The out-of-India hypothesis: evidence from an ancient centipede genus, Rhysida (Chilopoda: Scolopendromorpha) from the Oriental Region, and systematics of Indian species

Abstract

The Oriental Region has been a focus of biogeographical research for more than two centuries. We examined systematics and biogeography of the centipede genus Rhysida in this region. A robust species hypothesis for the Indian subcontinental and Southeast Asian Rhysida clade uses molecular, morphological and distribution data. Twelve species are recognized in two monophyletic species complexes, eight belonging to the Rhysida immarginata and four to the Rhysida longipes species complex. They include Rhysida aspinosa, Rhysida crassispina, R. immarginata, R. longipes and seven new species, five of which are formally named in this paper: Rhysida ikhalama, Rhysida konda, Rhysida lewisi, Rhysida pazhuthara and Rhysida sada The nine Rhysida species are documented taxonomically and their morphological variation is reviewed. An integrative systematic approach reveals that diversity of Rhysida in the Indian subcontinent has been underestimated. Both species complexes started to diversify in the Early to Late Cretaceous in the Indian subcontinent. The out-of-India hypothesis is supported in both clades, because Southeast Asian species are nested in Indian subcontinental clades. Historical biogeographical analyses suggest two independent post-collision dispersal events, one in the immarginata clade and another where R. longipes expanded its range into Southeast Asia.

Phylogenomic analyses reveal a Gondwanan origin and repeated out of India colonizations into Asia by tarantulas (Araneae: Theraphosidae)

“…Estimates surrounding the timing of the collision between the Indian Subcontinent and Asia vary, but most studies agree on a late Paleocene/early Eocene timescale around 55 Ma ( Hu et al, 2016 ; Zheng & Wu, 2018 ; Westerweel et al, 2019 ). Migrations from the Indian Subcontinent to Asia are known to have played a significant role in generating the high faunal diversity observed in Asia today ( Karanth, 2006 ; Morley et al, 2016 ; Morley, 2018 ; Garg & Biju, 2019 ), even amongst spiders ( Li, Shao & Li, 2020 ) and other invertebrates ( Joshi, Karanth & Edgecombe, 2020 ). It has also been shown that other spiders of a comparable age originated on the Gondwanan supercontinent, i.e., South America and Africa, before eventually colonizing Asia and Oceania ( Chamberland et al, 2018 ).…”

Spatial patterns of phylogenetic diversity and endemism in the Western Ghats, India: a case study using ancient predatory arthropods

“…Primary location data (n = 100) for 19 species in the three genera of the centipede family Scolopendridae (Subfamily Otostigminae): Digitipes Attems, 1930, Ethmostigmus Pocock, 1898 and Rhysida Wood, 1862 were obtained by systematic sampling across the Western Ghats (WG) from 2008 to 2010, spanning its latitudinal and elevational gradients (Joshi et al, 2020;Joshi & Edgecombe, 2013Joshi & Karanth, 2012) (see Appendix S1 in Supporting Information). These data were supplemented with opportunistic sampling which continued to 2018.…”

“…Since it is challenging to identify centipede species in the field, specimens associated with the primary location data were collected and identified in the lab based on microscopic examination of morphological characters. Species identity was also assessed through molecular phylogenetic and species delimitation analyses (Joshi et al, 2020;Joshi & Edgecombe, 2013Joshi & Karanth, 2012). State forest department permits were obtained to collect centipedes in protected areas and specimens were preserved in 70% ethanol.…”

“…TD is calculated by stacking species distributions and summing species presences for each cell, while WE is calculated by scaling species presence with its range size (number of cells in the predicted map where a species is present) and summing this across species found in a cell (Crisp et al, 2001). A species time-tree for the subfamily Otostigminae based on a combined dataset of mitochondrial and nuclear markers (Joshi et al, 2020) was used to calculate PD and PE. PD is calculated by summing up branch lengths of all species present in a cell derived from the phylogenetic tree (Faith, 1992) and we present it as the proportion of total tree length (range: 0 -1).…”

“…The WG scolopendrid community has been revised extensively by using both morphology and molecular data, resulting in the discovery of many endemic species and radiations (Joshi & Edgecombe, 2018;Joshi, Karanth & Edgecombe, 2020). It is accompanied by detailed primary distribution data spanning large latitudinal (8°N -20°N) and elevational gradients (100 -2400 meters from mean sea level (msl)).…”