Examination of the Role of Inbreeding Depression in Maintaining Polymorphism in Eulimnadia texana Packard (Conchostraca, Crustacea)

9628865周进化生物学家试图了解自体受精作为一种可行的生殖形式的情况。通常，与异交后代相比，自交后代的适合度较低。这种“近亲交配衰退”被认为是由隐性有害基因的表达(部分显性模式)或杂合子优势降低(超显性模式)引起的。在前一种情况下，在有规律的近亲繁殖群体中，近亲繁殖衰退应该会减少，而在后一种情况下，只要存在遗传变异，适合度就会随着近亲交配的继续而继续下降。对有规律的自交物种近亲繁殖的长期影响进行量化是区分这两种模式的基础，从而增加对交配系统进化的理解。目前的建议旨在探索在自然自交的对虾物种中维持异交的因素。Eulimnadia Texas ana.通过利用E.Texas ana独特的繁殖系统及其超短的世代时间(5-10天)，我们将研究近亲繁殖在几代自交中的后果。将收集几个健康成分的数据(产蛋量、成熟年龄、存活率和生长)。健康反应将在四个不同近亲交配历史的群体中进行15代的比较。这些适合度数据将被用来比较两个模型对近亲繁殖衰退的预测，从而开始了解在自然种群中维持所观察到的多态的力量。这个项目应该会大大增加我们对植物和动物杂交受精进化的理解。

9628865 WEEKS Evolutionary biologists seek to understand circumstances favoring self-fertilization as a viable form of reproduction. Commonly, offspring produced through self-fertilization have reduced fitness compared to outcrossed counterparts. This "inbreeding depression" is thought to be caused by either expression of recessive deleterious genes (partial dominance model) or by reduced heterozygote advantage (overdominance model). Inbreeding depression should be reduced in a regularly inbreeding population in the former case, whereas fitness continues to decrease with continued inbreeding as long as there is genetic variation in the latter scenario. Quantification of the long-term effects of inbreeding in regularly self-fertilizing species is fundamental to distinguishing between these two models, and thus to increased understanding of mating system evolution. The current proposal is designed to explore factors contributing to the maintenance of outcrossing in a naturally selfing species of shrimp. Eulimnadia texana. By exploiting both E. texana's unique breeding system and its extraordinarily short generation time (5-10 days), the consequences of inbreeding over several generations of self-fertilization will be examined. Data on several fitness components (egg production, age at maturity, survivorship, and growth) will be collected. The fitness responses will be compared for 15 generations in four populations differing in their history of previous inbreeding. These fitness data will be used to compare the predictions of two models for inbreeding depression, and thus to begin to understand the forces contributing to the maintenance of the observed polymorphism in natural populations. This project should lead to a significant increase in our understanding of the evolution of cross fertilization in plants and animals.