High Levels of Diversity Uncovered in a Widespread Nominal Taxon: Continental Phylogeography of the Neotropical Tree Frog Dendropsophus minutus

Species distributed across vast continental areas and across major biomes provide unique model systems for studies of biotic diversification, yet also constitute daunting financial, logistic and political challenges for data collection across such regions. The tree frog Dendropsophus minutus (Anura: Hylidae) is a nominal species, continentally distributed in South America, that may represent a complex of multiple species, each with a more limited distribution. To understand the spatial pattern of molecular diversity throughout the range of this species complex, we obtained DNA sequence data from two mitochondrial genes, cytochrome oxidase I (COI) and the 16S rhibosomal gene (16S) for 407 samples of D. minutus and closely related species distributed across eleven countries, effectively comprising the entire range of the group. We performed phylogenetic and spatially explicit phylogeographic analyses to assess the genetic structure of lineages and infer ancestral areas. We found 43 statistically supported, deep mitochondrial lineages, several of which may represent currently unrecognized distinct species. One major clade, containing 25 divergent lineages, includes samples from the type locality of D. minutus. We defined that clade as the D. minutus complex. The remaining lineages together with the D. minutus complex constitute the D. minutus species group. Historical analyses support an Amazonian origin for the D. minutus species group with a subsequent dispersal to eastern Brazil where the D. minutus complex originated. According to our dataset, a total of eight mtDNA lineages have ranges >100,000 km2. One of them occupies an area of almost one million km2 encompassing multiple biomes. Our results, at a spatial scale and resolution unprecedented for a Neotropical vertebrate, confirm that widespread amphibian species occur in lowland South America, yet at the same time a large proportion of cryptic diversity still remains to be discovered.

分布于广袤大陆区域及主要生物群系的物种，为生物多样性分化研究提供了独特的模式系统，但同时也为此类区域的数据采集带来了艰巨的经费、后勤与政治层面的挑战。饰树蛙属（Dendropsophus）的小饰树蛙（Dendropsophus minutus，隶属于无尾目（Anura）雨蛙科（Hylidae））是一个名义物种，在南美洲大陆广泛分布，其可能代表一个包含多个分布范围更为局限的物种的复合类群。为解析该物种复合类群分布范围内的分子多样性空间格局，我们针对分布于11个国家的407份小饰树蛙及近缘物种样本，获取了两个线粒体基因——细胞色素氧化酶I（cytochrome oxidase I，COI）与16S核糖体基因（16S ribosomal gene，16S）的序列数据，样本覆盖该类群的整个分布范围。我们通过系统发育分析与空间显性系统地理学分析，评估了支系的遗传结构并推断祖先分布区域。研究共发现43个经统计学支持的深度分化线粒体支系，其中多个支系可能代表当前尚未被认知的独立物种。包含25个分化支系的一个主要演化支，涵盖了采自小饰树蛙模式产地的样本，我们将该演化支定义为小饰树蛙复合类群。剩余支系与小饰树蛙复合类群共同构成小饰树蛙物种组。历史生物地理学分析结果显示，小饰树蛙物种组起源于亚马孙地区，随后扩散至巴西东部，而小饰树蛙复合类群正是在此区域演化形成。基于本数据集，共有8个线粒体DNA支系的分布范围超过10万平方千米，其中1个支系的分布面积近100万平方千米，涵盖多个生物群系。本研究的结果在空间尺度与分辨率上均为新热带界（Neotropical）脊椎动物研究中前所未有的，不仅证实了南美低地存在广布两栖动物物种，同时也表明仍有大量隐性多样性有待发掘。