The Contributions of Premating and Postmating Selection Episodes to Total Selection in Sex-Role-Reversed Gulf Pipefish

Abstract

Empirical studies of sexual selection often focus on events occurring either before or after mating but rarely both and consequently may fail to discern the relative magnitudes and interactions of premating and postmating episodes of selection. Here, we simultaneously quantify premating and postmating selection in the sex-role-reversed Gulf pipefish by using a microsatellite-based analysis of parentage in experimental populations. Female pipefish exhibited an opportunity for selection (I) of 1.64, which was higher than that of males (0.35). Decompositions of I and the selection differential on body size showed that over 95% of the selection on females arose from the premating phase. We also found evidence for a trade-off between selection phases, where multiply mating females had significantly lower offspring survivorship compared to singly mated females. In males, variance in relative fitness arose mainly from the number of eggs received per copulation and a small number of males who failed to mate. Overall, our study exemplifies a general approach for the decomposition of total selection into premating and postmating phases to understand the interplay among components of natural and sexual selection that conspire to shape sexually selected traits.

Genome‐wide selection components analysis in a fish with male pregnancy

“…We expected to find a signature of selection because Gulf pipefish females are known to be under strong sexual selection (Jones et al 2001;Rose et al 2013;Flanagan et al 2014), and we did find higher F ST values in the mothers-females comparison than between males and females. We expected to find a signature of selection because Gulf pipefish females are known to be under strong sexual selection (Jones et al 2001;Rose et al 2013;Flanagan et al 2014), and we did find higher F ST values in the mothers-females comparison than between males and females.…”

“…However, we identified a much larger number of significant RAD loci in the males-females comparison than in the comparison of inferred maternal alleles and females. Since sexual selection is known to act on females and not males in S. scovelli (Rose et al 2013), a trade-off between traits could explain genome-wide allele frequency differences between the sexes. These results suggest that differential selection on males and females may be having a pervasive effect throughout the genome.…”

Sexual selection gradients change over time in a simultaneous hermaphrodite

“…In short-term experiments, and (imposed) semelparous situations, one can separate pre- from post-copulatory components of sexual selection by looking at the residual variance in reproductive success, i.e. the variance not explained by mating success (this residual can be explained by post-copulatory processes: Rose et al, 2013a, 2013b; Pélissié et al, 2014; Janicke et al, 2015). This is no longer straight-forward in a dataset from a longer running experiment where everyone has mated repeatedly with everyone else and sperm from those previous matings is still in storage.…”

“…So far, experiments were generally only performed over a short time frame, as pointed out earlier; e.g. Pélissié et al, 2012, Pélissié et al, 2014; Anthes et al, 2010; Collet et al, 2012; Rose et al, 2013a; but see Turnell and Shaw, 2015). …”

Female ornaments signal own and offspring quality in a sex‐role‐reversed fish with extreme male parental care

“…Oocyte size seems to be a good explanation for this preference, as wider stripes indicate larger oocytes, which are known to be more nutritious (Goncalves et al., ). Size is certainly another trait selected by syngnathid males (Berglund et al., , ; Mattle & Wilson, ; Paczolt & Jones, ; Rose, Paczolt, & Jones, ), including S. abaster (Silva et al., ), as it is usually positively related to female fecundity (Braga Goncalves et al., ). However, as we verified in S. abaster , size can at times be only indirectly related to female quality, both through stripe width and trunk broadness.…”