Dysdera
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D. crocata |
Dysdera is a genus of spiders from the family Dysderidae, with more than 200 species. They occur mostly in Eurasia from Central Asia to Spain, extending into northern Africa (eg. Morocco, Egypt, Ethiopia). However, at least two species occur in South America (D. solers in Colombia (possibly a relict species from the post-miocene era) and D. magna in Brazil and Uruguay), and several species are found on smaller islands, like the Canary Islands. D. crocata is the only cosmopolitan species of the whole family.
[edit] Description
These mostly Mediterranean spiders are primarily nocturnal running hunter spiders. They spend the day in silk cocoons under stones or bark. Some species always live in caves, others do so from time to time. D. unguimannis is considered the most remarkable case of troglomorphism (adaptation to cave life) in the Dysdera genus.
[edit] Radiation in the Canary Islands
The Canary Islands are from 22 million years (Fuerteventura) to 0.8 million years (El Hierro) old. 43 endemic species of Dysdera are found on the volcanic archipelago of the Canary Islands, 100km off the northwestern coast of Africa. 36 of these species probably descended from a single ancestor; in total two to four colonization events are assumed. This probably happened by rafting, or even more likely by transport on floating islands, for Dysdera is not known to use ballooning. D. lancerotensis is the only species where an independent origin from continental ancestors is unquestionable; it was originally described as a subspecies of D. crocata. While some of the remaining Macaronesian archipelagos have been colonized from the Canaries, the Azores have been independently colonized from the continent. The radiation of Dysdera is surpassed on the Canary Islands by the snail genus Napaeus (Stylommatophora: Enidae) with more than 50 endemic species, the millipede genus Dolichoiulus (Julidae) with 46, and the beetle genera Attalus (Malachiidae) with 51 and Laparocerus (Curculionidae) with 68 endemic species.
[edit] References
- Arnedo, M.A., OromÃ, P. & Ribera, C. (2001). Radiation of the spider genus Dysdera (Araneae, Dysderidae) in the Canary Islands: Cladistic assessment based on multiple data sets. Cladistics 17(4):313-353. DOI:10.1006/clad.2001.0168 - Abstract
