Phylogeography of the Bent-Toed Geckos (Squamata: Gekkonidae) Reveals Complex Diversification Patterns Linked to the Orogenic History of the Himalayas

Abstract

The evolutionary history of the Himalayan biota has been shaped by geological and climatic changes over time. The Himalayan bent-toed geckos, Cyrtodactylus (Squamata: Gekkonidae), is an ideal group to study the phylogeography of the Himalayas due to its early origin, wide distribution, and ongoing diversification across its range. However, the specific impact of geological events on the diversification of Central Himalayan Cyrtodactylus has not been fully investigated. In this study, we sampled Cyrtodactylus from the Central Himalayan region and analyzed concatenated mitochondrial (NADH dehydrogenase 2, 1038 bp) and nuclear (phosducin [PDC], 393 bp, and recombination activating gene, 861 bp) DNA sequences totaling 2292 bp. We complemented these by the sequences from the Himalayan and the Indo-Burma regions. Phylogenetic analyses revealed that the Cyrtodactylus samples from the Himalayan region are grouped into four major groups: C. lawderanus group, C. fasciolatus group, C. peguensis group, and C. khasiensis group. The geckos sampled in this study from the Central Himalayas belonged to the C. fasciolatus and C. khasiensis groups. Our results indicate that Cyrtodactylus underwent radiation events from the early Eocene to the late Pleistocene, with a relatively constant rate of divergence but a significant deviation from a constant rate of lineage accumulation. These findings establish a complex relationship between gecko diversification and the orogenic process of the Himalayas, which created a diverse landscape, global climate changes that led to different environments, intermittent arid conditions, shifting south Asian monsoon patterns, and the evolution of rivers. These factors facilitated allopatric speciation in the Himalayan region. Our results support a west to east diversification pattern within the range of Cyrtodactylus. Further extensive sampling and integrated genetic and ecological analyses are warranted to understand the evolution of the least studied herpetofauna of the Central Himalayan region.