Autosomal differences between males and females in hybrid zones: a first report from Barbus barbus and Barbus meridionalis (Cyprinidae)

Abstract

International audienceNarrow hybrid zones are generally subjected to the action of two forces: dispersal, which tends to homogenise the hybridising taxa, and selection against hybrids, which, in contrast, produces steep clines of introgression for diagnostic markers. Although differences between sexes in dispersal abilities or in susceptibility to hybrid counterselection are common in hybrid zones, autosomal genetic differences between males and females have never been reported to our knowledge. Barbus barbus and Barbus meridionalis (Cyprinidae) form a hybrid zone along the Lergue river. By carrying out a genetic analysis of males and females in six samples from two central stations of the hybrid zone using codominant markers (six allozymes and four microsatellite loci), we revealed significant multilocus and monolocus differences between the sexes. This could reflect a genetic difference among sexes within a same cohort, caused either by a survival (or fertility) differential among sexes or by a sex-specific pattern of dispersal. Alternatively, this may be due to genetic differentiation between cohorts, since male and female barbel exhibit different maturation, growth and survival patterns leading to different age distributions among sexes, and particularly among reproducers

Introgressive hybridization between two Iberian endemic cyprinid fish: a comparison between two independent hybrid zones

“…On another hand, in the Caima zone, all backcross hybrids were in the direction of A. oligolepis , whereas mtDNA of both species was found in virtually the same proportions among A. oligolepis / A. oligolepis ‐like and P. duriense / P. duriense ‐like individuals. In general, these asymmetries in hybrid zones are considered to be the consequences of intrinsic attributes of the whole species that rarely or never depend on the geographical set‐up such as partial hybrid sterility, biased survival of hybrids (Chenouil et al. , 2004) or biased assortative mating and sexual selection (Meyer et al.…”

Sex-specific population structure, natural selection, and linkage disequilibrium in a wild bird population as revealed by genome-wide microsatellite analyses

“…The observed genetic differentiation between males and females was unexpected given that males and females are from the same cohorts and share genealogies within the pedigrees: their autosomal markers are mixed at each generation. Therefore, long-term evolutionary forces such as genetic drift or mutation could not generate autosomal genetic difference between sexes [29]. Moreover, selective effects were rarely (4/101, 3.97%) detected in the autosomal microsatellites.…”

“…The significant positive F IS observed in males is consistent with this argument as well. Alternative explanations for the sex-specific genetic differentiation would be differential viability, lifespan or hatching rate between sexes, which can lead to the allele frequency difference between females and males detected by F ST (see [8,29]). Unfortunately, given the available data in the Siberian jays, ascertaining the assumptions and quantifying the relevant parameters underlying these non-mutually exclusive hypotheses is difficult.…”

Intrinsic and extrinsic factors act at different spatial and temporal scales to shape population structure, distribution and speciation in Italian Barbus (Osteichthyes: Cyprinidae)

“…Previous studies have also indicated a preponderance of the larger species acting as the maternal donor (Chenuil et al, 2004;Lajbner et al, 2009;Meraner et al, 2013).…”