![]() ![]() The Canary Islands are home to 124 wild bee species, including 64 endemic species and 25 subspecies, 24 of which are endemic (Hohmann et al., 1993 Kratochwil et al., 2018 Kratochwil & Schwabe, 2018b). The Madeira Archipelago is characterised by 20 wild bee species with eight endemic species and one endemic subspecies (Kratochwil et al., 2018). It is striking that to date no studies have focused on the radiation of endemic wild bees in the Macaronesian islands, though they play a key role in the pollination of many of the islands’ endemic plant species (summarised in Kratochwil & Schwabe, 2018a, Kratochwil et al., 2019, Kratochwil & Schwabe, 2020). Invertebrate studies have addressed, e.g., weevils (Machado et al., 2017), tenebrionid beetles (Juan et al., 1996a Rees et al., 2001), carabid beetles (Emerson et al., 1999, 2000a), grasshoppers (Hochkirch & Görzig, 2009 Hochkirch & Husemann, 2008 Husemann et al., 2014), mites (Salomone et al., 2002), spiders (Arnedo et al., 2001), cockroaches (Oromi et al., 1991), and molluscs (Abreu & Teixeira, 2008). Vertebrate examples on the Canary Islands include lizards (Brown & Pestano, 1998 Cox et al., 2010 Thorpe et al., 1994). Many of these taxa have undergone radiations associated with island colonisation. Patterns of colonisation of the Madeira Archipelago and the Canary Islands have been inferred for a variety of vascular plants (e.g., Böhle et al., 1996 Francisco-Ortega et al., 1996 Francisco-Ortega et al., 1997 Kim et al., 1996 Juan et al., 2000 Francisco-Ortega et al., 2002 Mort et al., 2002 Percy & Cronk, 2002) and vertebrates (Cano et al., 1984 Gonzales et al., 1996 Carranza et al., 1999 Barahona et al., 2000 Brehm et al., 2003 Maca-Meyer et al., 2003), as well as many invertebrates such as Gastropoda (Henriquez et al., 1993), Araneae (Wunderlich, 1991), Diplopoda (Enghoff, 1992), Collembola (Fjellberg, 1992), Hemiptera (Lindberg, 1953), and especially Coleoptera (Dajoz, 1977 Lindberg et al., 1958 Machado et al., 2017). ![]() In addition, both the Hawaiian Archipelago (oldest island 6 Ma) and the Galápagos Islands (oldest island about 4 Ma) are much younger than Porto Santo of the Madeira Archipelago (14.3 Ma) or Fuerteventura of the Canary Islands (20.2 Ma). In contrast to the Hawaiian Archipelago or the Galápagos Islands, the Canary Islands are relatively close to the mainland, providing a prolific source of colonisation events (e.g., Fuerteventura, eastern Canary Islands: 96 km to the west coast of Africa). The Atlantic archipelagos of Madeira and the Canary Islands are excellent models for questions of island biogeo-graphy. In terms of colonisation alone, possibilities include (a) single colonisation of an ancestor followed by radiation, (b) multiple independent colonisations, (c) back colonisation to the mainland from island archipelagos, (d) additional colonisations and back colonisations within an archipelago (Kim et al., 2008), and (e) colonisations between archipelagos (Gillespie et al., 2008). The variety of observed phenomena in island radiations is extraordinarily diverse. Island radiations of animal and plant species provide the means to study the effects of ecological and evolutionary forces and to infer colonisation history, leading to currently observed patterns of differentiation (Juan et al., 2000). due to the mostly different ages of the islands and their relative proximity to each other and to the mainland (MacArthur & Wilson, 1967). Compared to isolated oceanic islands, archipelagos are much more complex, e.g. Oceanic islands represent excellent systems to answer questions of biogeography, phylogeography, and evolutionary biology. Colonisation likely led from the Canary Islands to the Madeira Archipelago and not from the mainland directly to the latter. Morphologically and morphometrically defined subspecies were not distinguishable with COI DNA sequences. wollastoni (Madeira Island) are sister species. Andrena lineolata (Tene-rife) or its putative ancestor ( A. The data do not support a simple stepping-stone model (eastern-western colonisation from the mainland, with splitting into new taxa), but suggest Andrena gomerensis (extant on La Gomera and La Palma) or its ancestor as the basal lineage from which all other taxa evolved. Mitochondrial COI sequences support the monophyly of the four species of the Canary Islands and the two species of the Madeira Archipelago and suggest a relatively young age for all taxa. Here we investigated colonisation and radiation processes in the Madeira Archipelago and the Canary Islands of the Andrena wollastoni group of bees (subgenus Micrandrena), which comprises six endemic species and five endemic subspecies on the islands. Oceanic islands have long been considered engines of differentiation and speciation for terrestrial organisms. ![]()
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