US-Tanzania Dissertation Enhancement: Diversification in Lake Tanganyika Endemics: Gastropods and Cichlid Fishes Compared

自发现以来，东非裂谷湖的慈鲷动物群作为湖内物种形成和适应分化的显著案例引起了人们的关注。然而，在这些湖泊中，坦噶尼喀湖的独特之处在于它的其他分类群也在一定程度上多样化：在这个湖中发现了350多种独特的非鲷鱼物种。因此，坦噶尼喀是一个独特的生态系统，可以用来研究地方性多样化的过程：为什么在这个单一的湖泊里，一些分类群的多样性如此之大？一种假设是，沿海地区的基质异质性允许分类群在生态上专门针对特定的基质，并且在这种异质性环境中亚种群之间的隔离创造了物种形成的潜力。尽管这一关于湖内异域物种形成的假说在25年前首次提出，但它在东非裂谷湖物种多样性模式的形成中所起的作用在很大程度上尚未得到验证。如果通过底物特异性的种群隔离和栖息地斑块之间有限的分散驱动了多样化，那么假设来自具有高地方性多样性的群体的物种将显示出种群之间受限制的基因流动的证据。这项研究将在坦噶尼喀湖产生大量地方性辐射的两个不相关的群体中调查这一假设：腹足类Lavigeria gastropods和trophiini部落的鲷鱼。研究种类的慈鲷和蜗牛都是底栖食草动物，仅限于岩石基质。这种特定的栖息地关联，再加上它们在湖泊范围内显著的高物种多样性，表明岩石基质上的生态专门化促进了蜗牛和慈鲷类群的物种形成。因此，生态专门化可能推动种群的平行遗传细分和多个不相关分类群体的多样化。为了验证这些假设，将使用线粒体DNA序列和微卫星数据来分析坦桑尼亚基戈马沿岸异质海岸线上的鲷鱼和蜗牛种群遗传结构的比较模式。了解生态专门化对基因流动动态和这些分类群多样性模式的影响，将有助于测试坦噶尼喀湖异常多样化的动物群多样化过程中重要的、长期存在的问题。

Since their discovery, the cichlid fish faunas of the East African rift lakes have drawn attention as remarkable cases of within-lake speciation and adaptive divergence. Among these lakes, however, Lake Tanganyika is distinctive in the extent to which its other taxa have also diversified: over 350 unique non-cichlid species are found within this lake. Tanganyika is therefore a unique ecosystem for studying processes of endemic diversification: how is it that some taxa have diversified so dramatically within this single lake? One hypothesis is that substrate heterogeneity in the littoral zone allows taxa to ecologically specialize on specific substrates, and isolation between subpopulations in this heterogeneous environment creates the potential for speciation. Although this hypothesis for within-lake allopatric speciation was first proposed over 25 years ago, its role in creating patterns of species diversity within the East African rift lakes remains largely untested. If isolation of populations through substrate specificity and limited dispersal among habitat patches has driven diversification, it is hypothesized that species from groups with high endemic diversity will show evidence of restricted gene flow between populations. This research will investigate this hypothesis in two unrelated groups that have produced substantial endemic radiations in Lake Tanganyika: Lavigeria gastropods, and cichlid fishes of the tribe Tropheini. Study species of cichlid fishes and snails are all benthic herbivores restricted to rocky substrates. This obligate habitat association, coupled with their notably high lake-wide species diversity, suggests that ecological specialization on rocky substrate has promoted speciation in both snail and cichlid groups. Therefore, ecological specialization may drive parallel genetic subdivision of populations and diversification in multiple unrelated taxonomic groups. To test these hypotheses, both mitochondrial DNA sequence and microsatellite data will be used to analyze comparative patterns of population genetic structuring in cichlids and snails along the heterogeneous shoreline bordering Kigoma, Tanzania. Understanding the impact that ecological specialization has on gene flow dynamics and patterns of diversity across these taxa will allow the testing of important, long-standing questions about the processes of diversification among Lake Tanganyika's exceptionally diverse faunas.