Evolutionary Analysis of the Generation and Loss of Biodiversity

我们正在进行一项大型研究的一部分，该研究考察了物种占据生态和地理范围的动态性质。最终目标是确定进化史是否以及如何决定了物种范围的大小，从而决定了它对灭绝的脆弱性。研究的重点是夏威夷群岛特有的大型和多样化的蜘蛛物种辐射。目前的研究目标是：(1)解决4类蜘蛛之间的进化关系，其中两类蜘蛛在岛屿内广泛分化，其他蜘蛛主要在岛屿或山脉之间分化；(2)对于单个种群，估算每个物种种群之间的有效种群大小和基因流动（使用分子标记）。如果有可能通过物种的进化史来确定物种之间分布的自然进化变化，那么就有可能区分那些自然受到限制的物种和那些由于人类影响而受到限制的物种。拟议研究的目的是了解种群和物种之间的关系，以便我们能够继续测试一个物种的自然进化未来是否可以预测。我们认为，对于以广泛迁移为特征的物种，种群的局部细分是不可能的。因此，物种分化只可能发生在一个种群被隔离的时候，例如当它到达一个新的陆地时，这时新物种也可能在数量和范围上扩大。在这种情况下，一个物种群体中最近形成的代表将是最广泛的，而该谱系中较老的物种将受到更多限制，容易灭绝。对于迁移减少的物种，局部种群细分应该是可能的，细分的物种在丰度和范围上受到更大的限制。在第二种情况下，最近衍生的物种应该是最受限制和最容易自然灭绝的。本研究中产生的数据将表明，如何将进化支之间的系统发育关系信息与有效种群大小和种群之间的基因流动数据最有效地结合起来，以便对分布变化的显著模式进行统计测试。

Gillespie 9726573 We are undertaking part of a large study examining the dynamic nature of ecological and geographic range occupation by species. The ultimate goal is to determine whether, and how, evolutionary history dictates the size of a species range, and hence its vulnerability to extinction. The focus of the research is a large and diverse species radiation of spiders endemic to the Hawaiian Islands. The current objectives are: (1) to resolve the evolutionary relationships among 4 groups of the spiders, two of which differentiate extensively within islands, while the others differentiate primarily between islands or mountains; and (2) for a single group, to generate estimates of effective population size and gene flow (using molecular markers) between populations of each species. If it were possible to determine the natural evolutionary changes in distribution among species through their evolutionary history, then it may be possible to distinguish species that are naturally restricted in their range from those that have been confined due to human impact. The objective of the proposed study is to understand relationships among populations and species, so that we will be able to go on to test whether the natural evolutionary future of a species can be predicted. We have argued that, for species characterized by extensive migration, local subdivision of populations will be impossible. Therefore, species divergence can only occur when a population becomes isolated, for example when it reaches a new land mass, at which time the new species is also likely to expand in abundance and range. In such a scenario, the most recently formed representative of a species group will be the most widespread, while the older species in that lineage will be more restricted and vulnerable to extinction. For species exhibiting reduced migration, local population subdivision should be possible, with subdivided species becoming more restricted in abundance and range. In this second scenario the more recently derived species should be the most restricted and vulnerable to natural extinction. The data generated in this study will indicate how information on phylogenetic relationships among clades can be most effectively coupled with data on effective population size and gene flow between populations in order to statistically test for significant patterns of distributional change.