Phylogeography of alpine and subalpine adapted Pseudostenophylax caddisflies (Limnephilidae: Trichoptera): a strong relationship with mountain formation

Organisms that inhabit the alpine zone tend to have distribution areas that are isolated and scattered in patches, in effect 'sky islands'. We focused on Pseudostenophylax caddisflies, a typical alpine aquatic insect group. Phylogenetic analyses were conducted on all eight Japanese species, with the monophyletic lineage of each strongly supported. The traditional classification system dividing Pseudostenophylax into 'ondakensis' and 'adlimitans' species groups was also strongly supported. For the first time, the existence of a cryptic species in Hokkaido was revealed in this study. Two species of the adlimitans species group live in western Honshu, Shikoku and Kyushu, but those distribution areas are difficult to explain in terms of the current geography. The phylogenetic analyses results also closely reflected the related geological history and palaeogeography. Interestingly, Pseudostenophylax amurensis, recently recorded on the Korean Peninsula, was positioned within the Japanese lineage of the ondakensis species group. Thus, some Japanese lineages may have reversely dispersed to the Korean Peninsula. Many interesting insights can be gained from the close relationship between the genetic structure of aquatic insects adapted to alpine and subalpine regions and their palaeogeographical history.