Collaborative Research: Genetic Analysis of Regressive Evolution

洞穴动物之所以吸引人，一方面是因为它们生活在奇怪的栖息地，另一方面是因为它们在黑暗中生活所经历的变化。本研究的目的是揭示洞穴生活中形态变化的原因，这可以作为一个模型系统来理解人类阑尾等结构的进化损失或减少。主要研究人员将调查洞穴种群中一种小虾类动物——Gammarus minus眼睛减少的原因。失明可能是因为有眼睛的动物在洞穴中处于不利地位，可能是因为浪费了能量；或者，失明可能仅仅是由于突变的随机累积而导致的。利用各种统计技术，主要研究人员将确定小眼睛的动物在洞穴环境中是否比大眼睛的动物有优势，以及大眼睛的动物在春季环境中是否比小眼睛的动物有优势。初步结果表明，自然选择在失明中起着关键作用。利用分子遗传学技术估计种群间的遗传差异，PI还将确定洞穴中的入侵和隔离是否频繁，以及其可预测的形态后果。该项目的实地工作将在西弗吉尼亚州和弗吉尼亚州的一系列洞穴和泉水中进行。

Cave animals hold a fascination both because of the strange habitat in which they live, and the modifications that they've undergone for life in darkness. The purpose of the present study is to unravel the cause of the morphological changes that accompany life in caves, which serves as a model system to understand the evolutionary loss or reduction of structures such as the appendix in humans. The principal investigators will investigate the cause of the reduction of eyes in cave populations of a small shrimp-like animal, Gammarus minus. Eye loss may happen either because animals with eyes are at some disadvantage in the cave, perhaps because of wasted energy; or eye loss may occur simply due to the random accumulation of mutations that reduce the eyes. Using a variety of statistical techniques, the principal investigators will determine whether animals with small eyes have any advantage over animals with large eyes in the cave environment, and whether animals with large eyes have any advantage over animals with small eyes in the spring environment. Preliminary results indicate that natural selection plays a critical role in the loss of eyes. Using techniques of molecular genetics that provide an estimate of the genetic differences among populations, the PI's will also determine if invasion and isolation in caves, with its predictable morphological consequences, has been frequent. Field work for this project will be done in a series of caves and springs in West Virginia and Virginia.