Sampling along the coastal Pilbara
MSU's blog | Created 3 years ago
Employees of the Western Australian Museum are currently carrying out a five year project, using molecular tools to investigate biodiversity in the Pilbara region. The Conservation Systematics of the Western Pilbara is funded through the Net Conservation Benefits Fund, administered through the Department of Parks and Wildlife.
The project includes fieldwork to some beautiful and remote parts of Western Australia to collect specimens for the Museum’s aquatic and terrestrial collections. In September this year, six members of the Museum’s zoology staff ventured north to carry out a three-week field trip, from Broome to Exmouth. Nerida Wilson and Kim Lema collected marine invertebrates from intertidal areas, targeting marine molluscs in particular. Joel Huey, Mark Harvey, Nik Tatarnic and Corey Whisson concentrated on terrestrial habitats, targeting arachnids, insects, and land snails.
Below are a few comments and photos from this trip.
Rhagada is a genus of land snail, endemic to Western Australia and mostly found in the Pilbara region. The taxonomy is based exclusively on morphology, largely from scattered dead-taken shells. One species complex from the Port Hedland and inland areas, Rhagada richardsonii (Smith, 1874), requires molecular clarification. During the September fieldtrip, live specimens were collected for the first time from one of the type localities of this species, where the first described specimens were collected sometime prior to 1939. This is an important find for the Museum, as DNA sequence data is difficult to extract from old specimens. Recollecting specimens from the type locality allows us to preserve the tissue appropriately for molecular work. Incredibly, a specimen of this complex was also collected from close to the extremely hot town of Marble Bar, which may represent an undescribed species. These collections will allow the taxonomy of this species complex to be refined.
One of the first species of trapdoor spiders ever described from Western Australia is Aganippe occidentalis (Hogg, 1903). The original specimen, an adult male, was collected from Roebourne and the species description and name was published in 1903. While we have possible new records of this species from other parts of the western Pilbara, we were keen to learn whether the species was still present in Roebourne. Although some nice woodland was located near the township, we only managed to find a single old, disused burrow at the base of a tree, and no extant burrows were located. The decline of trapdoor spider species in the arid zone seems to be widespread, but we don’t fully understand the reasons. The area we searched for Aganippe occidentalis had been trampled by cattle and was covered in buffle grass, which may have contributed to the decline. Hopefully this species still occurs in the Roebourne area, and future field trips will continue to search for this elusive spider.
The Heteroptera, or True Bugs (identified by their sucking mouthparts), are the most diverse group of insects with incomplete metamorphosis. That is, unlike moths, wasps and flies, they do not have a pupal stage. Most species feed exclusively on specific plants, with each plant potentially harbouring its own community of bugs. Despite their importance in the ecosystem they remain poorly studied, and in Australia thousands of species have yet to be discovered and described. One goal of this fieldtrip was to collect as many bug species as we could, along with plant cuttings so we could identify their hosts. Along with providing us with samples of new, undescribed bugs, this also helps us understand how plants and insects have coevolved, as well as providing an indication of the conservation status of different species (e.g., a bug on a widespread plant may be quite common, a bug on a plant with a narrow distribution might be rare). Over our three week trip, more than 300 species of bug were collected from approximately 50 different species of plants. Most of these species are not represented in the Museum collection, and through further study, several will undoubtedly be new to science.
It’s no coincidence that our trip covered the large expanse of Eighty Mile beach. It is the longest uninterrupted beach in WA, and extends for 220 kilometres! If you are an animal that likes to live on rocky shores, it is a really tough place to be. We are interested in finding out if the beach represents a barrier to movement along the coast for some animals. To test this, we collected a range of rocky shore animals (mostly snails), and will look at how populations are structured along this part of the coastline. If it is an important barrier, this needs to be taken into account when managing or protecting the animals that live there.