Description of two new species of the genus Cacopsylla Ossiannilsson, 1970 (Hemiptera, Psylloidea) from northern Fennoscandia recognized by morphology, cytogenetic characters and COI barcode sequence

Abstract. Based on chromosomal, molecular and morphological analyses, two new Cacopsylla Ossiannilsson, 1970 species are described, C. lapponica S. Nokkala & Ch. Nokkala, sp. nov. and C. borealis S. Nokkala et Ch. Nokkala, sp. nov. (Hemiptera, Psylloidea). C. lapponica is a rare bisexual alpine species living on Vaccinium uliginosum Linnaeus, 1753 above tree line on northern hills, where it forms sympatric populations with C. myrtilli W. Wagner, 1947. So far, the species has been found in northern Finland, Utsjoki and Kilpisjärvi, and in northern Sweden, Abisko. The chromosome number in males is 2n = 12+X(0), characteristic of psyllids. The species is easily distinguished from C. myrtilli by its conspicuously smaller size mainly due to difference in wing size. Additional morphological differences are found in the length of antennae, female genital plates and male parameres. C. borealis, in turn, is a relatively common apomictic parthenogenetic species with 5n = 60 + XXXXX living on the same host plant, Ledum palustre Linnaeus, 1753, as C. ledi (Flor, 1861) and occasionally forming sympatric populations with it. No males have been recorded in C. borealis. Its distribution range reaches at least from northern Fennoscandia to Lake Baikal in the East. C. borealis can be distinguished from C. ledi by differences in the length and width of antennae, dark brown markings on the wing and female terminal structures. For molecular analysis, a 638 bp fragment of the mitochondrial COI gene was sequenced. C. lapponica differs from the cohabitating C. myrtilli by 20 fixed nucleotide substitutions (uncor rected p-distance 3.13 %), while C. borealis differs from C. ledi by 21 fixed nucleotide substitutions (uncorrected p-distance 3.29 %). Molecular phylogeny construction (ML and BI) reveals two highly divergent clades, one comprising two bisexual species, C. lapponica and C. fraudatrix Labina & Kuznetsova, 2012, and the other clade comprising the parthenogenetic species C. borealis, C. myrtilli, and C. ledi. Within this clade, C. borealis is more closely associated with C. myrtilli than with C. ledi.