Symbionts do not affect the mating incompatibility between the Brazilian-1 and Peruvian morphotypes of the Anastrepha fraterculus cryptic species complex

Abstract

The South American fruit fly, Anastrepha fraterculus, is clearly undergoing a speciation process. Among others, two of their morphotypes, the Brazilian-1 and Peruvian, have accumulated differences in pre- and post-zygotic mechanisms resulting in a degree of reproductive isolation. Both harbor a different strain of Wolbachia, which is a widespread endosymbiotic bacterium among many invertebrates producing a range of reproductive effects. In this paper, we studied the role of this bacterium as one of the factors involved in such isolation process. Infected and cured laboratory colonies were used to test pre- and post-zygotic effects, with special emphasis in uni- and bi-directional cytoplasmic incompatibility (CI). We showed that Wolbachia is the only known reproductive symbiont present in these morphotypes. Wolbachia reduced the ability for embryonic development in crosses involving cured females and infected males within each morphotype (uni-directional CI). This inhibition showed to be more effective in the Peruvian morphotype. Bi-directional CI was not evidenced, suggesting the presence of compatible Wolbachia strains. We conclude that Wolbachia is not directly involved in the speciation process of these morphotypes. Other mechanisms rather than CI should be explored in order to explain the reduced mating compatibility between the Brazilian-1 and Peruvian morphotypes.

Wolbachia pipientis Associated With Tephritid Fruit Fly Pests: From Basic Research to Applications

“…Based mostly on PCR and sequencing approaches, ∼66% of ∼87 tephritid species screened have at least one record of positive Wolbachia infection (excluding pseudogenes) in laboratory and natural populations (see Supplementary File S1; only supergroups A and B have been found in tephritids). For the genus Anastrepha, all but one species (Anastrepha ludens) of 17 screened to date harbor Wolbachia (Werren et al, 1995;and this study;Selivon et al, 2002;Coscrato et al, 2009;Martínez et al, 2012;Mascarenhas et al, 2016;Morán-Aceves, 2016;Prezotto et al, 2017;Conte et al, 2019;Devescovi et al, 2019). Most Anastrepha species harbor Wolbachia strains assigned to supergroup A. Anastrepha striata Schiner and Anastrepha serpentina (Wiedemann), however, harbor supergroup B in southern Mexico (Martínez et al, 2012;and H. Martinez and M. Mateos, pers.…”

“…1"). No evidence of bidirectional CI was detected in the crosses between the two morphotypes, leading Devescovi et al (2019) to conclude that Wolbachia is not directly involved in the speciation process of these morphotypes. Ribeiro (2009) reported evidence consistent with CI caused by Wolbachia in A. obliqua and in "A. fraterculus sp.…”

“…However, the same work described the presence of slightly detrimental effects on larval survival and a female-biased sex ratio, suggesting the induction of malekilling phenomena. Moreover, Devescovi et al (2019) found that Wolbachia reduced the embryo hatching in crosses involving cured females and infected males (uni-directional CI) within two morphotypes of this cryptic species complex; stronger CI was detected within the Peruvian morphotype than the Brazilian-1 morphotype (also referred as to "A. fraterculus sp. 1").…”

“…Even intensely studied groups in terms of heritable symbionts, such as tsetse flies (genus Glossina), can yield surprises of bacterial associates (e.g., the recent discovery of Spiroplasma in two species of Glossina; Doudoumis et al, 2017). With few exceptions (Martínez et al, 2012;Augustinos et al, 2015;Asimakis et al, 2019;Conte et al, 2019;Devescovi et al, 2019), research on tephritid facultative heritable bacteria has not examined the possibility of players other than Wolbachia. Therefore, we urge that such research include screens for other symbionts, including viruses, protozoans, and fungi.…”

Gut Bacteriome Analysis of Anastrepha fraterculus sp. 1 During the Early Steps of Laboratory Colonization

“…The most abundant genera, were Wolbachia (Alphaproteobacteria) and Enterobacter (Gammaproteobacteria), followed by other members of the Gammaproteobacteria such as Providencia, Aeromonas, Citrobacter, Burkholderia-Caballeronia-Paraburkholderia, Klebsiella and Raoultella. Tephritid literature reports these genera of Proteobacteria with specific functions: Wolbachia with cytoplasmic incompatibility and male killing (Boller and Bush, 1974;Riegler and Stauffer, 2002;Zabalou et al, 2004Zabalou et al, , 2009Apostolaki et al, 2011;Conte et al, 2019;Devescovi et al, 2019;Mateos et al, 2020), Enterobacter, Citrobacter, Burkholderia, Klebsiella and Raoultella with nitrogen metabolism (Murphy et al, 1988;Behar et al, 2005;Raza et al, 2020), and Providencia with pathogenic effects (Msaad Guerfali et al, 2018;Ksentini et al, 2019). In addition, Acinetobacter and Rheinheimera (Gammaproteobacteria) were detected in low abundance (0,1% of total reads) but in a high percentage of samples (33.33 and 46.97% of total samples, respectively) and wide distribution (Lab, WU, F0, F1-F6 flies).…”