Anostracans (Branchiopoda) of Botswana: Morphology, Distribution, Diversity, and Endemicity

Abstract

Including the present update, 14 anostracan species, belonging to Streptocephalus (8), Branchipodopsis (3), and Branchinella (3) are currently reported from Botswana. Branchinella spinosa and Branchipodopsis kalaharensis are the only species not occurring in neighboring southern African countries, with only the latter being a true endemic to Botswana. Streptocephalus cf. bidentatus and S. cf. cladophorusldendrophorus, distinct morphs close to the South African S. bidentatus, and to both S. dendrophorus and S. cladophorus, respectively, are additions to the fauna of Botswana, but are not given specific status. Branchinella ondonguae is also reported for the first time from Botswana. Higher species richness (33) and endemicity (64%) in South Africa are attributed to greater habitable surface area, topographic and environmental heterogeneity, and research effort. A high degree of overlapping ranges of cognate species is observed, and 2 pairs of sister species (Streptocephalus macrourus/S. cf. bidentatus and S. cafer/S. indistinctus) were found in syntopy. The occurrence of specimens with intermediate or odd morphology in the presence of, or in the area of overlap of, supposed parental species, suggests natural hybridization between S. cafer X S. indistinctus, and between S. macrourus Ã� S. cf. bidentatus. No species were found in areas with less than 350 mm of mean annual rainfall. Species of Branchipodopsis are the only anostracans in often clear, short-lived rock pools. Expanding agricultural and mining industries, roadworks, together with inappropriate conservation management, are the most important threats to the temporary pool habitats in Botswana.Botswana constitutes a major gap in our knowledge of the species composition and distribution of anostracans in southern Africa, inhibiting sound biogeographic interpretations. Most species recorded from Botswana to date were collected near the eastern and southern borders (Daday, 1910; Barnard, 1929; Hamer et al., 1994b) and from the northern Kalahari (Barnard, 1935). For some of these species, descriptions need to be amplified with additional characters that have proved their usefulness in the last decade. Furthermore, there is a need of detailed analyses of species distributions and morphology in a defined environmental context. This may provide insight into species affinities, specific ecological tolerances, and processes that cause and maintain current species and morphological diversity in ephemeral and unpredictable habitats.In this paper, we present the findings of recent collections of specimens and mud containing resting stages from about 200 localities in Botswana, including many previously unsampled areas (Fig. 1). We sampled a variety of temporary habitats, such as ditches, mud pools, rock pools, salt pans, artificial flood plains, and dams. MATERIALS AND METHODSSpecimens obtained from mud with resting stages were raised in the laboratory by inundation with distilled water at 25°C. Animals were fed ad libitum microalgae (Selena.rtrum capricorn...