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

[105040]水稻分化涉及到种群的分裂，这样新种群中的任何一个成员都不能与另一个成员交配并产生可育的后代。在几乎所有的情况下，人们对究竟是什么生物变化导致了这种生殖隔离知之甚少。拟议的研究将使用轮虫Brachionus plicatilis来解决这个问题，这些轮虫居住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，研究人员将对两个基因进行测序，以确定不同种群之间的遗传差异和进化关系（即家谱）。其次，不同种群的代表将进行杂交，杂交后代的命运将密切关注。以下具体问题将被解决：导致生殖隔离的性状差异首先出现（即，是什么启动了物种形成，又是什么结束了物种形成）？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？了解生殖隔离进化背后的生物学，对于全面了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体都有“隐藏”的物种，这些种群在繁殖上完全隔离，但看起来并不明显，因此在大多数调查中不被认为是独特的物种。除了确定目前集中在一起的“弯曲臂尾轮虫”物种的真实数量外，这项研究还将深入了解隐藏物种产生的机制以及它们的普遍程度，这对任何准确评估生物多样性都是至关重要的。

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.