The Incidence of Wolbachia Bacterial Endosymbiont in Bisexual and Parthenogenetic Populations of the Psyllid Genus Cacopsylla (Hemiptera, Psylloidea)

Simple Summary: Wolbachia has many varied impacts on the biology and evolution of insects and some other groups of invertebrates. The number of studies that have particularly addressed the impact of Wolbachia infection on reproduction and processes of speciation and diversification of host species has grown rapidly over the past decade. Despite that, our current knowledge on Wolbachia is limited, and comprehensive large-scale biogeographical studies devoted to the incidence of Wolbachia within a certain taxon or groups of taxa, although they are of great importance, are still scarce. In the present study, we focused on several Palaearctic Cacopsylla (Hemiptera, Psylloidea) species with different (parthenogenetic and bisexual) reproductive strategies. We conducted PCR screening of 526 specimens collected in different geographical regions of Europe and Russia in order to estimate a broad pattern of Wolbachia incidence and prevalence of five Cacopsylla species, Cacopsylla. borealis, Cacopsylla. lapponica, Cacopsylla. myrtilli, Cacopsylla. ledi, and Cacopsylla. fraudatrix. We revealed significant differences in infection frequencies between the species and even distinct populations of the same species, which, however, did not correlate with reproduction strategy or gender. These findings provide a starting point for understanding the role of Wolbachia infection in Cacopsylla evolution and diversity. 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.

Automated summary

Wolbachia infection frequency varies significantly between different Cacopsylla species and populations, unrelated to reproductive strategy or gender. The findings suggest an essential role of Wolbachia in the evolution and diversity of Cacopsylla species.