Dissertation Research: Patterns of Reproductive Isolation in the Brachionus plicatilis Species Complex (Rotifera)

大米指定涉及一个种群的分裂，这样一个新种群的成员不能与另一个群体的成员交配并产生可生育的后代。在几乎所有的情况下，对于这种生殖隔离到底是什么生物变化造成的，人们知之甚少。这项拟议的研究将使用褶皱臂尾轮虫来解决这个问题，这种轮虫的种群生活在世界各地的盐湖和沿海池塘，并表现出一系列的杂交能力。首先，将对褶皱假单胞菌的两个基因进行测序，以确定不同种群之间的遗传差异和进化关系(即，家谱)。其次，不同种群的代表将被杂交，杂交后代的命运将被密切关注。将讨论以下具体问题：首先出现哪些导致生殖隔离的性状差异(即，是什么启动了物种形成，又是什么完成了物种形成)？是什么进化过程导致了它们的分化？一个新物种起源的速度有多快？了解生殖隔离进化的生物学基础，对于全面理解产生生物多样性的过程至关重要。此外，包括轮虫在内的许多生物群都有“隐藏的”物种，即在生殖上完全隔离但看起来不明显的种群，因此在大多数调查中不被认为是不同的物种。除了确定目前被归类为“褶皱臂尾轮虫”的物种的真实数量外，这项研究还将提供对隐藏物种产生的机制以及它们的常见程度的洞察，了解这些机制对于准确评估生物多样性至关重要。

0105040RiceSpeciation involves the splitting of a population, such that the members of either of the new populations are unable to mate and produce fertile offspring with the members of the other. In nearly all cases, little is known about exactly what biological changes are responsible for this reproductive isolation. The proposed research will address this question using the rotifer Brachionus plicatilis, populations of which inhabit salt lakes and coastal ponds worldwide and exhibit a range of abilities to interbreed. First, two genes from B. plicatilis will be sequenced to determine genetic divergences and the evolutionary relationships (i.e., a family tree) between different populations. Second, representatives of different populations will be crossed and the fate of the hybrids followed closely. The following specific questions will be addressed: What trait differences causing reproductive isolation arise first (i.e., what initiates speciation, and what finalizes it)? What evolutionary processes are responsible for their divergence? How rapidly can and does a new species originate?Understanding the biology underlying the evolution of reproductive isolation is critical to a general understanding of the processes responsible for producing biological diversity. Furthermore, many groups of organisms, including rotifers, have "hidden" species, populations that are fully reproductively isolated but do not look distinct and are thus not recognized as distinct species in most surveys. In addition to determining the true number of species currently lumped together as "Brachionus plicatilis", this study will provide insight into the mechanisms by which hidden species arise and how common they are, an understanding of which is essential to any accurate assessment of biodiversity.