Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota, United States of America.
PLoS One. 2012;7(6):e39429. doi: 10.1371/journal.pone.0039429. Epub 2012 Jun 27.
Geckos are well known for their extraordinary clinging abilities and many species easily scale vertical or even inverted surfaces. This ability is enabled by a complex digital adhesive mechanism (adhesive toepads) that employs van der Waals based adhesion, augmented by frictional forces. Numerous morphological traits and behaviors have evolved to facilitate deployment of the adhesive mechanism, maximize adhesive force and enable release from the substrate. The complex digital morphologies that result allow geckos to interact with their environment in a novel fashion quite differently from most other lizards. Details of toepad morphology suggest multiple gains and losses of the adhesive mechanism, but lack of a comprehensive phylogeny has hindered efforts to determine how frequently adhesive toepads have been gained and lost. Here we present a multigene phylogeny of geckos, including 107 of 118 recognized genera, and determine that adhesive toepads have been gained and lost multiple times, and remarkably, with approximately equal frequency. The most likely hypothesis suggests that adhesive toepads evolved 11 times and were lost nine times. The overall external morphology of the toepad is strikingly similar in many lineages in which it is independently derived, but lineage-specific differences are evident, particularly regarding internal anatomy, with unique morphological patterns defining each independent derivation.
壁虎以其非凡的附着能力而闻名,许多种类的壁虎可以轻松地爬上垂直甚至倒置的表面。这种能力是通过一种复杂的数字粘附机制(粘附趾垫)实现的,该机制利用范德华力的粘附,并增强了摩擦力。为了促进粘附机制的部署、最大化粘附力并使壁虎能够从基质上释放,已经进化出了许多形态特征和行为。复杂的数字形态使壁虎能够以新颖的方式与环境相互作用,与大多数其他蜥蜴截然不同。趾垫形态的细节表明,粘附机制已经多次获得和失去,但缺乏全面的系统发育阻碍了确定粘附趾垫获得和失去的频率的努力。在这里,我们展示了壁虎的多基因系统发育,包括 118 个公认属中的 107 个属,并确定粘附趾垫已经多次获得和失去,而且令人惊讶的是,获得和失去的频率大致相等。最有可能的假设表明,粘附趾垫进化了 11 次,失去了 9 次。在许多独立衍生的谱系中,趾垫的整体外部形态惊人地相似,但也存在谱系特异性差异,特别是在内部解剖结构方面,每个独立衍生都有独特的形态模式。