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

国际研究奖学金计划使美国科学家和工程师能够在国外进行9到24个月的研究。该项目的奖项提供了联合研究的机会，并提供了使用国外独特或互补的设施、专业知识和实验条件的机会。该奖项将资助詹姆斯·U·范·戴克博士与澳大利亚悉尼大学迈克尔·汤普森博士合作的为期24个月的研究奖学金。生殖分配机制是个体动物向其后代提供资源的手段。这些机制可能通过改变生殖产量或亲本存活率，或两者兼而有之，对食物网的破坏和随后的资源限制做出反应。因此，了解生殖分配机制对于理解全球环境变化背景下的人口动态至关重要。在羊膜动物中，在完全依赖卵黄(卵磷脂营养)和完全依赖胎盘(胎盘营养)获得胚胎营养之间，Scinsidae科的胎盘营养性蜥蜴是唯一的类群。因此，它们长期以来一直是研究羊膜胎盘形成进化的唯一可用的模型。然而，直到最近，我们对胎盘形态和功能的多样性的了解才有了进展，关于羊膜胎盘营养进化的问题才得以解决。这项研究在理解羊水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时期，对卵黄(卵磷脂营养)和胎盘(胎盘营养)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在胎盘营养性骨节中提供胚胎营养。总之，该项目的结果为同时利用卵黄和胎盘营养的物种的胎盘功能提供了新的见解，这促进了对脊椎动物胎盘营养从祖先的卵磷脂营养状态进化的理解。通过专注于对食物限制的生殖反应，这项研究还为机械地预测人口水平对全球环境变化的反应提供了一个模板。因此，这项研究直接将胎盘功能的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.