Describing Fauna Before they are Lost Forever

Article | Updated 6 years ago

Caption: Female Idiosoma nigrum
Credit: Mark Harvey

It is sometimes hard to comprehend just how biodiverse the planet is.

Despite almost 300 years of progress describing the animals, plants, fungi, and other organisms, there are estimated to be over 9 million undescribed species, which is almost five times the number of described species.

This is a huge problem for conservation, as undescribed taxa are at risk of being overlooked when shaping management strategies. Sadly, many species will go extinct before science ever discovers, describes, and protects them.

This problem was a primary focus for researchers working on the shield-backed trapdoor spiders (genus Idiosoma), which are found in remnant vegetation throughout WA’s central west, from the Swan Coastal Plain near Perth, to the Wheatbelt and Murchison regions.

They feature the only spider in Australia that is on both the Western Australian state and the Commonwealth threatened species lists, Idiosoma nigrum. Like many trapdoor spiders, they are slow to recover from disturbance as they do not move far in their lifetime, produce few young per year, and take a long time to reach maturity. The magnitude of the problem for trapdoor spiders, and the evidence for their gradual decline and extinction from the landscape was recently discussed in a publication in Austral Entomology.

Caption: Female Idiosoma nigrum
Credit: Mark Harvey

The difficulty for environmental managers is that what was originally understood to be I. nigrum, was actually five species that were yet to be fully described. Some of these undescribed species had distributions that overlapped with mining and industry, and understanding if the endangered I. nigrum, or another species was present in a location became a headache for land managers, environmental consultants, ecologists, resources staff, and the general public.

The shield-backed trapdoor spiders are visually spectacular, possessing a corrugated abdomen, which is used to plug their burrows when potential predators enter uninvited. This method of defence (using their body as a shield, or phragmosis), is found in a few groups of spiders around the world. As well as their unusual bodies, the spiders create elaborate ‘moustache-like’ structures at the entrance of their burrows. This structure is a set of trip lines, which alerts the spider to the presence of prey (or predators), making them lethal ambush predators.


Originally, the shield-backed trapdoor spiders had only two described species, the aforementioned I. nigrum, and I. sigillatum. The WA Museum housed specimens of shield-backed trapdoor spiders from across their entire distribution, and close investigation of their morphology and DNA revealed a staggering amount of diversity. The group now includes 15 new species (17 in total), three of which are listed as endangered on the WA Threatened Species List.

This work highlights the value of natural history collections in maximising the impact of conservation. Without the pre-existing collections of Idiosoma, which included specimens from bushland areas that have now been cleared, the full diversity and distributions of these species would never have been understood, and their decline would be underestimated. The researchers at the WA Museum, in collaboration with researchers from other institutions are currently undertaking extensive research on trapdoor spiders and their kin, progressively describing the vast diversity of the WA fauna.

Caption: Female Idiosoma arenaceum
Image copyright WA Museum 

To freely access ‘Conservation systematics of the shield-backed trapdoor spiders of the nigrum-group (Mygalomorphae, Idiopidae, Idiosoma): integrative taxonomy reveals a diverse and threatened fauna from south-western Australia’, undertaken by researchers from the Queensland Museum, Western Australian Museum, Adelaide University and the South Australian Museum, see here.

The work was funded by the Australian Biological Resources Study (ABRS), the Australian Research Council (ARC), WA Museum, SA Museum, BHP Billiton Pty Ltd, Rio Tinto [Pilbara Iron Company Services] Pty Ltd, Biota Environmental Sciences Pty Ltd, Bioplatforms Australia (BPA), and the Gorgon Barrow Island Net Conservation Benefits Fund.

To see how Australian scientists will address the challenge of describing species over the next 10 years, you can download ‘Discovering Biodiversity: A decadal plan for taxonomy and biosystematics in Australia and New Zealand 2018–2027’