A combined approach of mitochondrial DNA and anchored nuclear phylogenomics sheds light on unrecognized diversity, phylogeny, and historical biogeography of the cascade frogs, genus Amolops (Anura: Ranidae)

<p><i>Amolops</i> is one of the most species-rich genera in Ranidae, with 59 recognized species. This genus currently includes six species groups diagnosed mainly by morphology. Several recent molecular studies indicated that the classification of species groups within <i>Amolops</i> remains controversial, and key nodes in the phylogeny have been inadequately resolved. In addition, the diversity of cascade frogs remains poorly understood, especially for those from incompletely sampled regions. Herein, we investigate the species-level diversity within genus <i>Amolops</i> throughout southern China and Southeast Asia, and infer evolutionary relationships among the species using mtDNA data (16S, <i>COI</i>, and <i>ND2</i>). Molecular analyses indicate nine new unnamed species, mostly distributed in the Himalayas. We then utilized anchored hybrid enrichment to generate a dataset representing major mitochondrial lineages to resolve phylogenetic relationships, biogeography, and pattern of species diversification. Our resulting phylogeny strongly supports the monophyly of three previously identified species groups (the <i>A. ricketti</i>, <i>A. daiyunensis</i>,<i> </i>and <i>A. hainanensis</i> groups), the paraphyly of the <i>A. mantzorum</i> and <i>A. marmoratus</i> groups, as previously defined, and monophyly of the <i>A. monticola</i> group. We erect one new species group, the <i>A. viridimaculatus</i> group, and recognize Dubois (1992) 'subgenus' <i>Amo</i> as the <i>A. larutensis</i> species group. Biogeographic analysis suggests that <i>Amolops</i> originated on the Indo-Burma/Tai-Malay Peninsula at the Eocene/Oligocene boundary, and dispersed outward, exemplifying a common pattern observed for the origin of Asia's biodiversity. The early divergence within <i>Amolops</i> coincides with the Himalayas uplift, and the lateral extrusion of Indochina at the Oligocene/Miocene boundary. Our results show that paleoclimatic and geomorphological events have profoundly influenced the pattern of lineage diversification within <i>Amolops</i>.</p>