Taxonomy of the Verrucaria kalenskyi – V. xyloxena species complex in Finland

Abstract

The taxonomy of species related to Verrucaria kalenskyi and V. xyloxena in Finland was studied using morphological characters and analyses of the ITS region. Nine species are accepted as part of the V. kalenskyi – V. xyloxena -complex: V. danica, V. inverecundula sp. nov., V. juankoskiensis sp. nov., V. kalenskyi, V. kiskoensis sp. nov., V. raesaenenii sp. nov., V. tallbackaensis sp. nov., V. aff. trabicola and V. xyloxena. The species group is characterised by relatively small perithecia and spores, a predominantly brown non-areolate thallus and their similarity in the nuclear ITS region. Only V. inverecundula differs from all other species in this group by a pale endolithic thallus and shorter involucrellum. All species are restricted to calcareous rocks and/or pebbles except V. xyloxena, which occurs mainly on calcareous soils, and V. aff. trabicola, which is epiphytic. Although morphologically similar V. modica sp. nov. is not part of the V. kalenskyi – V. xyloxena complex according to our ITS-genetree. In the ITS all other taxa of the complex form a strongly supported monophyletic clade. Verrucaria kalenskyi and V. xyloxena share almost identical ITS sequences, but are morphologically distinct. Most species treated in this study resemble V. kalenskyi but differ from that species in the following features: Verrucaria danica has a fimbriate prothallus, smaller perithecia and thinner involucrellum, V. juankoskiensis has broader spores, a poorly developed thallus and more sparsely occurring perithecia, V. kiskoensis has a thicker thallus and narrower spores, V. modica has a thicker involucrellum, V. raesaenenii has a fimbriate prothallus and perithecia often leaving pits in the substratum, and V. tallbackaensis has thalline covered, more sparsely occurring and slightly larger perithecia. Occurrences of V. xyloxena on calcareous pebbles are confirmed. Most studied species are very rare in Finland except for V. kalenskyi and V. xyloxena. Occurrences of V. danica, V. juankoskiensis, V. kalenskyi and V. raesaenenii are also confirmed from Norway. Verrucaria amylacea and V. anceps are excluded from the Finnish lichen biota. A lectotype is selected for V. danica.