Taxonomic diversity and biogeography of Chironomidae (Insecta: Diptera) in lakes of tropical West Africa using subfossil remains extracted from surface sediments

Abstract

Aim: This paper assesses whether chironomid (Insecta: Diptera) faunas of lakes in tropical West Africa and the central Sahara are biogeographically and ecologically sufficiently compatible with those of East African lakes to allow treating them as being derived from a single continent-wide species pool, and to justify merging regional palaeoenvironmental data sets relating species distributions to abiotic environmental factors and microhabitats into a pan-African data set. Location: Tropical West Africa (Cameroon and Gabon), central Sahara (Chad) and East Africa (Uganda, Kenya, Ethiopia). Methods: We employ three main approaches herein. First, we analyse the taxonomic diversity and distribution of larval Chironomidae in 12 regional study lakes using death assemblages of recently buried remains extracted from surface sediments. Secondly, we make taxonomic comparison with a similar analysis conducted in 73 East African lakes, and with checklists of Chironomidae species distribution in Africa. Thirdly, we present descriptions and illustrations of 21 West African morphotypes not previously encountered in surveys of East African Chironomidae based on subfossil larval remains. Results: This study involves 84 morphospecies or higher taxa, comprising 17 Tanypodinae, 14 Orthocladiinae, and 53 Chironominae (43 Chironomini; 10 Tanytarsini). As represented in our subfossil collections, the West African chironomid fauna shares at least 59 taxa (or 70.2% of faunal diversity) with the East African fauna, and a literature study also indicates that the majority of West African chironomid species are shared by the drier regions of North, East and Southern Africa. Freshwater lakes in tropical West Africa display a greater average taxon richness and diversity than freshwater lakes in East Africa, partly because Plio-Pleistocene climate variation in West Africa was more favourable to species survival and accumulation (promoting beta-diversity), and partly because current climatic and hydrological conditions in the region permit narrow niche differentiation and hence a more complex community structure (promoting alpha-diversity). Freshwater lakes in East Africa, especially those located in the semi-arid eastern Rift valleys of Kenya and Ethiopia, experience fluctuating hydrological regimes, which select for species able to tolerate a wide range of environmental conditions. Conclusion: Considerable species overlap between the larval chironomid faunas of the West and East African study lakes suggests that palaeoenvironmental calibration data sets from these two regions can be merged

The Diversity of Chironomidae (Diptera) Associated withHydrilla verticillata(Alismatales: Hydrocharitaceae) and Other Aquatic Macrophytes in Lake Tanganyika, Burundi

“…melaleuca and Dicrotendipes kribiicola have not been recorded from southern subtropical Africa. Several workers have noted the similarity of chironomid faunas across the present-day Sahelian and Sudanian zones stretching from west to central Africa, across the Nile Basin and into Kenya and Tanzania (Dejoux 1974, Saether and Ekrem 2003, Eggermont et al 2005. Current distributions also suggest a migratory connection between east and South Africa (Dejoux 1974).…”

“…In contrast, of 15 chironomid species-lists from 12 central and west African countries, a mean of 20.0% (range, 6.5Ð 40%) of the chironomid fauna was contributed by Polypedilum (Polypedilum) species (Freeman 1955c(Freeman , 1957bDejoux 1968Dejoux , 1973Dejoux , 1974Dejoux , 1976Petr 1970a ;Bidwell and Clarke 1977;Hare and Carter 1987). Eggermont et al (2005) pointed out that the chironomid fauna of West African lakes is richer than that of East AfricaÕs and suggested that environmental stability was probably a major reason for the difference. Among African Chironomidae, Polypedilum (Polypedilum) species may be particularly sensitive to environmental perturbation and less likely to successfully colonize areas that have a greater probability of exposure to extended dry periods.…”

Contribution à l’identification des larves de Chironomidae du fleuve Niger à Niamey

“…Plusieurs travaux d'inventaire de la biodiversité chironomidienne en Afrique tropicale ainsi que les recherches taxonomiques s'inscrivent dans ce cadre (Kyerematen, 2000 ;Ekrem, 2001Ekrem, , 2003. Pour faciliter l' inventaire de la biodiversité chironomidienne du fleuve Niger à Niamey, cette étude propose une diagnose basée sur les caractéristiques morphologiques généralement bien visibles et assez utilisées dans l'identification des larves de Chironomidae (Eggermont et Verschuren, 2003 ;Eggermont et Verschuren, 2004a,b ;Eggermont et al, 2005). Selon Dejoux (1984), le nombre d'espèces de Chironomidae en Afrique de l'Ouest s'élève à 96 au Togo et 31 au Niger.…”

“…L'identification des taxons est basée sur la présence des branchies, des soies, la forme de la capsule céphalique, les yeux (forme, position, nombre de paires), le mentum, les dents mandibulaires, la forme de la plaque paralabiale et la structure des antennes (Eggermont et Verschuren, 2003, 2004a, 2004bEggermont, 2004;Eggermont et al, 2005 ;Alhou, 2008).…”

“…Elle est essentiellement élaborée à partir des échantillons provenant du fleuve Niger à Niamey en se référant à la littérature déjà existante (Eggermont et Verschuren, 2003, 2004a, 2004bEggermont, 2004 ;Eggermont et al, 2005).…”