Across the Indian Ocean: A remarkable example of trans-oceanic dispersal in an austral mygalomorph spider

Abstract

The Migidae are a family of austral trapdoor spiders known to show a highly restricted and disjunct distribution pattern. Here, we aim to investigate the phylogeny and historical biogeography of the group, which was previously thought to be vicariant in origin, and examine the biogeographic origins of the genus Moggridgea using a dated multi-gene phylogeny. Moggridgea specimens were sampled from southern Australia and Africa, and Bertmainus was sampled from Western Australia. Sanger sequencing methods were used to generate a robust six marker molecular dataset consisting of the nuclear genes 18S rRNA, 28S rRNA, ITS rRNA, XPNPEP3 and H3 and the mitochondrial gene COI. Bayesian and Maximum Likelihood methods were used to analyse the dataset, and the key dispersal nodes were dated using BEAST. Based on our data, we demonstrate that Moggridgea rainbowi from Kangaroo Island, Australia is a valid member of the otherwise African genus Moggridgea. Molecular clock dating analyses show that the inter-specific divergence of M. rainbowi from African congeners is between 2.27–16.02 million years ago (Mya). This divergence date significantly post-dates the separation of Africa from Gondwana (95 Mya) and therefore does not support a vicariant origin for Australian Moggridgea. It also pre-dates human colonisation of Kangaroo Island, a result which is further supported by the intra-specific divergence date of 1.10–6.39 Mya between separate populations on Kangaroo Island. These analyses provide strong support for the hypothesis that Moggridgea colonised Australia via long-distance trans-Indian Ocean dispersal, representing the first such documented case in a mygalomorph spider.

Repeated colonization, adaptive radiation and convergent evolution in the sheet‐weaving spiders (Linyphiidae) of the south Pacific Archipelago of Juan Fernandez

“…Spiders are well‐known for their dispersal and colonizing abilities, particularly those species capable of ballooning, which has allowed them to colonize even the most remote and isolated oceanic islands (spiders can also use other long distance dispersal methods, such as rafting, e.g. see Harrison et al, 2017). By means of ballooning behaviour spiders can become airborne by releasing silk up to the point that enough drag is generated on the silk thread that the spider is lifted into the air column (Greenstone, 1990; Bell et al, 2005; Foelix, 2011; Cho et al, 2018; Morley and Robert, 2018).…”

Species conservation profile of the rare and endemic trapdoor spider Calathotarsus simoni (Araneae, Migidae) from Central Argentina

“…The spiders live in these burrows and can emerge from them to feed. They are long-lived, slow reproducing, burrowing spiders with several species of conservation concern in different parts of the world ( Harrison et al 2017 ). Members of the mygalomorph family Migidae are known from Australia, Africa, Madagascar, New Zealand, New Caledonia and the southern cone of South America: almost all parts of the former supercontinent Gondwanaland, except the Indian subcontinent and Antarctica ( Griswold and Ledford 2001 ).…”

<I>Pseudogagrella amamiana</I> (Opiliones: Sclerosomatidae) from Kanto District, Japan, as the first probable cases of domestically introduced species in Japanese harvestmen

“…Accordingly, the idea that the population might have originated from rare natural migration by rafting cannot be excluded completely. Trans-oceanic dispersal is attested in a trap-door spider genus Moggridgea occurring in both southern Australia and Africa (Harrison et al 2017). Unlike trap-door spiders that can build silk-lined burrows that may provide safe microhabitat to the spiders during long period of rafting, it is hard to envisage dispersal by rafting frequently happen in harvestmen.…”