Dissertation Research: Limb Loss And Phylogenetic Relationships In Southern African Scincine Lizards

美国国家科学基金会向杨百翰大学的 Jack Sites 博士和 Alison Whiting 夫人提供了一笔资助，用于研究一群南部非洲蜥蜴肢体丧失的进化模式。 肢体丧失是许多有鳞动物的一种趋势，包括蛇和各种蜥蜴。蜥蜴科 Scincidae（石龙子）可以说是研究肢体丧失模式和过程的最佳系统，因为假定肢体丧失（在某种程度上）已经发生了 30 多次独立的次数。 南部非洲的 Scelotes 属包含表现出全方位肢体减少的物种，从功能齐全的 pentadactyl 肢体（即具有 5 个手指的肢体）到完全缺乏肢体，具有许多中间形式。然而，石龙子之间的进化关系尚不清楚。 本研究的目的是利用 DNA 序列和骨骼数据，建立南部非洲区域内系统发育（即谱系）关系的强有力的假设，并根据系统发育评估 Scelotes 肢体丧失的进化模式。 初步结果支持该群体中多次发生肢体丧失以及肢体丧失的逆转。蛇和多种蜥蜴群体的肢体丧失长期以来一直是人们强烈关注的领域。 这项研究将有助于更好地了解与蛇相关的形态变化以及导致肢体丧失的生态压力，并间接帮助科学家了解有关蛇起源的细节。此外，研究多次发生肢体丧失的群体将为理解肢体发育所涉及的发育遗传机制奠定基础。

A grant has been awarded from the National Science Foundation to Dr. Jack Sites and Mrs. Alison Whiting at Brigham Young University to study the evolutionary patterns of limb loss in a group of Southern African lizards. Limb loss is a trend seen in many squamate groups, including snakes and various lizards. The lizard family Scincidae (skinks) is arguably the best system in which to study patterns and processes of limb loss because limb reduction (to some degree) is postulated to have occurred over 30 independent times. The southern African genus Scelotes contains species exhibiting the full range of limb reduction, from fully functional pentadactyl limbs (i.e., those with 5 digits) to complete lack thereof, with many intermediate forms. However, the evolutionary relationship among skinks is unknown. The objective of this research is to establish a robust hypothesis of phylogenetic (i.e., genealogical) relationships within southern African scincines, using both DNA sequence and skeletal data, and to evaluate the evolutionary pattern of limb loss within Scelotes in light of phylogeny. Preliminary results support multiple occurrences as well as reversals of limb loss in this group.The loss of limbs in snakes and multiple lizard groups has long been an area of intense interest. This study will lead to a greater understanding of the morphological changes associated with, and the ecological pressures that lead to limb loss, and indirectly may also help scientists understand details about the origin of snakes. In addition, studying limb loss in a group where it has occurred multiple times will lay the foundations for understanding the developmental genetic mechanisms involved in limb development.