Sex change and the genetic structure of marine fish populations

Abstract

Sex change and the genetic structure of marine fish populations" (2009 Introduction 330Factors affecting population structure in marine fish 330Effective population size and sex change 331 Materials and methods 332Data collection 332 Data analysis 333Results 334Effect of sampling effort and species dispersal ability 334Testing the hypothesis: do sex-changing species show higher F ST ? 335Discussion 335Acknowledgements 339References 339 AbstractThe interaction between environmental forces and dispersal characteristics is largely responsible for the patterns of population structure in marine fish. Yet, crucial gaps in knowledge on life-histories and the relative contributions of numerous environmental factors still hinder a thorough understanding of marine population connectivity. One life-history trait so far overlooked by most fish population geneticists is sequential hermaphroditism, whereby individuals first mature as one sex and later in life reverse into the other sex. Population genetic theory predicts that sex-changing fish will present a higher potential for more spatially structured populations than gonochoristic species, as a result of their naturally skewed sex ratio, which is expected to reduce effective population size and hence increase genetic drift. We gathered published data on genetic population structure in marine fish, as summarized by the popular F ST index, and -after controlling for several potentially confounding factors -we tested the hypothesis that sex-changing species are more genetically structured than gonochoristic ones. Although we found no evidence to support the theoretical expectations, our results suggest new working hypotheses that can stimulate new research avenues at the intersection between physiology, genetics and fisheries science.

Stock structure of the blue threadfin (Eleutheronema tetradactylum) across northern Australia derived from life-history characteristics

“…A major goal of modern fisheries research is to acquire knowledge on spatial and temporal variation in demographics, to provide information on stock subdivision, genetic depletion, and the capacity of populations to cope with environmental changes (Chopelet et al, 2009;Palsbøll et al, 2007;Schwartz et al, 2007). As well as the life-history characteristics, the identification of the stock structure of exploited fish species is fundamental to fisheries management and provides the basis for the determination of appropriate spatial management units (Begg and Waldman, 1999).…”

Exploring neutral and adaptive processes in expanding populations of gilthead sea bream, Sparus aurata L., in the North-East Atlantic

“…Estimates of effective population size recorded at FRA, POR and SPA suggest the existence of large breeding populations, which contrasts with IRE, for which N e^w as finite and very small (32.6). Reduced effective population size can affect population structure by increasing the speed of random genetic drift, although very strong signals of genetic drift are typically rare in marine fish (Chopelet et al, 2009). Given the low, yet significant, F ST level detected, it would seem that genetic drift in the Irish population is nearly balanced out by significant immigration rate from southern locations (Davis, 1988;Fahy et al, 2005); otherwise, with N e o100, F ST values greater than 0.01 would build up after a couple of generations (Hedrick, 2000).…”

Sex change and effective population size: implications for population genetic studies in marine fish

“…Sex-change and genetic estimates of N e I Coscia et al All methods to calculate effective population size will assume discrete generations; therefore, underestimation of N e may occur here, but will likely affect both species similarly (Waples et al, 2014). Predictions from population genetics theory led to the expectation that a sex changing species would present smaller N e than a gonochoristic one for the following reasons: (a) the sex ratio of the sex-changing species is biased towards the 'first sex', which is known to reduce N e (Wright, 1931;Chopelet et al, 2009b); and (b) the dynamic balance of age-at-sex change, which affects individual variance in reproductive success (V k ). Using the LD method, we find agreement with these expectations, with substantially lower effective sizes in the protogynous C. puniceus; while N e estimates in C. nufar were one order or magnitude larger, with infinite upper confidence boundaries, indicating that more precise estimates in this species would ideally require greater sample sizes (Palstra and Ruzzante, 2008).…”