Reproductive isolation due to prezygotic isolation and postzygotic cytoplasmic incompatibility in parasitoid wasps

Abstract

The reproductive barriers that prevent gene flow between closely related species are a major topic in evolutionary research. Insect clades with parasitoid lifestyle are among the most species‐rich insects and new species are constantly described, indicating that speciation occurs frequently in this group. However, there are only very few studies on speciation in parasitoids. We studied reproductive barriers in two lineages of Lariophagus distinguendus (Chalcidoidea: Hymenoptera), a parasitoid wasp of pest beetle larvae that occur in human environments. One of the two lineages occurs in households preferably attacking larvae of the drugstore beetle Stegobium paniceum (“DB‐lineage”), the other in grain stores with larvae of the granary weevil Sitophilus granarius as main host (“GW‐lineage”). Between two populations of the DB‐lineage, we identified slight sexual isolation as intraspecific barrier. Between populations from both lineages, we found almost complete sexual isolation caused by female mate choice, and postzygotic isolation, which is partially caused by cytoplasmic incompatibility induced by so far undescribed endosymbionts which are not Wolbachia or Cardinium. Because separation between the two lineages is almost complete, they should be considered as separate species according to the biological species concept. This demonstrates that cryptic species within parasitoid Hymenoptera also occur in Central Europe in close contact to humans.

Symbiont-mediated cytoplasmic incompatibility: What have we learned in 50 years?

“…Aside from Wolbachia , the far less common ( Weinert et al, 2015 ; Zchori-Fein and Perlman, 2004 ) Bacteroidetes bacteria Cardinium were found to cause CI nearly three decades later ( Hunter et al, 2003 ; Yen and Barr, 1973 ). Additionally, unknown symbionts of Brontispa longissimi coconut beetles and Lariophagus distinguendus parasitoid wasps cause CI, but they are not Wolbachia or Cardinium ( König et al, 2019 ; Takano et al, 2017 ). In addition, Gammaproteobacteria of the genus Rickettsiella cause CI in Mermessus fradeorum spiders ( Rosenwald et al, 2020 ).…”

A Role for Maternal Factors in Suppressing Cytoplasmic Incompatibility

“…Fundamental to these questions is whether a core set of maternal mechanisms in insects can act to suppress CI across systems. Fortunately, the framework presented here enables broad investigation of diverse CI-Rescue systems in the future, including that of non-Wolbachia endosymbionts like Cardinium (Hunter et al, 2003;Penz et al, 2012;Mann et al, 2017;Takano et al, 2017;König et al, 2019;Doremus and Hunter, 2020).…”

“…Cardinium endosymbionts carried by Encarsia wasps have been credited with inducing their own forms of CI and Rescue (Hunter et al, 2003;Penz et al, 2012;Mann et al, 2017), in the apparent absence of Cif proteins altogether (Lindsey et al, 2018;Doremus and Hunter, 2020). Two additional non-Wolbachia CI systems were recently identified (Doremus and Hunter, 2020), in Lariophagus wasps (König et al, 2019) as well as in Brontispa beetles (Takano et al, 2017). While it is possible that each endosymbiont has a self-contained mechanism for CI and Rescue, another possibility is that these functionally convergent phenotypes are due to endosymbiont effects on conserved, cellular processes of the host.…”

Symbiont-Mediated Cytoplasmic Incompatibility: What have we Learned in 50 Years?

“…Aside from Wolbachia, the far less common (Weinert et al, 2015;Zchori-Fein and Perlman, 2004) Bacteroidetes bacteria Cardinium were found to cause CI nearly three decades later (Hunter et al, 2003;Yen and Barr, 1973). Additionally, unknown symbionts of Brontispa longissimi coconut beetles and Lariophagus distinguendus parasitoid wasps cause CI, but they are not Wolbachia or Cardinium (König et al, 2019;Takano et al, 2017). In addition, Rickettsiella Gammaproteobacteria cause CI in Mermessus fradeorum spiders (Rosenwald et al, 2020).…”