The Evolution of Placentas in the Poeciliid Fishes: An Empirical Study of the Evolution of Complexity

鱼类胎盘的进化：复杂性进化的实验研究胎盘是一个复杂的器官，它是许多适应性的复合体，必须很好地整合才能发挥正常的功能。David Reznick和Michael Ghedotti将研究Poeciliidae鱼科中胎盘的进化。他们将根据DNA序列和形态建立一棵“家谱”，以确定胎盘是否在不同的分支上独立进化，并确定有或没有胎盘的物种组。对30种亲缘关系密切、具有不同母体供养形式的鱼类进行的实验，将检验最近一项关于胎盘进化理论的预测。生物学家们将共同努力，提供见解来完善理论，而理论家们将提供见解，提出新的实验研究路线。在《物种起源》中，达尔文有一章名为《理论上的困难》，考虑了自然选择对进化论最严重的挑战。其一是复杂器官的起源：进化似乎不太可能同时整合许多特征。他提出，如果每一步都代表一种适应，复杂性可以通过小步进化。这些鱼为检验达尔文的命题提供了机会。这项研究还将为学生提供多学科培训，涉及生物学的几个领域，并提供一个进化论的案例研究。

David Reznick + Michael Ghedotti DEB-0416085 + 0415633 AbstractThe Evolution of Placentas in the Poeciliid Fishes: An Empirical Study of the Evolution of ComplexityThe placenta is a complex organ that is a composite of many adaptations that must be well integrated for proper function. David Reznick and Michael Ghedotti will study the evolution of the placenta in the fish family Poeciliidae. They will develop a "family tree", based on DNA sequence and morphology, to determine if the placenta evolved independently on different branches and to define groups of species that do or do not have the placenta. Experiments on 30 species of those fish that are closely related and have different forms of maternal provisioning will test the predictions of a recent theory for the evolution of the placenta. Working together, the biologists will provide insights to refine the theory, while theoreticians will provide insights to suggest new lines of experimental inquiry.In the Origin of Species, Darwin included a chapter entitled "Difficulties on Theory", considering the most serious challenges to the theory of evolution by natural selection. One was the origin of complex organs: it seemed improbable that evolution could integrate many traits at once. He proposed that complexity could evolve by small steps if each represented an adaptation. These fish provide an opportunity to test Darwin's proposition. The research will also offer multidisciplinary training for students, be relevant to several fields of biology, and present a case study in evolution.