A tale of swinger insects: Signatures of past sexuality between divergent lineages of a parthenogenetic weevil revealed by ribosomal intraindividual variation.

Marcela S Rodriguero,Josefina S Alberghina,Analía A Lanteri,Sonia A Wirth,Viviana A Confalonieri

doi:10.1371/journal.pone.0195551

Abstract

Naupactus cervinus (Boheman) (Curculionidae, Naupactini) is a parthenogenetic weevil native to the Paranaense Forest which displays high levels of genetic variation. Two divergent clades were identified, one ranging in forest areas (Forest clade), and the other in open vegetation areas (Grassland clade). Both of them have individuals with high levels of heterozygosity in ribosomal sequences. Investigation of intraindividual variation in ITS1 sequences through cloning and posterior sequencing suggested that mating between both groups most likely occurred in the Paranaense Forest after a secondary contact, which led to fixed heterozygotes as a consequence of parthenogenesis. Otherwise, sexual segregation would have disrupted multilocus genotypes. Only a small number of heterozygous genotypes of all the possible combinations are found in nature. We propose the occurrence of a hybrid zone in the Paranaense Forest. The fact that it is one of the most important biodiversity hotspots of the world, together with its key role for investigating evolutionary processes, makes it worthy of conservation. This is the first genetic evidence of bisexuality in N. cervinus.

Highlights

Weevils are unique for evolutionary entomologists because they show many interesting features such as parthenogenesis and polyploidy [1]
Our results can be explained by the occurrence of outcrossing between divergent lineages or mutations in paralogous copies of ITS1 coupled with incomplete concerted evolution
Multiple alignment of the whole set of ITS1 alleles known for N. cervinus with those obtained in the present work (i.e. 127 clones) and other ITS1 sequences from other Naupactus species yielded a matrix of 961 bp in length and showed 97 substitutions and ten deletions/ insertions

Summary

Introduction

Weevils are unique for evolutionary entomologists because they show many interesting features such as parthenogenesis and polyploidy [1]. In the Old World the genus Otiorhynchus (Entiminae, Otiorrhynchini) comprises more than 60 unisexual species distributed in Central and Northern Europe (e.g., [1,2,3,4,5]), where parthenogenetic species of the genus Polydrosus are found [6,7]. Several species of the genus Cathormiocerus inhabit the British and Azores Isles [8,9]. In Japan, about 10% of weevils are unisexual [10], and similar numbers were reported for Canada [11].

Methods

Results

Conclusion