Resurrection of Aedes (Halaedes) ashworthi Edwards 1921: Morphological Characterisation and Separation from its Sibling Aedes (Halaedes) australis (Erichson) 1842 (Diptera: Culicidae)

Abstract

The result of population crosses of members of the Ae. australis complex and the examination of the male genitalia of these populations have shown that Ae. ashworthi Edwards 1921 should be reinstated as a valid species. The parent females laid viable eggs when cross mated to males of different species, but the resulting F1 females and males were largely sterile. When F1 females were blood-fed and examined 3-8 d later, usually fewer than 10 ovarioles per ovary developed recognisable follicles and none of these formed eggs. F1 males in nearly all cases possessed half-size testes, and there was no spermatid development in the reduced testes. A few males had normalsized testes, but the spermatids were mostly tailless. The male of Ae. ashworthi can be separated from Ae. australis by the shape of the gonocoxite and the length of the gonostylus of the genitalia. The larvae of both species are identical, and the females differ only in the colour of some scale patches and the integument, which may prove to be too variable to be useful when more populations are compared. The morphological similarity of the two mosquitoes as larvae and adults supports the proposal that they should be recognised as sibling species, with Ae. ashworthi as the derived member of the Ae. australis complex. It is clear from morphological evidence, the viability of the F1 hybrids and the unusual habitat occupied by both species, that they have diverged recently.