Convergent adaptation to xeric environments in rodents

Our study aims at better understanding the molecular basis of convergent evolution associated to xeric life adaptation. Adaptation to life in desertic environment can lead to the independent acquisition of similar biological traits all with the objective to save water. This phenomenon occurred several times independently in the rodents' family, making them a great model to study convergence at the molecular scale. To study convergence at the level of gene expression, we carried out a large-scale transcriptomics study and prepared 57 libraries from 20 rodent species. For each species, kidneys from 1 to 7 individuals were collected for RNA extraction and library preparation. For all individuals, the libraries were sequenced in single-end (50nt). For one individual per species, the libraries were also sequenced in paired-end (100nt) to reach a sufficient coverage rate allowing to perform de novo transcriptome assembly. Species were classified mesic or xeric based on pluviometry values from the worldclim database (http://www.worldclim.org/) using a Bio17 value threshold of 40mm (xeric <40mm & mesic >40mm).

本研究旨在深入解析与旱生（xeric）生存适应相关的趋同演化（convergent evolution）分子基础。荒漠环境的生存适应可促使不同类群独立演化出相似的生物学性状，其核心目标均为节约体内水分。这一现象在啮齿类（rodents）类群中独立发生多次，使其成为在分子尺度上研究趋同演化的理想模型类群。为从基因表达层面解析趋同演化机制，本研究开展了大规模转录组学（transcriptomics）分析，从20个啮齿动物物种中制备了共计57个测序文库（library）。针对每个物种，我们采集1至7只个体的肾脏组织，用于RNA提取与文库制备。所有个体的测序文库均采用单端（single-end）测序模式，读长为50nt。针对每个物种的1只个体，其测序文库额外采用双端（paired-end）测序模式（读长100nt），以获得足够的测序覆盖度，支持从头转录组组装（de novo transcriptome assembly）。本研究基于世界气候（WorldClim）数据库（http://www.worldclim.org/）的降水量数据，以Bio17值40mm为阈值，将所有物种划分为旱生与湿生两类：旱生物种的Bio17值<40mm，湿生物种的Bio17值>40mm。