Chironomidae (Insecta: Diptera) Collected from Hydrilla Verticillata (Hydrocharitaceae) and other submersed aquatic Macrophytes in Lake Bisina and other Ugandan Lakes

Abstract

A survey of the aquatic weed Hydrilla verticillata was conducted in selected Kenyan and Ugandan lakes, and emerging chironomid adults were collected from samples of Hydrilla and seven other aquatic macrophytes. Hydrilla was absent from Lake Victoria, in sites where it previously occurred. Hydrilla was found in four of nine lakes examined in Uganda, i.e. Bisina, Kyoga, Bunyonyi and Mutanda. From 7424 collected chironomid adults, 43 species were identified, 21 (49%) representing new Ugandan records. Thirty-nine (91%) of the species were found on Hydrilla. Three species represent probable undescribed taxa. At our primary site, Lake Bisina, the genera Tanytarsus and Dicrotendipes dominated the chironomid community, comprising 76% of emerged adults. A species accumulation curve for chironomid species associated with Lake Bisina macrophytes suggested that further plant sampling would uncover additional species. Polypedilum wittei, formerly considered for possible biological control of Hydrilla, was not specific to that plant, emerging from six of the seven other species of submersed macrophytes we sampled. A second candidate Polypedilum species, P. dewulfi, was not found in Uganda. No insectrelated damage to Hydrilla was observed. Chironomid data were compared between Uganda collections and those from a concurrent, similar study in lake Tanganyika. Alpha- and ß-diversity values indicated that the chironomid communities on aquatic plants from Lake Bisina and Lake Tanganyika (Burundi) were markedly different. Studies of chironomids and other invertebrates associated with macrophytes in other African lakes will add significantly to knowledge of the natural history of these important aquatic environments.

Keywords: Lake Victoria, weed, biodiversity, biological control, Lake Tanganyika

Journal of East African Natural History 101(1): 29–66 (2012)