稳定性的影响。结果表明,逆倾层状岩体的变形机制为倾倒变形,破坏模式为弯折破坏;破坏首先在坡顶产生,边坡变形加速的过程是在开挖结束一段时间后才出现;岩层倾角越小,变形加速所持续的时间越长;岩层的厚度和结构面的强度越大变形越小。