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

<p>Based on chromosomal, molecular and morphological analyses, two new <i>Cacopsylla</i> Ossiannilsson, 1970 species are described, <i>C. lapponica</i> S. Nokkala & Ch. Nokkala, <b>sp. nov.</b> and <i>C. borealis</i> S. Nokkala et Ch. Nokkala, <b>sp. nov.</b> (Hemiptera, Psylloidea). <i>C. lapponica</i> is a rare bisexual alpine species living on <i>Vaccinium uliginosum</i> Linnaeus, 1753 above tree line on northern hills, where it forms sympatric populations with <i>C. myrtilli</i> 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 <i>C. myrtilli</i> 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. <i>C. borealis</i>, in turn, is a relatively common apomictic parthenogenetic species with 5n = 60 + XXXXX living on the same host plant, <i>Ledum palustre</i> Linnaeus, 1753, as <i>C. ledi</i> (Flor, 1861) and occasionally forming sympatric populations with it. No males have been recorded in <i>C. borealis</i>. Its distribution range reaches at least from northern Fennoscandia to Lake Baikal in the East. <i>C. borealis</i> can be distinguished from <i>C. ledi</i> 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 <i>COI</i> gene was sequenced. <i>C. lapponica</i> differs from the cohabitating <i>C. myrtilli</i> by 20 fixed nucleotide substitutions (uncor rected p-distance 3.13 %), while <i>C. borealis</i> differs from <i>C. ledi</i> 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, <i>C. lapponica</i> and <i>C. fraudatrix</i> Labina & Kuznetsova, 2012, and the other clade comprising the parthenogenetic species <i>C. borealis</i>, <i>C. myrtilli</i>, and <i>C. ledi</i>. Within this clade, <i>C. borealis</i> is more closely associated with <i>C. myrtilli</i> than with <i>C. ledi</i>.<br /></p>