Penniket Sophie, Cree Alison
Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand,
Oecologia. 2015 Jun;178(2):427-40. doi: 10.1007/s00442-015-3239-0. Epub 2015 Feb 8.
Bergmann's rule predicts an increase in body size with decreasing environmental temperature; however, the converse pattern has been found in the majority of lizards studied to date. For these ectotherms, small body size may provide thermal benefits (rapid heat uptake when basking), which would be highly advantageous in cold environments. Yet such an advantage may not exist in nocturnal lizards (which do not avidly bask), in which Bergmann's rule has not been closely studied. We have examined whether the body size of a primarily nocturnal gecko, Woodworthia "Otago/Southland" changed with elevation and operative temperature (determined using physical copper models). In a laboratory study, we investigated whether thermoregulatory mode (heliothermy or thigmothermy) alters the effect of body size on heating and cooling rates. This gecko followed Bergmann's rule, thereby showing the opposite of the dominant pattern in diurnal lizards. Size at maturity, maximum size of adults and size at birth were larger at higher elevations and at lower operative temperatures. Using physical models, we found that large body size can confer thermal benefits for nocturnal lizards that remain within diurnal retreats. Bergmann's rule should not be dismissed for all lizards. Our results clearly support Bergmann's rule for at least one thigmothermic species, for which large body size may provide thermal benefits. Future studies on Bergmann's rule in lizards should consider thermoregulatory mode. We advocate that this ecogeographic rule be examined in relation to operative temperature measured at field sites. Finally, we predict that climate warming may weaken the relationship between body size and elevation in this gecko.
伯格曼法则预测，随着环境温度降低，体型会增大；然而，在迄今为止研究的大多数蜥蜴中发现了相反的模式。对于这些变温动物来说，小体型可能带来热优势（晒太阳时快速吸收热量），这在寒冷环境中非常有利。然而，这种优势可能在夜行性蜥蜴（不热衷于晒太阳）中不存在，伯格曼法则在这类蜥蜴中尚未得到深入研究。我们研究了一种主要夜行性的壁虎——“奥塔哥/南地”木氏壁虎的体型是否随海拔和有效温度（使用物理铜模型确定）而变化。在一项实验室研究中，我们调查了体温调节模式（日射热调节或接触热调节）是否会改变体型对加热和冷却速率的影响。这种壁虎遵循伯格曼法则，从而呈现出与昼行性蜥蜴的主导模式相反的情况。在较高海拔和较低有效温度下，成熟时的体型、成年个体的最大体型以及出生时的体型更大。通过物理模型，我们发现大体型可以为留在日间藏身之处的夜行性蜥蜴带来热优势。不能因所有蜥蜴而否定伯格曼法则。我们的结果明确支持至少一种接触热调节物种的伯格曼法则，对于该物种而言，大体型可能带来热优势。未来关于蜥蜴伯格曼法则的研究应考虑体温调节模式。我们主张结合在野外场地测量的有效温度来检验这条生态地理法则。最后，我们预测气候变暖可能会削弱这种壁虎体型与海拔之间的关系。
