Holmes Michael W, Boykins Genevieve K R, Bowie Rauri C K, Lacey Eileen A
Department of Biology, Coastal Carolina University, Conway, South Carolina, 29528.
Museum of Vertebrate Zoology, University of California, Berkeley, California, 94720.
J Morphol. 2016 Jan;277(1):96-106. doi: 10.1002/jmor.20482. Epub 2015 Oct 29.
Determining how species respond to prolonged environmental change is critical to understanding both their evolutionary biology and their conservation needs. In general, organisms can respond to changing environmental conditions by moving, by adapting in situ, or by going locally or globally extinct. Morphological changes, whether plastic or adaptive, are one way that species may respond in situ to local environmental change. Because cranial morphology is influenced by selective pressures arising from an organism's abiotic and biotic environments, including aspects of thermal physiology, diet, and sensory ecology, studies of cranial morphology may generate important insights into how species are responding to environmental change. To assess potential response of deer mice (Peromyscus maniculatus) to changing conditions in the Sierra Nevada Mountains of California, we quantified cranial variation in museum specimens of this species collected approximately 100 years apart. Specifically, we examined how cranial morphology varies in three populations of this geographically widespread, ecological generalist over elevation and time. Our analyses indicate that cranial morphology does not differ with elevation within either modern or historical samples but does vary between time periods, suggesting that in situ responses to environmental change have occurred. Contrary to predictions based on Bergmann's rule, we found no consistent relationship between body size and either elevation or time, suggesting that morphological differences detected between historic and modern specimens are specific to factors influencing cranial structure. Collectively, these analyses demonstrate the potential importance of in situ changes in morphology as a response to changing environmental conditions.
确定物种如何应对长期的环境变化对于理解它们的进化生物学和保护需求都至关重要。一般来说，生物体可以通过迁移、原地适应或局部或全球灭绝来应对不断变化的环境条件。形态变化，无论是可塑性的还是适应性的，都是物种可能原地应对局部环境变化的一种方式。由于颅骨形态受到生物体非生物和生物环境产生的选择压力的影响，包括热生理学、饮食和感觉生态学等方面，对颅骨形态的研究可能会对物种如何应对环境变化产生重要见解。为了评估鹿鼠（白足鼠）对加利福尼亚内华达山脉不断变化的条件的潜在反应，我们对相隔约100年收集的该物种博物馆标本中的颅骨变异进行了量化。具体来说，我们研究了这种分布广泛、生态适应性强的物种的三个种群的颅骨形态如何随海拔和时间变化。我们的分析表明，在现代或历史样本中，颅骨形态在海拔高度上没有差异，但在不同时间段之间确实有所不同，这表明已经发生了对环境变化的原地反应。与基于伯格曼法则的预测相反，我们没有发现体型与海拔或时间之间存在一致的关系，这表明在历史标本和现代标本之间检测到的形态差异是特定于影响颅骨结构的因素的。总的来说，这些分析证明了形态原地变化作为对不断变化的环境条件的一种反应的潜在重要性。
