Evolution of South Asian mountain biota: dispersal, fine-scale biogeography, phylogenetics and systematics of Nannenini jumping spiders.

The northward drift of the Indian subcontinent and its biotic exchanges with adjacent landmasses have shaped biodiversity in South Asia. We investigate biogeographic patterns and evolutionary relationships within a clade of spiders endemic to South Asia, focusing on two newly identified species from India. Specimens of the jumping spider tribe Nannenini were collected from 15 localities across the Western Ghats-Sri Lanka biodiversity hotspot, including Sri Lanka's diverse climatic regions and Kerala's tropical forests. DNA sequencing was conducted for the mitochondrial gene COI, nuclear ribosomal RNA fragments (18S and 28S), and nuclear H3. Phylogenetic analyses using maximum likelihood and Bayesian inference approaches incorporated these data with time-calibrated molecular clocks. Bayesian Evolutionary Analysis methods were used for divergence time estimation and ancestral area reconstruction. Our analyses identified a robustly supported Nannenini clade with three distinct subclades. The tribe likely originated in the Oligocene-early Miocene, with the crown lineage inheriting a distribution established by earlier stem-lineage dispersal between Southeast and South Asia. It subsequently dispersed across both regions during the Late Oligocene and Miocene, as climatic and tectonic changes promoted lineage diversification. The Late Miocene cooling and aridification likely restricted forest-adapted species to montane refugia, particularly in Sri Lanka's Central Highlands and the montane zones of India, facilitating isolation and speciation. Montane environments acted as critical refugia during adverse climatic periods, enabling the survival and diversification of isolated populations. This research enhances understanding of Salticidae evolution and highlights the influence of the Indian subcontinent's geological history on present-day biodiversity patterns in Nannenini. Additionally, we describe a new genus and two new species: Indodelaxia Jose & Benjamin, gen. nov., I. albomaculata Jose & Benjamin, sp. nov. and I. thusharagiri Jose & Benjamin, sp. nov. ZooBank: urn:lsid:zoobank.org:act:96083E0A-861F-4A31-AAE3-94A8BB983A6E.