Incomplete offspring sex bias in Australian populations of the butterfly Eurema hecabe

Abstract

Theory predicts unified sex ratios for most organisms, yet biases may be engendered by selfish genetic elements such as endosymbionts that kill or feminize individuals with male genotypes. Although rare, feminization is established for Wolbachiainfected Eurema butterflies. This paradigm is presently confined to islands in the southern Japanese archipelago, where feminized phenotypes produce viable all-daughter broods. Here, we characterize sex bias for E. hecabe in continental Australia. Starting with 186 wild-caught females, we reared 46000 F1-F3 progeny in pedigree designs that incorporated selective antibiotic treatments. F1 generations expressed a consistent bias across 2 years and populations that was driven by an~5% incidence of broods comprising ⩾ 80% daughters. Females from biased lineages continued to overproduce daughters over two generations of outcrossing to wild males. Treatment with antibiotics of differential strength influenced sex ratio only in biased lineages by inducing an equivalent incomplete degree of son overproduction. Brood sex ratios were nevertheless highly variable within lineages and across generations. Intriguingly, the cytogenetic signature of female karyotype was uniformly absent, even among phenotypic females in unbiased lineages. Molecular evidence supported the existence of a single Wolbachia strain at high prevalence, yet this was not clearly linked to brood sex bias. In sum, we establish an inherited, experimentally reversible tendency for incomplete offspring bias. Key features of our findings clearly depart from the Japanese feminization paradigm and highlight the potential for more subtle degrees of sex distortion in arthropods.

Genotype‐environment interaction reveals varied developmental responses to unpredictable host phenology in a tropical insect

“…Procedures for mating individuals in the laboratory (which are incidental to this study) were as outlined by Kemp et al. (2017). All generations and life stages were housed in the same controlled laboratory environment, which was set to standard conditions for this species of 26 ± 1°C, 14 h daylength, and relative humidity of 55–65%.…”

“…Second instar larvae were transferred to a fresh cutting of their designated treatment host and thereafter reared individually in 750 ml plastic cups (as detailed and illustrated by Kemp et al. 2017). Each cup was labeled with a unique specimen identifier such that genetic lineage was not evident during husbandry activities.…”

Μελέτη Κοινοτήτων Συμβιωτικών Βακτηρίων Σε Έντομα Αγροτικής Και Περιβαλλοντικής Σημασίας

“…Μία περίπτωση ατελούς θηλυκοποίησης παρατηρήθηκε σε πληθυσμούς του Eurema hecabe από την Αυστραλία, όπου παράγονταν θηλυκοί και αρσενικοί απόγονοι σε αναλογία περίπου 2:1, η οποία αντιστρέφονταν με την χρήση αντιβιοτικού. Τελικά στα άτομα βρέθηκε ένα στέλεχος Wolbachia, το wCI ενώ κανένας θηλυκός απόγονος δεν είχε τον γονότυπο ZW(Kemp et al, 2017).Δ. Θηλυτόκος παρθενογένεσηΓενικά, σαν παρθενογένεση χαρακτηρίζεται η παραγωγή απογόνων από θηλυκά άτομα χωρίς να έχει προηγηθεί γονιμοποίηση από αρσενικά(Werren et al, 2008) (Εικόνα 1.18).…”