BIOGEOGRAPHIA

BIOGEOGRAPHIA Ingrandisci

Lavori della Società italiana di Biogeografia Nuova serie - vol. XXIX-2008

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  • Anno: 2008
  • Formato: 17 x 24 cm.
  • Pagine: 184 pp., ill
  • ISBN: 978-88-7145-301-9

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The highest taxonomic richness of Spongillina (Porifera: Demospongiae: Haplosclerida) at the biogeographic scale is recorded from the Neotropical (63 species), Palaearctic (59 species) and Afrotropical (49 species) regions, while lower values are known in the Oriental (37 species), Australasian (33 species), Nearctic (32 species) and Oceanic Pacific Islands (5 species) (Manconi and Pronzato, 2002, 2005, 2008ab; Pronzato and Manconi, 2002).

At the continental scale the African Spongillina comprises 17 genera and 57 species belonging to 4 families, namely Malawispongiidae (2 genera, 2 species), Metaniidae (1 genus, 1 species), Potamolepidae (4 genera, 17 species), Spongillidae (9 genera, 10 species) and 1 incertae sedis genus (1 species) (Weltner, 1913; Arndt, 1936; Penney and Racek, 1968; B n rescu, 1995; de Silva and Volkmer-Ribeiro, 1998, 2001; Manconi et al., 1999, 2008; Manconi and Pronzato, 2002, 2004, 2008abc). Most species (75.8 %) are exclusive to this continent and a notable value of endemicity s.s. at the species (39.6 %) and genus level (35 %) characterises the Afrotropical region, even though several species have been recorded only once (i.e. 23 species are known only for the holotype) and only a few species are reported more than ten times (e.g. Eunapius nitens, Metania pottsi). Species richness seems to be underestimated mainly for the unexplored Madagascan subregion with only two records (i.e. Nosy Be and Mascarenas Islands). Although an endemic Afrotropical sponge fauna exists, the present-day distribution pattern is characterised by recurring disjunct ranges reflecting the history of the continent with Afro- Oriental, Afro-Australian and Afro-Neotropical lineages related to the Gondwanaland geological, climatic and hydrological vicissitudes (Manconi and Pronzato, 2002, 2008abc).

Palaearctic Africa harbours cosmopolitan, Holarctic and Afro-Palaeo- Oriental elements exclusively belonging to the family Spongillidae (Ephydatia fluviatilis, Trochospongilla horrida, Eunapius carteri) (Manconi and Pronzato, 2008c; Manconi et al., 2008). A few relic populations of Eunapius carteri saharensis inhabit isolated extremely harsh freshwater bodies of the Tassili ‘n Ajjer in the Algerian Sahara (Tuzet, 1953; Manconi et al., 2008). The southern margins of these geographic ranges, in the Saharan Nile, overlap the northernmost occurrence of tropical elements (genera Corvospongilla, Dosilia, Eunapius and Spongilla) (Manconi and Pronzato, 2008c).

The tropical zone of Sub-Saharan Africa is characterised by the richest sponge fauna in large rivers, lakes and swamps with a frequent syntopy of species belonging to different families (Manconi and Pronzato, 2008c).

Taxonomic richness strongly decreases to 7 genera belonging to 2 families in southern Africa. The rare occurrence of the circum-tropical families Metaniidae (Metania sp.) in the Okavango and Potamolepidae (Potamolepis sp., Potamophloios sp.) in the Okavango, Chobe River and Lake Nhlabane matches the southernmost margin of their range in Africa (Curtis, 1998; Heeg, 2002; Manconi and Pronzato, 2002, 2008c). Spongillidae are represented by four genera south of the Cunene-Limpopo basins. The Afro-Oriental-Australasian genus Stratospongilla seems to be restricted to KwaZulu-Natal whereas the widespread genus Trochospongilla is recorded only from Namibia (Etosha Pan) (Annandale, 1909; Arndt, 1936; Brien and Govaert-Mallebrancke, 1958). The circumtropical- temperate genus Eunapius, one of the most speciose in Africa, is known in the western part of southern Africa exclusively for the Panafrican E. nitens in the Namibian River Kuvelai (Etosha Pan), while the eastern coastal area of KwaZulu- Natal harbours E. ambiguus and Eunapius sp. apparently endemic to the River Umhloti and Lake Cubhu, respectively (Heeg, 2002; Manconi et al., 2008).

This paper aims to report on the cosmopolitan genus Ephydatia in the context of the present knowledge of African freshwater sponges biogeography.

  • Anno 2008
  • Formato 17 x 24 cm.
  • Pagine 184 pp., ill
  • ISBN 978-88-7145-301-9

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