Keystone coleopterans? Colonization by wood-feeding elmids of experimentally immersed woods in south-eastern Australia

Abstract

Macroinvertebrates on immersed woods in streams in montane south-eastern Australia respond to differences in wood taxa, according to a 4-month colonization study of experimentally positioned sticks. Xylophagous elmids (Coleoptera : Elmidae) strongly preferred local native Eucalyptus over other types of wood including non-native softer timbers (Pinus and Alnus). Where gouging elmids were abundant (in native forest streams with native riparian vegetation), immersed Eucalyptus wood supported high abundances of other macroinvertebrates; in their absence (in open grassland streams), Eucalyptus supported few other macroinvertebrates. Macroinvertebrate-gouged channels were present disproportionately on Eucalyptus sticks relative to other wood species. It is proposed that xylophagous elmid beetles are the principal macroinvertebrate modifiers of wood in these south-eastern Australian streams, where their gouging of channels increases surface area, thereby facilitating colonization by other macroinvertebrates and wood-decaying microorganisms and fungi.