Pholcus anachoreta, Dimitrov & Ribera, 2006

Dimitrov, Dimitar & Ribera, Carles, 2007, The genus Pholcus (Araneae, Pholcidae) in the Canary Islands, Zoological Journal of the Linnean Society 151 (1), pp. 59-114 : 107-109

P. anachoreta

100km

excluding P. baldiosensis and P. corniger . The other large clade consists of the species from Gran Canaria, Fuerteventura, Lanzarote, Montaña Clara, Madeira and the species from the Macaronesian enclave in north-west Africa. These two groups are recognized as monophyletic, although possess low jackknife support.

The troglomorphic species from Tenerife, P. corniger , is basal with respect to the rest of the Macaronesian species. When P. baldiosensis is included in the analysis these two troglomorphic species form a small clade at the same basal position.

Five main clades for the Macaronesian Pholcus species were identified:

1. corniger ( P. corniger and P. baldiosensis ).

2. A western clade that includes P. mascaensis , P. intricatus , P. tenerifensis , P. knoeseli , P. roquensis and P. malpaisensis from Tenerife, P. gomerae and P. sveni from La Gomera, and P. bimbache from El Hierro.

3. A clade encompassing all the Madeira endemic species. This clade is a sister group to the central and eastern Canarian clades .

4. Central clade composed of all species from Gran Canaria, except P. edentatus .

5. Eastern clade embracing the species from Lanzarote, Montaña Clara, Fuerteventura, Pholcus vachoni from Morocco, and P. edentatus from Gran Canaria.

While the exact number of colonization events cannot be determined from these results, they nonetheless suggest that the Canarian species have resulted from local diversification processes. The Canarian species are grouped in four main clades, three of which are very similar to the groups described by Dimitrov & Ribera (2003). The unique difference is that P. baldiosensis and P. corniger are not recognized as members of the ‘ tenerifensis group’ and are grouped in the corniger clade. Of utmost interest is the species P. vachoni from Morocco. All trees suggested that it represents a back-colonization from the Canaries. Although merely a hypothesis, were it to be confirmed, it would provide another instance of back-colonization observed in spider species from this archipelago. Prior to this study, the possibility of back-colonization had only been demonstrated in the spider genus Dysdera (Dysderidae) ( Arnedo, Oromí & Ribera, 2001). Backcolonization has also been observed in the plant genus Monanthes (Crassulaceae) ( Mes, Wijers & Hart, 1997).

Another interesting observation is the positioning of the two cave-dwelling species. This is not the only case in the Canaries where a basal species was found in caves (see Oromí & Izquierdo, 1994; Arnedo et al., 2001). The role of caves as refuges for relict species has been proposed by Barr & Holsinger (1985). Therefore, this placement of P. corniger (and P. baldiosensis when included) indicates that they are most likely the remnants of relict fauna.

The monophyly of the Macaronesian Pholcus species , as well as the placement of the Madeira clade as an in-group to the Canarian species, suggests that an ancestor from the Canary Islands most likely colonized Madeira. This is consistent with the pattern of colonization used to explain the distribution of various plant genera in Macaronesia ( Trusty et al., 2005; Böhle, Hilger & Martin, 1996; Kim et al., 1996). A similar colonization pattern was discussed in the case of the spi- der genus Dysdera ( Arnedo et al., 2001) , as well as in some insect genera ( Emerson, Oromí & Hewitt, 2000).

The present study reveals the remarkable species radiation that the spider genus Pholcus has undergone throughout the Macaronesian region. All the results based on parsimony analyses of morphological characters corroborate the monophyly of the Macaronesian Pholcus species. Moreover, this study demonstrates the possible colonization of Madeira from the Canary Islands, as well as the back-colonization of the continent from the eastern islands.