文獻來源: Thompson GG, Clemnte CJ, Withers PC, Fry BG. 2008. Is body shape of varanid lizards linked with retreat choice? Australian Journal of Zoology 56: 351-362. [線上摘要]蜥蜴的體型與大小倒底被什麼樣的發育, 演化以及環境因子所影響, 一直是演化生態學者有興趣的課題. 巨蜥屬內在體型以及"撤退選擇行為"(retreat choice)上的多樣化在脊椎動物中是相當特別的例子. 所謂的retreat choice其實就是指遇到危險時所採取的策略, 而這篇文章的目的就是想釐清各式巨蜥的體型大小與快閃策略是否具有關聯性. 他們將巨蜥閃躲時的策略分成四種: 藏進石縫中, 閃進地道裏, 跑進石頭下或樹洞中, 或直接溜到樹上. 他們使用了25種印度洋澳太區的巨蜥做為研究對象, 利用1038bps的NADH-2 gene序列重建牠們之間的演化關係, 然後再將針對這四種行為映象在這個演化關係上是否呈現逢機分布進行統計分析. 結果顯示會閃進石縫裏的巨蜥具有較扁平的身體與較長的尾部, 而土遁種類的前後足上臂較長. 然而不同的快閃策略與親緣關係無關, 這也就是說體型大小與快閃方式的選擇比起棲地類型等因素關聯較強. 但是這篇文章也指出不同的快閃策略倒底是演化的起因或產物還有待討論. 此外, 這篇文章也提供飼養者另一個思考方向, 也就是針對"樹棲"或"地棲"種類營造不同的人工飼養環境時, 應該要更全面地考量巨蜥各種行為的需求, 而不只是飼主的方便.
Abstract
In our earlier analysis of Varanus body shape, size was a dominating factor with some qualitative phylogenetic patterns and grouping of species into ecological categories. With a phylogeny and an improved capacity to account for the effects of size, we have reanalysed our morphometric data for male Australian goannas (Varanus spp.) using an increased number of specimens and species to examine whether variations in body shape can be accounted for by retreat choice, as it can for Western Australian Ctenophorus dragon lizards. After accounting for body size in the current analysis, four ecotypes based on retreat choice (i.e. those that retreat to oblique crevices between large rocks or rock faces, those that retreat to burrows dug into the ground, those that retreat to spaces under rocks or in tree hollows, and those that retreat to trees but not tree hollows) accounted for much of the variation in body shape. There is a phylogenetic pattern to the ecotypes, but accounting for phylogenetic effects did not weaken the link between body shape and ecotype based on retreat choice. This suggests that there are large differences in body shape among ecotypes, and shape is relatively independent of phylogeny. The strong link between shape and choice of retreat site in Varanus spp. is consistent with that for Ctenophorus spp. We speculate on why there might be a strong link between retreat choice and body shape for both Varanus and Ctenophorus.
圖片連結: Thor Hakonsen的flickr相本
