Emergence phenology of Tasmanian mayflies (Ephemeroptera) in a first-order creek and comparison with northern hemisphere confamilials

Abstract

Context Australian mayflies are hypothesised to differ from those in the Northern Hemisphere by having longer, more variable emergence seasons that overlap more widely among taxa. Aim To test this hypothesis by comparing the behaviour of related northern and southern hemisphere species in similar habitats and at similar spatial scales. Methods Emergence dates were recorded fortnightly over two consecutive years, one ‘warm’ and one ‘cool’, in a rocky creek in south-eastern Tasmania, and at a coarser scale for Tasmania as whole, spanning an ∼20-year period. The results are compared with emergence patterns at two sites in the northern hemisphere climatically similar to Tasmania. Key results Durations of emergence seasons in Tasmania did not differ significantly at either the single site or whole of island scales from those in the northern hemisphere, but unlike in the latter, the start of emergence does not appear to be temperature-dependent. Conclusions Apparent regional differences are likely to result primarily from climatically inappropriate comparisons rather than from fundamental differences in behaviour. Implications Differences in the factor(s) that cue emergence suggest that the life histories of mayflies in Tasmania, and possibly elsewhere in Australia, are determined less by physiology than by aquatic ecology.