A decade of change in the saproxylic beetle fauna of eucalypt logs in the Warra long-term log-decay experiment, Tasmania. 1. Description of the fauna and seasonality patterns

Abstract

The first decade of sequential and cyclical sampling of saproxylic beetles by means of eclector traps on 12 freshly-felled Eucalyptus obliqua logs at Warra, Tasmania has allowed documentation of a taxonomically and ecologically diverse fauna present in such logs in their early decompositional state. About half of all species are apparently undescribed—a much higher proportion than in most temperate regions. The distribution of individuals among species is typically skewed, with most species being rare and few being common. Neither obligately nor facultatively saproxylic beetles dominate the fauna, but predators predominate over other larval feeding guilds, and—in accordance with ecological theory for early successional habitats—winged species predominate over functionally flightless species. There is some suggestion that trophic structure changed over the period of the study, with the proportion of functionally flightless species increasing. The fauna shows strong seasonality. While the summer months represent the peak of occurrence for most species (in keeping with the cool-temperate climate), every month has its own particular complement of species, such that a strong seasonal cycle in assemblage composition is apparent throughout the year. The timings of emergence peaks vary among the years represented in this study by up to 2 months, with the year of latest emergence corresponding to that with the lowest mean annual maximum temperature; no signature of climate change is evident in the data-set.