School of Life Sciences, Northeast Normal University, 5268 Renmin Street, Changchun, 130024, China.
Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, 2555 Jingyue Street, Changchun, 130117, China.
Sci Rep. 2017 Apr 20;7:46542. doi: 10.1038/srep46542.
Nocturnality is a key evolutionary innovation of mammals that enables mammals to occupy relatively empty nocturnal niches. Invasion of ancestral mammals into nocturnality has long been inferred from the phylogenetic relationships of crown Mammalia, which is primarily nocturnal, and crown Reptilia, which is primarily diurnal, although molecular evidence for this is lacking. Here we used phylogenetic analyses of the vision genes involved in the phototransduction pathway to predict the diel activity patterns of ancestral mammals and reptiles. Our results demonstrated that the common ancestor of the extant Mammalia was dominated by positive selection for dim-light vision, supporting the predominate nocturnality of the ancestral mammals. Further analyses showed that the nocturnality of the ancestral mammals was probably derived from the predominate diurnality of the ancestral amniotes, which featured strong positive selection for bright-light vision. Like the ancestral amniotes, the common ancestor of the extant reptiles and various taxa in Squamata, one of the main competitors of the temporal niches of the ancestral mammals, were found to be predominate diurnality as well. Despite this relatively apparent temporal niche partitioning between ancestral mammals and the relevant reptiles, our results suggested partial overlap of their temporal niches during crepuscular periods.
夜行性是哺乳动物的一个关键进化创新，使哺乳动物能够占据相对空旷的夜间生态位。从主要是夜间活动的哺乳类冠群和主要是日间活动的爬行类冠群的系统发育关系推断，祖先哺乳动物已经长期侵入夜行性，但缺乏分子证据支持这一点。在这里，我们使用参与光转导途径的视觉基因的系统发育分析来预测祖先哺乳动物和爬行动物的昼夜活动模式。我们的结果表明，现存哺乳动物的共同祖先主要受到暗光视觉的正选择，支持祖先哺乳动物的主要夜行性。进一步的分析表明，祖先哺乳动物的夜行性可能来自于祖先羊膜动物的主要日间活动，其具有对强光视觉的强烈正选择。与祖先羊膜动物一样，现存爬行动物和有鳞目（Squamata）的各种分类群的共同祖先也被发现主要是日间活动，有鳞目是祖先哺乳动物时间生态位的主要竞争者之一。尽管祖先哺乳动物和相关爬行动物之间存在相对明显的时间生态位划分，但我们的结果表明，它们的时间生态位在黄昏时段存在部分重叠。
