Taxonomic status and distribution of Australian caddisflies (Insecta: Trichoptera)

Abstract

This review of the status of Australian caddisflies focuses on publications from 1982 to 2022. Information is provided on new species described in that period, new keys, new descriptions of both adults and larvae, and the distribution of families and genera from states/regions and the Northern Territory. Australia’s caddisfly fauna now totals 27 families, 111 genera and 868 species, with 97.9% of species endemic to Australia (only 19 of the 868 species are known from outside Australia, mainly from the nearby island of New Guinea – Papua New Guinea and Papua Province, Indonesia); some species also extend into New Zealand and South-East Asia. The biogeography of the Australian fauna is discussed briefly in terms of “northern” and “southern” faunal elements, faunal provinces, distributional barriers, areas of highest biodiversity and refuge areas. Northern and southern elements in the Australian Trichoptera fauna are indicated. The highest biodiversity is recorded in the following states/regions: New South Wales with 263 species, northern Queensland (N-Qld) with 248 species and Victoria with 247 species. The highest endemicity is in southern Western Australia (S-WA), with 73% endemic species, followed by N-Qld with 58% and Tasmania with 57%. The lowest numbers of species have been recorded from South Australia and S-WA, with 42 and 49 species respectively.

Can a naturally depauperate Ephemeroptera, Plectoptera and Trichoptera (EPT) fauna track river degradation in south-western Australia?

“…Investigation of the distributional range (especially inland extent) of common species in relatively undisturbed streams may make it easier to separate biogeographical and habitat-related distribution from changes due to human-induced degradation. Additionally, there are potentially more EPT species in south-western Australia that are only known by voucher specimens or are not represented in taxonomic keys (Cartwright et al, 2023;Dean, 1999a) -further taxonomic work and nymph descriptions could help clarify the true species richness and aid identification (Braby & Williams, 2016).…”

“…They concluded that EPT species richness and abundance were effective at distinguishing sites by degradation level. However, Newfoundland has up to 165 EPT taxa (Lomond, 1997), substantially higher than the estimated total across south-western Australia of 67 (Cartwright et al, 2023;Dean, 1999aDean, , 2000Hynes & Bunn, 1984;Sutcliffe, 2003;Suter, 1999;Webb & Suter, 2011).…”

“…The EPT index could make a useful addition to the monitoring toolbox in south-western Australia given the numerous threats to aquatic habitats in the region, the size of the area to monitor, and the limited resources and expertise needed to interpret the index. However, south-western Australia has a naturally depauperate EPT fauna compared to the Northern Hemisphere and eastern Australia Cartwright et al, 2023;Sutcliffe, 2003). For example, Bunn and Davies (1990) found an average of 33 EPT species in 12 families in south-western streams compared to 120 species and 28 families in streams in south-eastern Australia.…”

“…Another potential issue with using the EPT index in south-western Australia is that around 70% of the EPT fauna in the region are endemic (Cartwright et al, 2023;Dean, 1999aDean, , 2000Hynes & Bunn, 1984;Sutcliffe, 2003), and the sensitivity of south-western endemic species to environmental gradients is not well established at a local level. Catchment-scale studies in south-western Australia found reduced EPT species counts in catchments with higher nutrient levels (Stewart, 2011a) and agricultural land compared to natural vegetation (Stewart, 2011b).…”