Demographic and genetic consequences of disturbed sex determination

Abstract

During sex determination, genetic and/or environmental factors determine the cascade of processes of gonad development. Many organisms, therefore, have a developmental window in which their sex determination can be sensitive to, for example, unusual temperatures or chemical pollutants. Disturbed environments can distort population sex ratios and may even cause sex reversal in species with genetic sex determination. The resulting genotype-phenotype mismatches can have long-lasting effects on population demography and genetics. I review the theoretical and empirical work in this context and explore in a simple population model the role of the fitness of chromosomally aberrant YY genotypes that are a consequence of environmentally induced feminization. Low is mostly beneficial for population growth. During feminization, low reduces the proportion of genetic males and hence accelerates population growth, especially at low rates of feminization and at high fitness costs of the feminization itself (i.e. when feminization would otherwise not affect population dynamics much). When sex reversal ceases, low mitigates the negative effects of feminization and can even prevent population extinction. Little is known about in natural populations. The available models now need to be parametrized in order to better predict the long-term consequences of disturbed sex determination.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.

Adult sex ratios and reproductive strategies: a critical re-examination of sex differences in human and animal societies

“…Many animal species too are experiencing dramatic swings in ASRs. For example, climate change and pollution have been shown to alter the relative number of males to females in species with temperature-sensitive sex-determination and/or those that experience impediments to development in response to environmental contaminants [61,62]. Accordingly, studies of species conservation raise the concern that population-level viability is declining in response to uncertain environments.…”

“…Using a theoretical model and empirical examples, Wedekind [61] explores the consequences of disturbed environments for population sex ratios. He argues that environmentally driven feminization could be more common than currently thought, although the frequency of these phenotype-genotype mismatched individuals may significantly affect population dynamics.…”

Sex differentiation in grayling (Salmonidae) goes through an all-male stage and is delayed in genetic males who instead grow faster

“…It is important to understand sex determination and sex differentiation especially in fish that play key roles in their respective environment 42 , that are, or could potentially be, important in aquaculture 13 , or that already suffer from distorted sex ratios as repeatedly observed in river-dwelling salmonids 43 . All of this is true for the European grayling, and especially for the population we study 21 .…”

Divergent density feedback control of migratory predator recovery following sex-biased perturbations

“…Sexual dimorphism, for example, is prevalent in natural populations (Fairbairn 1997), 54 often leading to sex-biased pressure (Coltman et al 2003). As stress becomes intensified, these 55 sources of intraspecific variation in fitness may emerge as a directional shift in demographic 56 rates (Wedekind 2017), diminishing reproductive output (Knell & Martínez-Ruiz 2017). Because 57 of sex-dependent differential investment in reproduction, sex-biased stresses may pose a 58 unpredictable threat to persistence of wild populations (Coltman et al 2003).…”