侏儒蜥属，森林变种。这只矮角变色龙拥有一种有助于使其融入林地栖息地的鳞片。森林形变体长可达7.5厘米，比其高山硬叶灌木群落形变“姊妹”体型相对较大。图片来源：Krystal Tolley

在提及吞食硬壳虫子时，侏儒蜥属广泛而多样化的物种矮蜥蜴为执行这一任务进化出令人难以置信的特殊部位：头部。

科学家长期以来想要知道为什么这些密切相关的南非蜥蜴有着如此变化多样的脑袋：一些宽，一些高，一些头部覆盖鳞片，还有一些下颌上存在装饰。

为此，他们研究了17种已知该变色龙物种中14种的饮食，并将其与蜥蜴的头部类型进行了对比。研究人员发现变色龙脑袋大小和形状与其喜好的饮食相关联，相关成果近日发表于Functional Ecology。

例如，拥有较高脑袋的林栖蜥蜴大多数吃更软的食物，其中包括蝴蝶、蜻蜓以及其他爬行动物。而那些头部拥有冠状波浪形状的变色龙则能够咬更坚硬、体型更大的昆虫。而大多数头顶没有引人注目的冠状修饰的平原蜥蜴则倾向于拥有更宽的嘴，这会帮助它们吞食体型更小但却更坚硬的类似甲壳虫的虫子。

生活在南非凡波斯平原的变色龙也比其同类林栖近亲体型更小，这可能是因为它们获得的食物比较少。颜色相对丰富的森林变形变色龙可能是这些物种的祖先，它们随着非洲南部森林的退化发生了进化。（来源：科学网 冯维维）

Does diet drive the evolution of head shape and bite force in chameleons of the genus Bradypodion?

Abstract  The head is a complex integrated system that is implicated in many vital functions. As such, its morphology is impacted by different and sometimes conflicting demands. Consequently, head shape varies greatly depending on the environment and dietary ecology of an organism. Moreover, given its role in territory defence and mating in lizards, it is also subjected to strong sexual selection in these animals. We investigated the relationships between head shape, bite performance and diet in 14 of the 17 extant Bradypodion species to determine whether variation in diet can explain the observed diversity in bite force and head shape in this genus. We also evaluate differences between sexes in terms of the relationships between head shape, bite force and diet and predict tighter relationships in females given that the head in this sex is principally under natural selection. Our results show that there is indeed a correlation between head shape, diet and bite force, but the direction and magnitude are sex-dependent. Whereas we observed a correlation between absolute bite force and head shape in both sexes, size-corrected bite force was correlated with mandible and quadrate shape in females only. Despite strong correlations between bite force and prey hardness, and between prey hardness and head shape, we did not find any relationship between head shape and prey evasiveness. These data suggest that the cranial system in chameleons of the genus Bradypodion evolves under natural selection for the ability to eat large or hard prey. Moreover, significant differences in the ecomorphological relationships between the two sexes suggest that sexual selection plays a role in driving the evolution of bite force and head shape. These data suggest that ecomorphological relationships may be sex-dependent.

原文链接：http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12750/pdf