RUI: Speciation in the Sea: Developmental Evolution and Host Shifts in the Sacoglossa

为了有效地保护生物多样性，我们必须识别现有物种，并认识到产生物种丰富度的力量。河流和山脉可以将陆地种群分离数百万年，使它们分裂成不同的物种；然而，我们不知道物种是如何在海洋中形成的，因为海洋中几乎没有这样的运动界限。如果一些个体遗传了对新栖息地或食物来源的偏好，或者在一个物种进化出不迁徙的幼虫后，种群的基因变得支离破碎，那么物种形成就会随之而来。为了验证这些想法，我们将构建一个来自全球的草食性海蛞蝓的家谱，通过对它们DNA的系统发育分析来推断物种之间的亲缘关系。对于每个物种，我们将确定作为食物和栖息地的宿主海藻，以及产生的幼虫类型（分散性与非迁移性）。通过建立藻类宿主、幼虫类型和物种之间的关系，我们可以确定哪些特征促成了这一群体的物种形成。如果当蛞蝓转向不同的寄主藻类时形成了新的物种，这将推翻长期以来关于海洋物种形成的假设。这项研究还将测试非迁徙幼虫的进化是否由于母亲的压力而产生更大的后代，以及这些幼虫是否反过来促进了新物种的形成。这些结果将促进我们对为什么某些地区或动物群体比其他地区或动物群体拥有更多物种的理解，并导致许多新的海蛞蝓物种的描述。这两个方面对于保护海洋的生物丰富性都至关重要。

To effectively conserve biodiversity, we must identify existing species and recognize the forces that generate species richness. Rivers and mountains can separate terrestrial populations for millions of years, allowing them to split into distinct species; however, we have little idea how species form in the ocean where there are few such boundaries to movement. Speciation could follow if some individuals inherited a preference for a new habitat or food source, or if populations became genetically fragmented after a species evolved non-migrating larvae. To test these ideas, we will construct a family tree of herbivorous sea slugs from across the globe, inferring relatedness among species by phylogenetic analysis of their DNA. For each species we will determine the host seaweed used as both food and habitat, and the type of larvae produced (dispersing versus non-migratory). By establishing algal hosts, larval types, and relationships among species, we can determine which traits have contributed to speciation in this group. If new species form when slugs switch onto different host algae, this will overturn long-held assumptions about speciation in the sea. This study will also test whether non-migratory larvae evolve due to pressure on mothers to make bigger offspring, and whether such larvae in turn promote the formation of new species. The results will advance our understanding of why certain regions or groups of animals have more species than others, and lead to the description of many new sea slug species. Both aspects are critical to preserving the ocean's biological richness.