Out of India, thrice: diversification of Asian forest scorpions reveals three colonizations of Southeast Asia

Abstract

The ‘Out of India’ hypothesis is often invoked to explain patterns of distribution among Southeast Asian taxa. According to this hypothesis, Southeast Asian taxa originated in Gondwana, diverged from their Gondwanan relatives when the Indian subcontinent rifted from Gondwana in the Late Jurassic, and colonized Southeast Asia when it collided with Eurasia in the early Cenozoic. A growing body of evidence suggests these events were far more complex than previously understood, however. The first quantitative reconstruction of the biogeography of Asian forest scorpions (Scorpionidae Latreille, 1802: Heterometrinae Simon, 1879) is presented here. Divergence time estimation, ancestral range estimation, and diversification analyses are used to determine the origins, dispersal and diversification patterns of these scorpions, providing a timeline for their biogeographical history that can be summarized into four major events. (1) Heterometrinae diverged from other Scorpionidae on the African continent after the Indian subcontinent became separated in the Cretaceous. (2) Environmental stresses during the Cretaceous–Tertiary (KT) mass extinction caused range contraction, restricting one clade of Heterometrinae to refugia in southern India (the Western Ghats) and Sri Lanka (the Central Highlands). (3) Heterometrinae dispersed to Southeast Asia three times during India’s collision with Eurasia, the first dispersal event occurring as the Indian subcontinent brushed up against the western side of Sumatra, and the other two events occurring as India moved closer to Eurasia. (4) Indian Heterometrinae, confined to southern India and Sri Lanka during the KT mass extinction, recolonized the Deccan Plateau and northern India, diversifying into new, more arid habitats after environmental conditions stabilized. These hypotheses, which are congruent with the geological literature and biogeographical analyses of other taxa from South and Southeast Asia, contribute to an improved understanding of the dispersal and diversification patterns of taxa in this biodiverse and geologically complex region.

Dipterocarps used India as a raft from Gondwana to Eurasia

“…(2007) and Ali & Aitchison (2008) India brushed up against Sumatra and collided with the Dazhuqu Arc (intra-oceanic arc), around 55 Ma in the Neo-Tethys Ocean, eventually moving closer to Eurasia until its final collision, around 34 Ma. Initial contact of India with Sumatra was also suggested by a recent study on the diversification of Asian forest scorpions (Loria & Prendini, 2020), in which dispersal from India was speculated to have happened thrice.…”

“…Distribution patterns of many Asian lineages have been explained via the out‐of‐India hypothesis wherein the Southeast Asian lineages are postulated to have originated from Gondwana with the Indian subcontinent playing a crucial role. Supporting this hypothesis, an Indian origin of many Southeast Asian taxa, including birds (Cooper & al., 2001), lizards (Macey & al., 2000; Okajima & Kumazawa, 2010), amphibians (Bossuyt & Milinkovitch, 2001; Gower & al., 2002; Wilkinson & al., 2002), arthropods (Prendini & al., 2003; Svenson & Whiting, 2009; Klaus & al., 2010; Loria & Prendini, 2020), and plants (Conti & al., 2002; Dutta & al., 2011), have been reported. According to this hypothesis, the India‐Madagascar‐Seychelles block drifted from Gondwana carrying the Gondwanan flora and fauna and rafted northwards (around 135 Ma) until 88.5–86 Ma.…”

Mesozoic origin and ‘out-of-India’ radiation of ricefishes (Adrianichthyidae)

“…In contrast, it is also theoretically possible that the Indian taxa originated on the Indian subcontinent, and that the dispersals occurred 'out-of-India', from India to Southeast Asia, after the collision of the Indian plate with Eurasia [19,20]. It is essential to evaluate the 'into-India' versus 'out-of-India' scenarios to understand how the biodiversity in these regions of different geological origins was formed [21][22][23][24][25].…”

Diversity and distribution of Asian forest scorpions (Arthropoda, Scorpionidae, Heterometrinae) in Telangana State, India

“…Prendini and Loria (2020) established new genera -Deccanometrus and Sahyadrimetrus, to accommodate seven species in the former and six species (including two new species -Sahyadrimetrus mathewi and S. tikaderi) in the latter. Loria and Prendini (2020) have established that the Asian forest scorpions separated from their African ancestors after the Indian subcontinent plate separated from Africa, lost their range during the KT mass extinction event and got restricted to southern Western Ghats in India and the Central Highlands in Sri Lanka, recolonized Deccan Plateau and north India, and dispersed, at least three times, to Southeast Asia. The research on the Asian forest scorpions in India is limited to taxonomy and occasional sighting records (Mirza et al, 2012;Bastawade et al, 2012).…”