| Summary: | Species of Verrucaria, characterised by large spores (at least some spores exceeding 25 mu m in length), perithecia leaving pits in the rock and a pale thin thallus, form a taxonomically-difficult and poorlyknown group. In this study, such species occurring in Finland are revised, based on ITS sequences and morphology. Maximum likelihood analysis of ITS sequence data was used to examine if the species belong to the Thelidium group, as suggested by BLAST search. Twelve species are accepted in Finland: Verrucaria bifurcata sp. nov., V. cavernarum sp. nov., V. devergens, V. difficilis sp. nov., V. foveolata, V. fuscozonata sp. nov., V. karelica, V. kuusamoensis sp. nov., V. subdevergens sp. nov., V. subjunctiva, V. subtilis and V. vacillans sp. nov. Verrucaria foveolata is nested in V. subjunctiva in the phylogeny, but due to morphological and ecogeographical differences, the two taxa are treated as separate species pending further studies. Based on the analysis, the study species belong to the Thelidium group. The studied species show a rather high infraspecific morphological, but a low genetic variation. Furthermore, they show considerable overlap in their morphology and many specimens cannot be reliably identified, based on morphology only. All species arc restricted to calcareous rocks. Verrucaria alpigena, V. cinereoruh and V. bochstetteri are excluded from the lichen flora of Finland. Verrucaria gmssa is considered a species with unresolved identity. Verrucaria foveolata and V. subtilis are rather common on calcareous rocks of Finland while V. devergens and V. kuusamoensis are restricted to northern Finland. Verrucaria subjunctiva occurs mainly in northern Finland. Verrucaria bifurcata has been found only from southern Finland. Verrucaria difficilis has few localities both in SW and NE Finland. Verrucaria vaeillans is restricted to calcareous roc ks (dolomite) on the mountains of the NW corner of Finland. Verrucaria Jiacozonata, V. karelica and V. sulideveTens occur only in the Oulanka area in NE Finland. A ...
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