Assessment of the role of Wolbachia in mtDNA paraphyly and the evolution of unisexuality in Calligrapha (Coleoptera: Chrysomelidae)

Abstract

Calligrapha is a New World leaf beetle genus that includes several unisexual species in northeastern North America. Each unisexual species had an independent hybrid origin involving different combinations of bisexual species. However, surprisingly, they all cluster in a single mtDNA clade and with some individuals of their parental species, which are in turn deeply polyphyletic for mtDNA. This pattern is suggestive of a selective sweep which, together with mtDNA taxonomic incongruence and occurrence of unisexuality in Calligrapha, led to hypothesize that Wolbachia might be responsible. I tested this hypothesis studying the correlation between diversity of Wolbachia and well‐established mtDNA lineages in >500 specimens of two bisexual species of Calligrapha and their derived unisexual species. Wolbachia appears highly prevalent (83.4%), and fifteen new supergroup‐A strains of the bacteria are characterized, belonging to three main classes: wCallA, occupying the whole species ranges, and wCallB and wCallC, narrowly parapatric, infecting beetles with highly divergent mtDNAs where they coexist. Most beetles (71.6%) carried double infections of wCallA with another sequence class. Bayesian inference of ancestral character states and association tests between bacterial diversity and the mtDNA genealogy show that each mtDNA lineage of Calligrapha has specific types of infection. Moreover, shifts can be explained by horizontal or vertical transfer from local populations to an expanding lineage and cytoplasmic incompatibility between wCallB and wCallC types, suggesting that the symbionts hitchhike with the host and are not responsible for selective mtDNA sweeps. Lack of evidence for sweeps and the fact that individuals in the unisexual clade are uninfected or infected by the widespread wCallA type indicate that Wolbachia does not induce unisexuality in Calligrapha, although they may manipulate host reproduction through cytoplasmic incompatibility.

Does diet breadth affect the complexity of the phytophagous insect microbiota? The case study of Chrysomelidae

“…For the majority of the analysed Chrysomelidae, the association with these bacteria is reported in this study for the first time. The presence of reproductive manipulators, such as Wolbachia , in Chrysomelidae is well known (Montagna et al ., 2014; Kajtoch and Kotásková, 2018; Gómez‐Zurita, 2019). These endosymbiotic bacteria are usually abundant in infected species, tending to dominate the community, as observed in this study for four Chrysomelidae species, where Wolbachia represent 94%–99% of the reads.…”

“…Previous studies on the bacteria associated to leaf beetles were mainly focused on reproductive manipulators (Clark et al ., 2001; Keller et al ., 2004; Kondo et al ., 2011; Roehrdanz and Wichmann, 2013; Montagna et al ., 2014; Krawczyk et al ., 2015; Kolasa et al ., 2017; Takano et al ., 2017; Gómez‐Zurita, 2019), single species of economic importance (Muratoglu et al ., 2011; Chung et al ., 2013; Ali et al ., 2019; Ludwick et al ., 2019; Wang et al ., 2019; Shukla and Beran, 2020) or few strictly related species (Kelley and Dobler, 2011; Montagna et al ., 2015a; Blankenchip et al ., 2018; Wei et al ., 2020). The present study aims to characterize the microbiota associated with a selection of leaf beetle species, representative of the taxonomic diversity and of the various degrees of trophic specialization.…”

Food Resource Sharing of Alder Leaf Beetle Specialists (Coleoptera: Chrysomelidae) as Potential Insect–Plant Interface for Horizontal Transmission of Endosymbionts

“…The rate of infection with Wolbachia in Coleoptera varies considerably, depending on the host taxonomy, with Chrysomelidae showing intermediate values ( Kajtoch and Kotásková 2017 ). However, our study precisely focused on two genera, Altica and Calligrapha , which have been shown to have particularly high infection rates with Wolbachia among the leaf beetle groups tested ( Jäckel et al 2013 , Gómez-Zurita 2019 ). Rickettsia has received much less attention than Wolbachia in studies of associations of bacteria with Coleoptera.…”

“…The latter is interesting, since it relates this finding with the other only study on Calligrapha endosymbionts, because we know that individuals of Ca. philadelphica in the locality of the study and in the general area are infected by two Wolbachia strains that were named wCalA1 and wCalC2 , with wCalA1 shared with at least three other species, two of them specialized on yet a different host plant, willows ( Gómez-Zurita 2019 ). These data are compatible with the hypothesis that host plants favor shared endosymbiont associations, suggesting a number of interesting ideas, worth testing with a more extensive study.…”