IRFP: Testing Hypotheses Regarding Function and Evolution of Placentotrophy, Using Viviparous Skinks as a Model

国际研究奖学金项目使美国科学家和工程师能够在国外进行9至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持James U. Van Dyke博士与Michael Thompson博士在澳大利亚悉尼大学进行为期24个月的研究。生殖分配机制是动物个体向其后代提供资源的手段。这些机制可能通过改变生殖产出、亲本生存或两者的变化来应对食物网的破坏和随后的资源限制。因此，了解生殖分配机制对于理解全球环境变化背景下的种群动态至关重要。在羊膜动物中，胎盘营养蜥蜴科是唯一表现出完全依赖蛋黄（卵磷脂）和完全依赖胎盘（胎盘）之间的中间类型。因此，它们长期以来一直是羊膜胎盘进化研究的唯一可用模型。然而，直到最近，我们对胎盘形态和功能多样性的理解才进展到有关羊膜胎盘保护进化的问题可以得到解决。本研究在了解羊膜胎盘功能和进化方面取得了两大进展。首先，它分析了在食物限制期间对蛋黄（卵黄）和胎盘（胎盘）的中间依赖如何影响生殖成功。其次，它利用一种新的示踪技术来确定哪些胎盘组织负责提供胎盘营养石龙子的胚胎营养。总之，这个项目的结果为利用卵黄和胎盘的物种的胎盘功能提供了新的见解，这促进了对胎盘从脊椎动物祖先的卵黄和胎盘营养状态进化的理解。通过关注生殖对食物限制的反应，本研究还为机械预测人口水平对全球环境变化的反应提供了模板。因此，本研究直接将胎盘功能研究与面对全球环境变化的保护联系起来。

The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four-month research fellowship by Dr. James U. Van Dyke to work with Dr. Michael Thompson at the University of Sydney, in Sydney, Australia. Mechanisms of reproductive allocation are the means by which individual animals provision resources to their offspring. These mechanisms may respond to food web disruption and subsequent resource limitation via alterations of either reproductive output, parental survival, or both. Therefore, understanding mechanisms of reproductive allocation is central to understanding population dynamics within the context of global environmental change. Among amniotes, placentotrophic lizards of the family Scincidae are the only taxa to exhibit intermediacy between complete reliance on yolk (lecithotrophy), and complete reliance on placentation (placentotrophy), for embryonic nutrition. As a result, they have long served as the only available models for studies of evolution of placentation in amniotes. However, only recently has our understanding of the diversity of placental morphology and function progressed to the point that questions regarding the evolution of amniote placentotrophy can be addressed. This research makes two major advances to the understanding of amniote placental function and evolution. First, it provides an analysis of how intermediate reliance on both yolk (lecithotrophy) and placenta (placentotrophy) affect reproductive success during periods of food limitation. Second, it utilizes a novel tracer technique to determine which placental tissues are responsible for providing embryonic nutrition in placentotrophic skinks. Together, the results of this project provide novel insights into the placental function of a species that utilizes both lecithotrophy (yolk) and placentotrophy (placenta), which advances understanding of the evolution of placentotrophy from an ancestral lecithotrophic state in vertebrates. By focusing on reproductive responses to food limitation, this research also provides a template for mechanistically predicting population-level responses to global environmental change. Therefore this research directly links studies of placental function with conservation in the face of global environmental change.