Tracking colonization and diversification of insect lineages on islands:: mitochondrial DNA phylogeography of Tarphius canariensis (Coleoptera: Colydiidae) on the Canary Islands

The genus Tarphius Erichson (Colcoptera: Colydiidac) is represented by 29 species on the Canary Islands. The majority are rare, single-island endemics intimately associated with the monteverde (laurel forest and fayal-brezal). The Tarphius canariensis complex is by far the most abundant and geographically widespread occuring on Gran Canaria, Tenerife and La Palma. Eighty-seven individuals from the T. canariensis complex were sequenced for 111 bp of the mitochondrial DNA cytochrome oxidase I gene (COI), 597 bp of the COII gene and the intervening tRNA(lcu) gene. A neighbour-joining analysis of maximum-likelihood distances put La Palma as a single monophyletic clade haplotypes occurring within a larger clade comprising all Tenerife haplotypes. Gran Canarian haplotypes were also monophyletic occurring on a separate lineage. Using a combination of the phylogcographic pattern for T. canariensis, geological data, biogeography of the remaining species and estimated divergence times, we proposed a Tenerifean origin in the old Teno massif and independent colonizations from here to northeastern Tenerife (Anaga), Gran Canaria and La Palma. New methods of estimating diversification rates using branching times were applied to each island fauna. All islands exhibited a gradually decreasing rate of genetic diversification similar to that seen for Brachyderes rugatus (Colcoptera: Curculionidae) from the Canary Islands.