Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal.
Département de Biologie Animale et Ecologie, Faculté des Sciences, Université de Mahajanga, Mahajanga, Madagascar.
Mol Phylogenet Evol. 2024 Apr;193:107997. doi: 10.1016/j.ympev.2023.107997. Epub 2023 Dec 20.
Madagascar exhibits extraordinarily high level of species richness and endemism, while being severely threatened by habitat loss and fragmentation (HL&F). In front of these threats to biodiversity, conservation effort can be directed, for instance, in the documentation of species that are still unknown to science, or in investigating how species respond to HL&F. The tufted-tail rats genus (Eliurus spp.) is the most speciose genus of endemic rodents in Madagascar, with 13 described species, which occupy two major habitat types: dry or humid forests. The large species diversity and association to specific habitat types make the Eliurus genus a suitable model for investigating species adaptation to new environments, as well as response to HL&F (dry vs humid). In the present study, we investigated Eliurus spp. genomic diversity across northern Madagascar, a region covered by both dry and humid fragmented forests. From the mitochondrial DNA (mtDNA) and nuclear genomic (RAD-seq) data of 124 Eliurus individuals sampled in poorly studied forests of northern Madagascar, we identified an undescribed Eliurus taxon (Eliurus sp. nova). We tested the hypothesis of a new Eliurus species using several approaches: i) DNA barcoding; ii) phylogenetic inferences; iii) species delimitation tests based on the Multi-Species Coalescent (MSC) model, iv) genealogical divergence index (gdi); v) an ad-hoc test of isolation-by-distance within versus between sister-taxa, vi) comparisons of %GC content patterns and vii) morphological analyses. All analyses support the recognition of the undescribed lineage as a putative distinct species. In addition, we show that Eliurus myoxinus, a species known from the dry forests of western Madagascar, is, surprisingly, found mostly in humid forests in northern Madagascar. In conclusion, we discuss the implications of such findings in the context of Eliurus species evolution and diversification, and use the distribution of northern Eliurus species as a proxy for reconstructing past changes in forest cover and vegetation type in northern Madagascar.
马达加斯加表现出极高的物种丰富度和特有性，同时也受到栖息地丧失和破碎化（HL&F）的严重威胁。面对这些对生物多样性的威胁，可以将保护工作集中在记录那些科学上尚未了解的物种，或调查物种对 HL&F 的反应上。毛尾鼠属（Eliurus spp.）是马达加斯加特有啮齿动物中最具多样性的属，有 13 个已描述的物种，它们占据了两种主要的栖息地类型：干燥或潮湿的森林。该属物种多样性大，与特定栖息地类型相关，使其成为研究物种适应新环境以及对 HL&F（干燥与潮湿）反应的合适模型。在本研究中，我们调查了马达加斯加北部地区毛尾鼠属的基因组多样性，该地区既有干燥的破碎森林，也有潮湿的破碎森林。从在马达加斯加北部未充分研究的森林中采集的 124 只毛尾鼠属个体的线粒体 DNA（mtDNA）和核基因组（RAD-seq）数据中，我们鉴定出一个未被描述的毛尾鼠属分类群（Eliurus sp. nova）。我们使用多种方法来验证一个新的毛尾鼠属物种的假设：i）DNA 条形码；ii）系统发育推断；iii）基于多物种合并（MSC）模型的物种界定测试；iv）系统发生分化指数（gdi）；v）种内与种间隔离的距离隔离检验；vi）比较 GC 含量模式；vii）形态学分析。所有分析都支持将未被描述的谱系识别为一个假定的独特物种。此外，我们还发现，原本只分布在马达加斯加西部干燥森林的 E. myoxinus 种，出人意料地在马达加斯加北部的潮湿森林中更为常见。总之，我们讨论了这些发现对毛尾鼠属物种进化和多样化的影响，并利用北部毛尾鼠属物种的分布作为重建过去马达加斯加北部森林覆盖和植被类型变化的代理。
