Comparison of the biogeographic origin of three terrestrial arthropod groups in the Socotra Archipelago (Yemen).

We reviewed and compared the occurrence and biogeographic origins of three arthropod groups, darkling beetles (Coleoptera, Tenebrionidae), spiders (Araneae) and butterflies (Papilionoidea) on the Socotra archipelago (Yemen). More than half of the darkling beetles (80.3%) and spiders (51.5%) are endemic to the Socotra archipelago, in contrast with only 5 species (18.5%) of butterflies. The number of non-endemic taxa is higher among those distributed widely in the Afro-Oriental region, less of taxa from Afro-Arabian or African origin. These species colonised the Archipelago by natural means, but we document also introduction through human activity. The exact distribution and evolutionary patterns still need thorough research (e.g. molecular, phylogenetic, and phylogeographic analyses).