Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2.
Department of Natural History, Royal Ontario Museum, Toronto, Ontario, Canada M5S 2C6.
Proc Biol Sci. 2018 Apr 11;285(1876). doi: 10.1098/rspb.2017.2835.
Bats represent one of the largest and most striking nocturnal mammalian radiations, exhibiting many visual system specializations for performance in light-limited environments. Despite representing the greatest ecological diversity and species richness in Chiroptera, Neotropical lineages have been undersampled in molecular studies, limiting the potential for identifying signatures of selection on visual genes associated with differences in bat ecology. Here, we investigated how diverse ecological pressures mediate long-term shifts in selection upon long-wavelength () and short-wavelength () opsins, photosensitive cone pigments that form the basis of colour vision in most mammals, including bats. We used codon-based likelihood clade models to test whether ecological variables associated with reliance on visual information (e.g. echolocation ability and diet) or exposure to varying light environments (e.g. roosting behaviour and foraging habitat) mediated shifts in evolutionary rates in bat cone opsin genes. Using additional cone opsin sequences from newly sequenced eye transcriptomes of six Neotropical bat species, we found significant evidence for different ecological pressures influencing the evolution of the cone opsins. While is evolving under significantly lower constraint in highly specialized high-duty cycle echolocating lineages, which have enhanced sonar ability to detect and track targets, variation in constraint was significantly associated with foraging habitat, exhibiting elevated rates of evolution in species that forage among vegetation. This suggests that increased reliance on echolocation as well as the spectral environment experienced by foraging bats may differentially influence the evolution of different cone opsins. Our study demonstrates that different ecological variables may underlie contrasting evolutionary patterns in bat visual opsins, and highlights the suitability of clade models for testing ecological hypotheses of visual evolution.
蝙蝠代表了最大和最引人注目的夜间哺乳动物辐射之一，表现出许多视觉系统专门化的特点，以适应有限光照环境中的表现。尽管在翼手目动物中代表了最大的生态多样性和物种丰富度，但新热带地区的谱系在分子研究中采样不足，限制了识别与蝙蝠生态差异相关的视觉基因选择特征的潜力。在这里，我们研究了不同的生态压力如何介导对长波长（）和短波长（）视蛋白的长期选择变化，视蛋白是大多数哺乳动物包括蝙蝠的色觉基础的感光圆锥色素。我们使用基于密码子的似然聚类模型来检验与依赖视觉信息（例如回声定位能力和饮食）或暴露于不同光照环境（例如栖息行为和觅食栖息地）相关的生态变量是否介导了蝙蝠圆锥视蛋白基因进化率的变化。使用来自六个新热带蝙蝠物种新测序眼转录组的额外圆锥视蛋白序列，我们发现了显著的证据表明不同的生态压力影响了圆锥视蛋白的进化。虽然在高度专业化的高占空比回声定位谱系中，进化速度受到显著较低的约束，这些谱系具有增强的声纳能力来检测和跟踪目标，但 约束的变化与觅食栖息地显著相关，在那些在植被中觅食的物种中表现出更高的进化速率。这表明，对回声定位的依赖程度增加以及觅食蝙蝠所经历的光谱环境可能会对不同的圆锥视蛋白的进化产生不同的影响。我们的研究表明，不同的生态变量可能是蝙蝠视觉视蛋白中不同进化模式的基础，并强调了聚类模型在检验视觉进化的生态假设方面的适用性。
