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杰克·赛斯博士和艾莉森·怀廷夫人提供了一项资助，用于研究一群南部非洲蜥蜴失去肢体的进化模式。肢体丧失是一种在许多鳞片类群中可以看到的趋势，包括蛇和各种蜥蜴。蜥蜴科(石龙科)可以说是研究肢体丧失模式和过程的最佳系统，因为肢体减少(在某种程度上)被认为发生了30多次独立的情况。南部非洲的Scelotes属包含表现出全面的肢体减少的物种，从功能齐全的五指肢体(即有5个脚趾的肢体)到完全缺乏肢体的物种，有许多中间形式。然而，斯基克之间的进化关系尚不清楚。这项研究的目的是利用DNA序列和骨骼数据，建立一个关于南部非洲Sincines内系统发育(即系谱)关系的可靠假说，并根据系统发生学来评估Scelotes内肢体缺失的进化模式。初步结果支持这一群体中肢体缺失的多次发生和逆转。长期以来，蛇和多个蜥蜴群体的肢体缺失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之相关的形态变化，以及导致肢体丧失的生态压力，也可能间接帮助科学家了解蛇的起源细节。此外，研究多次发生肢体缺失的人群，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.