To reveal the phylogeographic pattern of the parthenogenetic psyllid Cacopsylla myrtilli (W. Wagner 1947) (Hemiptera, Psylloidea), we sequenced a 638bp fragment of the mitochondrial COI gene from 962 individuals. These insects originated from 46 sampling sites, which cover a significant part of the northern Palearctic distribution range of the species. The sequence data revealed 40 haplotypes, with three main (H1, H2, and H3) and 37 derived ones. The main haplotypes H1 or H2 or both were present at all sampling sites. The star-like shape of the haplotype networks indicated recent population expansion. In most cases, the derived haplotypes were specific for each country, suggesting that the main haplotypes H1 and H2 are of refugial origin, and the derived haplotypes have emerged after the postglacial recolonization process. Based on the haplotype sequences, we suggest H3 to represent the ancestral haplotype from which H1 and H2 have evolved. We suggest that the main haplotype H3 together with its derived haplotypes represents bisexual C. myrtilli, which shows a limited distribution on both sides of the border between Finland and Russia in northern Fennoscandia. The genetic diversity was the highest in Sjoa in southern Norway and also high in the White Sea region in northwest Russia. Higher diversity in Sjoa was attributed to both earlier recolonizations compared to that of the White Sea region and the absence of Wolbachia infection. We suggest that these sites were colonized from different Pleistocene refugia, i.e., from western and eastern refugia, respectively. From the White Sea region, recolonization continued eastwards to Ural Mountains and westwards to Finland and further north to Kola Peninsula. From northern Finland, recolonization continued to Finnmark, Norway, and further to Sweden and finally reached a secondary contact zone with colonizers from Norway in Central Sweden. The Caucasus and Siberian/Manchurian refugial regions have played an important role in the origin of C. myrtilli populations in Siberia and the Russian Far East.

Wolbachia is one of the most common intracellular bacteria; it infects a wide variety of insects, other arthropods, and some nematodes. Wolbachia is ordinarily transmitted vertically from mother to offspring and can manipulate physiology and reproduction of their hosts in different ways, e.g., induce feminization, male killing, and parthenogenesis. Despite the great interest in Wolbachia, many aspects of its biology remain unclear and its incidence across many insect orders, including Hemiptera, is still poorly understood. In this report, we present data on Wolbachia infection in five jumping plant-lice species (Hemiptera, Psylloidea) of the genus Cacopsylla Ossiannilsson, 1970 with different reproductive strategies and test the hypothesis that Wolbachia mediates parthenogenetic and bisexual patterns observed in some Cacopsylla species. We show that the five species studied are infected with a single Wolbachia strain, belonging to the supergroup B. This strain has also been found in different insect orders (Lepidoptera, Hemiptera, Plecoptera, Orthoptera, Hymenoptera, Diptera) and even in acariform mites (Trombidiformes), suggesting extensive horizontal transmission of Wolbachia between representatives of these taxa. Our survey did not reveal significant differences in infection frequency between parthenogenetic and bisexual populations or between males and females within bisexual populations. However, infection rate varied notably in different Cacopsylla species or within distinct populations of the same species. Overall, we demonstrate that Wolbachia infects a high proportion of Cacopsylla individuals and populations, suggesting the essential role of this bacterium in their biology.

The bug family Nabidae (Heteroptera) includes taxa showing either a low chromosome number 2n = 16 + XY or high chromosome numbers 2n = 26 or 32 + XY. In order to reveal the direction of karyotype evolution in the family, a molecular phylogeny of the family was created to reveal the taxon closest to the ancestral type and hence the ancestral karyotype. The phylogeny was based on a partial sequence of the 18S rDNA gene of both high and low chromosome number species belonging to the subfamilies Prostemmatinae and Nabinae. Phylogeny created by the Neighbour Joining method separated the subfamilies, Prostemmatinae and Nabinae, which form sister groups at the base of this phylogenetic tree, as well as within the Nabinae, tribes Nabini and Arachnocorini. Combining karyosystematic data with the phylogeny of the family indicated that the ancestral karyotype was a high chromosome number, consisting of 2n = 32 + XY. During the course of evolution changes have occurred both in meiotic behaviour of the sex chromosomes and in the number of autosomes. The direction of karyotype evolution was from a high to low autosome number. Abrupt decreases in the number of autosomes have occurred twice; firstly when the tribe Arachnocorini differentiated from the main stem in the subfamily Nabinae and secondly within the tribe Nabini, when within the genus Nabis 2n = 16 + XY species diverged from the 2n = 32 + XY species. A scheme of the sequence of events in karyotype evolution during the evolution of the Nabidae is presented.

For studying meiosis in males, large samples of Cacopsylla myrtilli (Wagner, 1947) (Hemiptera, Psyllidae) were collected in Norway, Sweden, Finland and northwes

Characteristics of parthenogenesis in Cacopsylla ledi (Flor, 1861) were analyzed using cytological and molecular approaches. In all three populations studied from Finland, i.e. Turku, Kustavi and Siikajoki, males were present at a low frequency but were absent from a population from Vorkuta, Russia. In a follow-up study conducted in the Turku population during 2010–2016, the initial frequency of males was ca. 10 % and showed no intraseasonal variation, but then dramatically decreased down to approximately 1–2 % level in seasons 2015–2016. Male meiosis was chiasmate with some traces of chromosomal fragmentation and subsequent fusions. In most females, metaphase in mature eggs included 39 univalent chromosomes which indicated apomictic triploidy. Only a small fraction of females was diploid with 13 chiasmate bivalents. The frequency of diploid females approximately equaled that of males. COI barcode analyses showed that triploid females (N = 57) and diploids (7 females and 5 males) displayed different haplotypes, demonstrating that triploid females reproduced via obligate parthenogenesis. The rarity of diploids, along with the lack of males’ preference towards diploid females, suggested that most likely diploids were produced by rare triploid females which shared the same haplotype with the diploids (not found in the present analysis). Minimum haplotype diversity was detected in the Turku population, but it was much higher in Vorkuta with some indication for the mixed origin of the population. We suggest that functional diploids produced in a parthenogenetic population can give rise either to a new parthenogenetic lineage or even to a new bisexual species.