Dorota Lachowska

Occurrence of Wolbachia in central European weevils: correlations with host systematics, ecology, and biology

We studied the occurrence of Wolbachia in relation to the systematics, ecology, and biology of 40 weevil species from central Europe. Identification of Wolbachia supergroups and phylogeny was performed on the basis of 16S rDNA, ftsZ, wsp, and hcpA sequences. Sixteen species (40%) were infected by Wolbachia. Six of these possess only supergroup A (15% of all studied species, 37.5% of the infected species), and four harbored only supergroup B (10 and 25%, respectively). Six species were infected by both supergroups A and B or their genomes harbored parts of these two supergroups (15 and 37.5%, respectively). No differences between Wolbachia supergroup frequencies were detected. There was almost no correlation between Wolbachia phylogeny and host systematics and phylogeny at the level of subfamily and tribe, because the representatives of both supergroups were detected in all the studied multi‐species tribes. Wolbachia strains were probably inherited from a common ancestor only in the case of the genus Strophosoma, where two of three analyzed species possessed bacteria which are genetically very close in all the studied genes. There was also only limited congruence between phylogenies obtained from the four studied genes. These results suggest horizontal transmission of Wolbachia strains between species and recombination events between different strains. A significant correlation was detected between infected and uninfected species in relation to mobility (flying species were 2×  more frequently infected than non‐flying species), foraging (polyphagous species were 2.5×  less frequently infected than mono‐ or oligophagous species), and reproductive mode (parthenogenetic weevils were infected nearly 2×  as often as bisexuals). No differences were detected between mesophilous and xerothermophilous species, nor between those inhabiting open areas vs. arboreal species. However, these results might have been influenced by common ancestry among the studied weevils. Because weevils include many plant pests of economic importance, it is possible to use these data in developing alternative, biology‐based strategies for controlling them.

Molecular phylogeny of the Mediterranean species of Philaenus (Hemiptera: Auchenorrhyncha: Aphrophoridae) using mitochondrial and nuclear DNA sequences.

The phylogenies of all eight European species of Philaenus were estimated from cytochrome oxidase subunit I, cytochrome B and internal transcribed spacer 2 (ITS2) fragments of DNA using phylogenetic reconstruction methods: maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) analyses. Based on the topologies of all obtained phylogenetic trees, the monophyly of Philaenus is well supported, being congruent with morphological, ecological and chromosomal data. Three phylogenetic lineages were distinguished in the mitochondrial and combined (mtDNA with ITS2) trees. The first lineage is represented by only one species, Philaenus maghresignus, which inhabits Maghreb and southern Spain. Clade A includes three species: P. tarifa (Southern Iberia), P. italosignus (Sicily and Southern Italy) and P. signatus (the Balkans and Middle East). In clade B two subclades were recognized: B1 represented by P. loukasi (Southern Balkans) and P. arslani (Middle East), and B2 comprising P. spumarus (the most widespread Palaearctic species) and P. tesselatus (from Southern Iberia and Maghreb). These clades were also retrieved in trees reconstructed from nuclear sequences. However, four species (P. maghresignus, P. tarifa, P. italosignus and P. signatus) showed unresolved polytomy at the base of the nuclear tree. Clade A together with P. maghresignus clustered with the ‘signatus’ group defined from morphology, and clade B with the ‘spumarius’ group; these might be considered separate subgenera. Genetic distances in mitochondrial DNA between ingroup species ranged from 14.0% between P. signatus and P. spumarius to 2.4% between P. tesselatus and P. spumarius. By contrast, genetic divergence of ITS2 between ingroup species was very low, at most 2.1%. The divergence of Philaenus species is estimated to have occcurred between 7.9 and 0.6 Ma. Possibly three main speciation events occurred: the first at the Miocene/Pliocene boundary (c. 5.5 Ma) for deeper splits; the second between 4.2 and 2.5 Ma in the Pliocene, when pairs of more closely related species diverged; and the most recent during the Pleistocene glaciations, when the separation of P. tesselatus and P. spumarius took place. The species status of all Philaenus species is confirmed except for P. tesselatus.

New data on the cytology of parthenogenetic weevils (Coleoptera, Curculionidae)

Parthenogenesis and, in particular, polyploidy are rare in animals. A number of cases, known among weevils, represent apomictic parthenogenesis—a reproductive mode in which eggs undergo one maturation division, the chromosomes divide equationally, and no reduction takes place. Among parthenogenetic weevils there are two diploids, 48 triploids, 18 tetraploids, six pentaploids, three hexaploids and one decaploid. Eight examined parthenogenetic species are triploids with 33 chromosomes of different morphology, confirming that triploidy is the most common level of ploidy in weevils. The karyotypes are heterogeneous with the presence of meta-, submeta-, subtelo- and acrocentric chromosomes. The C-banding method showed that only two species possess a large amount of heterochromatin visible as a band around the centromere during mitotic metaphase. This agrees with observations that weevils are characterized by a small amount of heterochromatin, undetectable in metaphase plates after C-banding. In three species an atypical course of apomictic oogenesis occurs with stages similar to meiosis, in which chromosomes form bivalents and multivalent clusters. This association of chromosomes probably represents the remnants of meiosis, although these events have nothing to do with recombination. The results support the hypothesis that the evolution of apomictic parthenogenesis in weevils has proceeded through a stage of automixis.

Mediterranean Species of the Spittlebug Genus Philaenus: Modes of Chromosome Evolution

Abstract The evolution of karyotypes and sex determination system of Philaenus Stål (Auchenorrhyncha: Aphrophoridae) species is studied here in detail. The most plausible scenario of chromosomal rearrangements accompanying phylogenetic differentiation in Philaenus is advanced. It is postulated that the ancestral karyotype of Philaenus was 2n = 24 + X0. Karyotype changes occurred several times independently in the genus. The karyotype of 2n = 22 + X0 (P. spumarius and P. tesselatus) originated from 2n = 24 + X0 by fusion between two autosomal pairs. The neo—XY system (P. arslani, P. loukasi, P. signatus, P. maghresignus, and P. tarifa) also originated from the 24 + X0 karyotype by means of independent fusions between autosomes and the original X chromosome. The neo—X1X2Y system (P. italosignus) evolved from the 2n = 22 + neo—XY karyotype by an additional fusion between the Y chromosome and one more autosomal pair. The neo—XnY system of P. italosignus is the first reported case of an evolutionarily fixed multiple sex chromosome system in Auchenorrhyncha.

Karyology of parthenogenetic weevils (Coleoptera, Curculionidae): Do meiotic prophase stages occur?

We investigated the cytological mechanism of parthenogenesis by analyzing the chromosomes in five weevil species. All examined species are polyploids, four of which: Otiorhynchus ovatus, Simo variegates, Cathormiocerus aristatus, and Tropiphorus elevatus possess three haploid sets of chromosomes (3n=33), whereas the fifth, Trachyphloeus parallelus, is tetraploid with 44 chromosomes (4n=44). The plates contained 27-31 chromosomes in triploid species and 38, 39, 41 and even 44 in tetraploid T. parallelus. In all species single clusters of metaphase plates with a haploid number of n=11 were visible. Some oogonial cells showed nuclei configurations resembling the stages of diplotene and diakinesis. The spiralized chromosomes in these nuclei may have been connected by chiasmata resulting in rods figures and ring-shaped bivalents. Occurrence of the remnants of meiosis could suggest some degree of recombination in parthenogenetic lineages of weevils.

Genetic diversity of Philaenus spumarius and P. tesselatus (Hemiptera, Aphrophoridae): implications for evolution and taxonomy

The meadow spittlebugs Philaenus spumarius and P. tesselatus are closely related taxa with uncertain taxonomic position in the light of previous morphological, ecological, cytological and molecular research. Despite morphological homogeneity of P. spumarius (with the exception of high colour and pattern polymorphism) across its wide Holarctic range, it is possible that additional taxa (species or subspecies) exist. Philaenus spumarius is a potentially important pest in parts of its range where it was introduced. We used DNA markers to describe the genetic diversity of P. spumarius and P. tesselatus and to verify the taxonomic status of P. tesselatus and remote populations of the former species. The mitochondrial (cytochrome B) data showed that there are two main groups encompassing a northeastern (Asia and north‐central Europe) and a southwestern (Mediterranean area and western Europe, including North American specimens) clade. According to the elongation factor‐1α gene, there are three main clades: northeastern (Eurasiatic clade, E1), southeastern (east Mediterranean – Caucasus clade, E2) and southwestern (Iberian clade, E3). These two or three mitochondrial and nuclear clades could be considered as separate taxonomic units. On the other hand, all studied individuals of both species possessed the same internal transcribed spacer 2 haplotype. American specimens most probably originated from some western European populations. All studied specimens of P. tesselatus belong to the southwestern clade and western Mediterranean cluster. Therefore, together with cytological data, its species status is doubtful. To definitively solve the taxonomic status of P. tesselatus and populations of P. spumarius, further research using more samples and more genetic markers are needed.

Karyotypic characterization of three weevil species (Coleoptera: Curculionidae, Brachyderini).

Karyotypes of three species, Brachyderes incanus, Brachysomus setiger and Paophilus afflatus, belonging to the tribe Brachyderini, were studied using C-banding technique. The species share the same chromosome number 2n = 22 and meioformula n = 10+Xy(p) at all metaphase 1 plates of spermatid division. Some differences between karyotypes were observed in terms of centromere positions and C-band sizes. Most chromosomes are meta- or submetacentric and form a graded series in respect to length. The chromosomes resemble one another in having a rather small amount of heterochromatin restricted to the pericentromeric region and visible as dark stained blocks mainly during early stages of nuclear division. Only in Brachyderes incanus do larger bands occur at mitotic metaphase and diakinesis. These cytogenetic data are in agreement with karyological findings obtained in other species of Brachyderini so far examined.

Evidence of B-chromosomes in the karyotype of Barypeithes pellucidus Boheman 1834 [Coleoptera, Curculionidae, Entiminae] from Central Europe

B-chromosomes were observed in spermatogonial mitotic metaphases, meiotic metaphases I and II of Barpeithes pellucidus from one population in Slovakia. The number of B-chromosomes ranged from one to six per cell and they paired with the sex heterochromosomes in the first meiotic metaphase and rarely with the autosomes. In metaphase I one B-chromosome was always associated with X chromosome forming a tripartite complex. The XyBp was easily recognizable as a complex of three chromosomes in a parachute association The size of the B-chromosomes was approximately the same or a little smaller than that of the y heterochromosome which was the smallest element of the regular chromosome set. Their staining intensity seems to be similar to that of the autosomes and sex chromosomes, respectively. The behaviour of B-chromosomes during mitosis and meiosis in weevils is briefly discussed.

New cytogenetic data on Armenian buprestids (Coleoptera, Buprestidae) with a discussion of karyotype variation within the family.

As a part of ongoing cytogenetic studies on the jewel-beetles (Buprestidae, Coleoptera) of Armenia, the male karyotypes and meiosis of nine species (5 genera, 4 tribes, 2 subfamilies) are described, figured and discussed. In Ovalisia nadezhdae Sem., Sphenoptera artemisiae Reitt., Coraebus rubi L., C. sinuatus Creutz., Meliboeus caucasicus Reitt., Agrilus angustulus Ill. Men., A. obscuricollis Kiesw., and A. araxenus Khnz. diploid chromosome numbers vary in a narrow range from 20 to 24. In Sph. glabrata Men. a high chromosome number of 2n=40 was discovered. All the species have a XY sex chromosome system, which is however of different types. The data available on the buprestid karyotypes and karyotype variation at different taxonomic levels within the family are discussed.