title: Multiple independent colonization of the Canary Islands by the winged grasshopper genus Sphingonotus Fieber, 1852.
abstract: Volcanic archipelagos represent ideal systems to study processes of colonization, differentiation and speciation. The Canary Islands are one of the best studied archipelagos, being composed of seven main islands with a well-known geological history. Most taxa have colonized these islands stepwise from the African or Iberian mainland from east to west, following their geological origin as well as the predominating wind direction and ocean currents. Furthermore, within-island radiations have been reported for several taxa. The grasshopper genus Sphingonotus is species-rich and occurs with nine fully winged species on the Canary Islands, seven of which are endemic to single or few islands. We inferred a phylogeny of these species and their North African and Iberian relatives based upon sequences of three mitochondrial genes and one nuclear gene of 136 specimens. Surprisingly, our results suggest that almost all Sphingonotus species colonized the archipelago independently from the mainland and nearly no inter-island colonization occurred. Despite their strong flight capabilities, only one pair of endemic species are closely related (S. sublaevis from Gran Canary and S. pachecoi from Lanzarote). Moreover, no within-island speciation events were detected. We hypothesize that passive wind dispersal from the African mainland was the main driver of the colonization process and that most Sphingonotus species are not able to cover inter-island distances by active flight. This, together with strong intrageneric niche overlap might explain the lack of within-island speciation in this taxon.
authors.affiliation: Department of General Zoology, Institute of Biology/Zoology, University of Halle, D-06120 Halle, Germany; Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, Technische Universität München, D-85350 Freising-Weihenstephan, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Husemann
authors.affiliation: University of Oldenburg, Department of Animal Biodiversity and Evolutionary Biology, D-26111 Oldenburg, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Deppermann
authors.affiliation: Trier University, Department of Biogeography, D-54286 Trier, Germany. Electronic address: hochkirch@uni-trier.de.
authors.forename: Axel
authors.initials: A
authors.lastname: Hochkirch
mesh_terms: D063147:Animal Distribution; D000818:Animals; D001483:Base Sequence; D017344:Genes, Insect; D050259:Genes, Mitochondrial; D006110:Grasshoppers / Q000235:genetics*; D062312:Islands; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013030:Spain; D014919:Wind
keywords: Differentiation; Island biogeography; Island colonization; Radiation; Speciation