The Road Travelled by Australian Trapdoor Spiders

Discovered words and photo by Mark Harvey, WA Museum ustralia is home to many unique spiders with most species occurring Anowhere else on Earth. Many have their origins in the distant past, when Australia was part of Gondwana in the Mesozoic, ca. 180 million years ago. Australia, New Zealand, South America, Africa, Madagascar, Antarctica and the Indian sub-continent, plus a few small islands, once formed a massive southern supercontinent known as Gondwana that gradually fragmented from the Jurassic, ca. 180–160 million years ago. Evidence of the connection between these continental blocks can be found in the fossil record The road travelled by Australian of some plants and animals, but most strikingly in the presence of related groups trapdoor spiders of organisms in the modern biota. But back to spiders. There are three major groups of spiders: the Mesothelae (a Australia that lives in shallow burrows with Above An undescribed species of Conothele. group of primitive spiders now only found in a flap-like lid. It was discovered by Adelaide Asia), the Mygalomorphae (trapdoor spiders University PhD student, Sophie Harrison, and their relatives) and the Araneomorphae to be most closely related to spiders of (all other spiders). The Australian the same genus from South Africa. Using timeline of Australia bumping into Asia. mygalomorphs include trapdoor, funnel- molecular sequence data, Sophie found that He also noted that there were two distinct web and mouse spiders, and tarantulas. the spider, Moggridgea rainbowi, diverged habitat preferences for Australian Conothele. Most Australian mygalomorph spiders from its African cousins sometime between Some species built burrows on tree trunks have their origins in Gondwana. The highly two and 16 million years ago – way too in tropical Australia, but others dug burrows venomous Sydney funnel-web spider (Atrax late to have been the result of Gondwanan in the soil. This second group used this robustus) and its relatives only occur in continental drift. Sophie and her co-authors amazing behavioural shift to colonise the eastern Australia (and many species are most speculated that the spider rafted its way to majority of the Australian arid zone. likely to have been impacted by the recent southern Australia on a big chunk of soil or He and his colleagues also found that disastrous fires). Mouse spiders (genus in a floating log, sealed inside its tube to there were plenty of species. Many could be Missulena) occur only in mainland Australia, avoid salt water and desiccation. This voyage recognised using morphological differences, with their nearest relatives in South America. of several thousand kilometres to a new life mostly in the adult males. But others were The spiny trapdoor spiders (family Idiopidae) in Australia is one of the longest recorded discovered using the DNA data. Distinct are found all over Australia, with their journeys of a mygalomorph spider. groups could be seen in the phylogenetic closest relatives in South America, Africa and The second pattern was studied by Joel tree (which looks like a family genealogy) Madagascar. The pygmy trapdoor spiders Huey and his colleagues from the Western and each is thought to be an independent (family Migidae) occur in eastern and south- Australian Museum, who examined the species. The variation was so great that western Australia, but also in South America, genus Conothele. It’s long been suspected it looks like there at least 60 species. And Africa and Madagascar. This pattern recurs that Conothele arrived from Asia during unfortunately not a single one of these has throughout the Australian mygalomorph the Cenozoic era when Australia was yet been named in the scientific literature. fauna suggesting that the majority of in close proximity to Asia, enabling the This diverse group awaits a detailed study families have been in Australia for at least spiders to island hop, especially when sea and the use of a good Latin dictionary to 180 million years. levels were low. Conothele is widespread find some euphonious species names. However, some recent studies have throughout south-east Asia, including The biological road to Australia has found different geographic patterns that various Indonesian islands. Joel found that been paved by ancient Gondwanan show that they haven’t been here the entire the entire Australian fauna only arrived relicts, followed by ring-ins from Asia and time and are relatively recent interlopers. some 20 million years ago. Once again, elsewhere. Mygalomorph spiders show The first pattern is that of a small migid this is way too young to be the result of a these distinct patterns, making them ideal spider found on Kangaroo Island in South Gondwanan origin but perfectly fits the subjects of further study. LANDSCOPE 11.

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