大耳菊头蝠复合体的适应性分化研究

A fundamental challenge in contemporary evolutionary biology is to understand the genetic mechanisms of how organisms adapt to diverse environmental conditions. Recent advances in DNA high-throughput sequencing technologies have made it possible to adaptive evolution for non-model organisms in genomic level. The two closely related species in Rhinolophus macrotis complex (Chiroptera) with similar genetics, but obviously ecological and phenotypic variation, are ideal study system to explore genetic mechanisms of adaptive evolution. In this project, based on our previous studies on this species complex, we will collect population samples in the large geographic scale of China, and sequence their transcriptomes of special organs, as well as study on their adaptive differentiation in terms of gene expression and DNA variation. At the interspecific level, we will estimate gene expression diversity and divergence, and search for differentially expressed genes associated species differentiation and positively selected genes, as well as their metabolic pathways. At the intraspecific level, we will estimate the variation trends of gene expression among populations, and identify the key genes for adaptation, as well as search the candidate genes associated with morphological and acoustic variation and their functions. The molecular mechanisms of adaptive differentiation will be uncovered for this species complex in terms of the processes of macro- and microevolution. Our results will strengthen the understanding of adaptive evolution in animals and the formation of biological diversification at the genomic level.

解析生物对多样生态环境适应的遗传机制一直是进化生物学的根本挑战。近年来，高通量测序技术的快速发展推动了非模式生物在基因组水平上的适应性进化研究。翼手目大耳菊头蝠复合体内的两个近缘种，遗传上相似，但生态和表型上显著分化，是研究非模式生物适应性进化的理想系统。本项目在前期研究基础上，大地理尺度采集蝙蝠种群样本，开展高通量转录组测序，通过对特定组织基因表达变化和DNA变异的系统研究，在物种水平，明确近缘种的基因表达多样性及变异模式，筛选出物种分化相关的差异表达基因和受选择基因及代谢通路；在种内水平，明确种群间基因表达变化趋势，鉴定出适应不同环境，以及形态和声学表型分化相关的关键基因及功能；从宏进化角度和微进化角度综合揭示大耳菊头蝠复合体的适应性分化机制。研究结果将从基因组水平加深人们对动物适应性进化和物种多样性形成的深入理解。

近缘种是开展非模式生物适应性进化研究的理想系统。本项目以大耳菊头蝠复合体及其近缘种为研究对象，整合转录组学、简化基因组学、形态和声学表型，以及环境数据等，研究其基因表达多样性及分化模式，基因表达分歧的进化驱动力，表型分歧的分子基础及其对环境适应的分子机制等。结果表明：1）大耳菊头蝠复合体及近缘种间基因表达存在组织特异性，而非物种特异性，不同组织间呈现基因表达多样性及富集通路的差异；基因表达分歧广泛受到选择作用的驱动，特别是定向选择；2）降水量和温度显著影响了大耳菊头蝠复合体及近缘种的遗传分化；3）发现大耳菊头蝠组内声波主频偏低物种中存在多个与听觉、能量代谢等相关的正选择基因，揭示其声波主频偏低表型形成的潜在分子基础；4）发现大耳菊头蝠复合体内两个近缘种的MHCII类DRB基因发生了独立的适应性进化；5）明确马铁菊头蝠不同遗传谱系种群的耳蜗组织基因表达差异显著，但与系统发育关系不一致；结合声波主频和前臂长数据，揭示出差异表达基因显著富集到突触、神经元、膜和离子转运蛋白功能等，且检测到多个与纤毛形成、免疫等相关的受正选择位点；6）发现不同声波类型蝙蝠耳蜗基因表达存在显著差异，表明发射横频声波蝙蝠耳蜗中可能存在独特的神经系统活动和丰富的离子转运活动；同时发现发回声定位的动物类群中存在多个受正选择的与听觉密切相关的差异表达基因；7）揭示大耳菊头蝠和中蹄蝠种群遗传分化的进化驱动力，其中感官驱动在大耳菊头蝠遗传变异中发挥重要作用，种群殖民历史、环境条件和地理距离在中蹄蝠遗传分化中扮演着重要角色。上述研究结果从基因组水平阐明了大耳菊头蝠复合体及近缘种基因表达变异多样性和对环境适应的分子机制，对深入揭示动物适应性进化和物种多样性形成具有重要意义。