Abstract
In the present study we examine the geographic variation in the COI mtDNA barcode marker in eight Trichoptera species from Iceland to determine their postglacial colonisation history. The patterns in 10 of 12 Trichoptera species found in Iceland indicate distinct histories where different species show varying time since colonisation of the island and separate evolution restricted to Iceland. The Holarctic Limnephilus fenestratus and L. picturatus do not show a clear split between the Nearctic and Palaearctic. As previously reported for the parthenogenic Apatania zonella in Iceland, the species was found to have colonised the island both from the Nearctic and Palaearctic. Four of the Palaearctic species L. affinis, L. griseus, L. sparsus, and L. elegans present unique lineages in Iceland, suggesting that they were early colonisers after the last glacial period of Ice Age or during Holocene. Variation within the three other Palaearctic species reflect a recent origin. Limnephilus decipiens is a late coloniser, first recorded in 1929 in one location, and Micropterna sequax, a very recent coloniser in the 21(st) century, share identical genetic sequences with other European specimens, as previously reported for Potamophylax cingulatus, which is known to have colonised Iceland in the last century. Five of the 10 species suggest unique mtDNA lineages in Iceland and early colonisation.