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How beetle assemblages change with altitude along the Warra–Mount Weld altitudinal transect

Beetles are helping to answer topical questions about climate change, as part of a long-term monitoring project established in 2001 on Mount Weld in southern Tasmania by World Heritage Area and Forestry Tasmania researchers.

Transects were set up, running from 100 m to 1300 m altitude, with permanent plots located at every 100 m altitude increment. Vegetation along the transect varied from lowland Eucalyptus obliqua forest, through temperate rainforest and subalpine E. coccifera forest, to alpine heath. Birds, vascular plants and invertebrates are amongst the species being monitored. Invertebrates were sampled over the course of a year using pitfall and Malaise traps, with the transect being accessed from the top down by helicopter.

Recent sorting and analysis of the beetle samples from the altitudinal transect plots, part-funded by the Australian Greenhouse Office, found 7096 individuals belonging to 484 species. Some of these species demonstrated a strong response to altitude. Ground-beetles proved to be particularly well represented in pitfall trap samples, comprising 56 species. Notonomus politulus and Chylnus ater were restricted to altitudes below 600 m, while others were abundant only above this altitude. A particular surprise was the appearance above 900 m of Calyptogonia atra, a species which belongs to a chiefly subantarctic subfamily with relatives in southern South America and New Zealand. There had been no Tasmanian records of this species since its original description from Tasmania’s west coast in the 19th Century. Interestingly, its close relative Stichonotus piceus also turned up at the top of Mount Weld, while another relative, S. leai, was more common at lower altitudes. This entire subfamily may be a good candidate for monitoring responses to climate change.

Stag-beetles also demonstrated a response to altitude. Lissotes cancroides occurred up to 700 m, while L. subcaeruleus and L. bornemisszai shared very similar distributions above 700 m, peaking near the summit of Mount Weld.

Two specimens of the taxonomically unusual ladybird Nat vandenbergae were collected on the transect. This may not sound significant until one considers that the beetle is only found in Tasmania and is so rare that only four specimens had been collected previously.

This project thus provides a baseline against which future changes in altitudinal distributions can be gauged. Soon the transect will be resampled so that any changes that have occurred during the past ten years can be determined, enabling the identification of conservation issues for our beetle fauna (and the species they interact with) as well as providing insights into the behaviour of potential pest species under changing climate scenarios.

Dr Simon Grove and Lynne Forster
(a pdf of this article is provided for download below)