Linzer biol. Beitr. 46/2 1535-1567 19.7.2014 Andrena (Suandrena) portosanctana COCKERELL, 1922 and A. (Suandrena) maderensis COCKERELL, 1922 – new taxonomical and ecological data for two closely related endemic bee species of the Madeira Archipelago, Portugal A. KRATOCHWIL, A. SCHWABE & E. SCHEUCHL Abstract: Andrena (Suandrena) portosanctana COCKERELL, 1922, endemic to Porto Santo, Madeira Archipelago, Portugal, was described by Cockerell on the basis of three females collected in the year 1921. No further specimens were found until the year 2011, when two females of this species (collecting date 1995) were detected in a German private collection. In the year 2012 several females and, for the first time, some males were collected by two of the authors in Porto Santo (eight localities). A differential diagnosis of A. portosanctana compared to its probably closest relative A. maderensis COCKERELL, 1922 (endemic to Madeira Island) is given. Different morphological features could be demonstrated, e.g., for the following structures: length of body, wings, clypeus, pterostigma, basal area of propodeum, width of apical process of labrum basal area, puncturing of clypeus and mesoscutum, structure of apical process of labrum basal area and basal area of propodeum, colour of flagellomeres, pubescence colour of head, mesosoma, corbiculae and metasoma. It can be clearly shown that these morphological characteristics support the differentiation of two different species. Further data for A. portosanctana and A. maderensis regarding distribution ranges, habitats, flight times and specific flower-visiting behaviour as well as the role of former and recent human impact for the population size of A. portosanctana are presented. Both species are considered to be oligolectic in pollen foraging for Brassicaceae species. Aspects of the potential mainland ancestor as well as evolutionary and biogeographical aspects including other wild-bee species of the Madeira Archipelago are discussed. Given the limited pollen resources available in various Brassicaceae species, A. portosanctana is probably an endangered species with small population sizes; therefore a special conservation program should start to avoid extinction. K e y w o r d s : Andrenidae, island biogeography, species diversification, flower- visiting behaviour. Introduction COCKERELL (1922) described two Suandrena species for the Madeira Archipelago: Andrena maderensis COCKERELL, 1922 and A. portosanctana COCKERELL, 1922. In contrast to A. maderensis, which is morphologically well characterised and common on Madeira Island, until now the morphological analysis of A. portosanctana was based only on three females collected by Cockerell in January 1921 on Porto Santo Island. © Biologiezentrum Linz/Austria; download unter www.zobodat.at