Parallel independent shifts between lifestyles in Southern Hemisphere riffle beetles (Coleoptera: Elmidae)

Abstract

Elmidae (riffle beetles) mostly inhabit running waters and are well known as ecological indicators. Originating in the Cretaceous, they are one of the most diverse water beetle families on all continents except Antarctica. Elmids exhibit two distinct adult ecomorphotypes, which have shaped higher classification: fully aquatic Elminae and amphibious Larainae. Recent phylogenetic analyses suggested these ecomorphotypes evolved convergently, but were based on relatively few taxa, largely from the Northern Hemisphere. Using an almost complete dataset for Austral Elmidae, and the most extensive for the family, we reveal at least five independent shifts between lifestyle in riffle beetles, including three in the Southern Hemisphere, these apparently being primarily from laraine to elmine ecomorphotype. One South African laraine lineage represents a new genus and species, Dracolara inexpectata gen et sp. nov., which is described here. Our findings highlight the morphological plasticity of riffle beetles and our limited knowledge of southern African freshwater biodiversity.