Evolution of Mating Systems in the Limnadiid Clam Shrimp

在植物和动物生殖类型的多样性中，一种排列--雄雄异体(雄性和两性的混合体)--以其稀有而独特，仅在18个案例中被发现。这18种中有2种发现在原始甲壳纲支脚类动物中，但另外20种唇足类动物(在Eulimnadia属)的性别比例暗示着雄雄异株。如果这20多个近亲物种真的是雌雄异株的，那么这种罕见的交配系统很可能已经存在于这个血统的祖先中，将雄雄异株的起源放在大约2.8亿年前。这一推断的年龄比理论上预期的要早几个数量级。我们建议结合三个平行的项目(实验室饲养实验、形态比较和DNA测序)来评估雄雄异体是这些甲壳类的祖先特征还是衍生特征。饲养实验将被用来确定这些物种雄雄异株的程度。形态和DNA项目将产生用于估计这些甲壳类物种之间关系的数据。我们将测量每个物种的30个形态特征以及四个DNA区域的序列，这应该能够对这些动物之间的进化关系进行强有力的估计。然后，我们将使用这些估计来确定雄雄异体是否是这些甲壳类动物的祖先条件，如果是真的，这表明这种生殖模式可能已经持续了数亿年，这让人们对雄蕊异体是一种短暂生殖系统的说法产生了怀疑。这项研究项目将实现两个科学目标和三个教育目标。首先，这些数据将使我们能够更好地理解在雌雄同株物种中维持雄性两性的因素，这可以阐明个体之间交配相对于自体受精的重要性。这样的理解可以帮助我们制定更好的驯化动植物管理方法，以及更好的濒危物种保护计划。其次，描绘这一甲壳类群内物种之间的真实关系将有助于确定北美物种的真实数量，这可以用来阐明这些物种中的哪些可能在美国受到威胁或濒危。对于本研究的教育部分，本项目将在三个层面上整合教学和初级研究。首先，资金将直接资助两名研究生和一名本科生，为期三年。其次，这三个PI都将鼓励本科生通过独立研究项目和荣誉论文研究参与研究。第三，这一研究计划的一部分将被纳入阿克伦大学正在进行的两个教育计划：(A)由NSF资助的计划，将基础研究带入A大学生物学入门课程的实验室；以及(B)一个为期5年的私人资助计划，通过辅导计划，让少数族裔高中生在A大学进行基础研究，让本科生和研究生参加一个“研究团队”。在所有研究指导计划中，将优先考虑符合条件的少数民族和女性候选人参加所有级别的活动。

Among the diversity of reproductive types in plants and animals, one permutation - androdioecy (mixtures of males and hermaphrodites) - is distinguished by its rarity, being found in only 18 cases. Two of these 18 species are found in the primitive crustacean class Branchiopoda, but another 20 branchiopod species (in the genus Eulimnadia) have sex ratios suggestive of androdioecy. If these 20+ closely-related species are truly androdioecious, then this rare mating system would likely have been present in the ancestor to this lineage, placing the origin of androdioecy at ~280 million years ago. This inferred age is orders of magnitude older than expected by theory. We propose to combine three parallel projects (laboratory rearing experiments, morphological comparisons, and DNA sequencing) to assess whether androdioecy is an ancestral or derived trait in these crustaceans. The rearing experiments will be used to determine the extent of androdioecy in these species. The morphological and DNA projects will produce data used to estimate the relationships among species within these crustaceans. We will measure 30 morphological characters per species as well as sequence four DNA regions, which should enable a robust estimate of evolutionary relationships among these animals. We will then use these estimates to determine whether androdioecy is an ancestral condition for these crustaceans, which if true, suggests that this reproductive mode may have persisted for hundreds of millions of years, casting doubt on the notion that androdioecy is a transitory reproductive system. This research project will accomplish two scientific and three educational goals. First, these data will allow us to better understand the factors that maintain males with hermaphrodites in androdioecious species, which can shed light on the importance of mating between individuals relative to self-fertilization. Such an understanding can help us to formulate better management practices for both domesticated plants and animals as well better preservation plans for endangered species. Second, delineating the true relationship among the species within this crustacean group will be helpful for determining the true number of species in North America, which can be used to shed light on which of these species may be threatened or endangered in the United States. For the educational components of this research, this project will integrate teaching and primary research on three levels. First, funding will directly support two graduate students and one undergraduate student for three years. Second, all three PI's will encourage undergraduate students to participate in research via independent research projects and honors thesis research. Third, part of this research program will be incorporated into two on-going educational programs at The University of Akron: (a) an NSF-funded program that brings basic research into the laboratories of the Introductory Biology course at U of A, and (b) a 5-year, privately funded program that involves minority high school students in basic research at U of A via a mentoring program, involving both undergraduate and graduate students in a "research team." In all research mentoring programs, priority will be given to qualified minority and women candidates at all levels of participation.