Adaptive radiation of land crabs from the Greater Antilles: ecological mechanisms and intraspecific plasticity

适应性辐射往往是物种形成过程中的一个基本步骤。当一个单一的祖先分化成几个具有不同生态适应的谱系时，就会发生这种情况，以利用各种环境。这被认为是发生在陆地殖民牙买加的芝麻蟹，产生了9个目前公认的物种（属Sesarma和Metopaulias）。今天，这些螃蟹可以在岛上各种不同的栖息地找到。虽然最近的一项研究表明，所有的地方性sesarmid物种是单系的，并给出了殖民化和分歧的时间估计，它未能解决牙买加单系内的物种形成事件。因此，在这一点上，没有结论性的信息，实际过程中的适应性辐射可以获得这个有趣的进化情况。目前的项目将侧重于适应性辐射的机制，方法是㈠利用新的分子标记更好地解决牙买加特有蟹种之间的系统发育关系，㈡研究目前导致适应性辐射的过程，重点是种群一级的生态和遗传差异。为了进行比较，将对其他大安的列斯群岛的拟蟹类陆栖蟹动物群进行研究。这一古老的陆地殖民者谱系在生态学和形态学上比牙买加芝麻科分歧更小。我们的研究将揭示是否在Pseudothelphusidae种内可塑性的整体下降可能是过去缺乏适应性辐射的原因。

Adaptive radiation is often a fundamental stepping-stone in the process of speciation. It occurs when a single ancestor diverges into several lineages with different ecological adaptations to exploit a variety of environments. This is assumed to have occurred during the terrestrial colonization of Jamaica by sesarmid crabs, giving rise to nine currently recognized species (genera Sesarma and Metopaulias). Today, these crabs can be found in a variety of different habitats throughout the island. While a recent study showed that all the endemic sesarmid species are monophyletic and gave an estimate for the time of colonization and divergence, it failed to resolve speciation events within the Jamaican monophylum. Therefore, at this point no conclusive information on the actual process of adaptive radiation can be gained out of this interesting evolutionary case. The current project will focus on the mechanisms of adaptive radiation by (i) using new molecular markers to better resolve the phylogenetic relationships among the Jamaican endemic crab species and by (ii) studying current processes leading to adaptive radiation, with the emphasis on ecological and genetic divergence at the population level. For comparison, the pseudothelphusid terrestrial crab fauna of the other Greater Antilles will be studied. This older lineage of land colonisers is ecologically and morphologically less diverged than the Jamaican Sesarmidae. Our study shall reveal whether an overall decreased intraspecific plasticity in the Pseudothelphusidae might be the cause for the lack of adaptive radiations in the past.