Data from: Phenotypic and genetic integration of personality and growth under competition in the sheepshead swordtail, Xiphophorus birchmanni

Competition for resources including food, physical space, and potential mates is a fundamental ecological process shaping variation in individual phenotype and fitness. The evolution of competitive ability, in particular social dominance, depends on genetic (co)variation among traits causal (e.g., behaviour) or consequent (e.g. growth) to competitive outcomes. If dominance is heritable, it will generate both direct and indirect genetic effects (IGE) on resource dependent traits. The latter are expected to impose evolutionary constraint because winners necessarily gain resources at the expense of losers. We varied competition in a population of sheepshead swordtails, Xiphophorus birchmanni, to investigate effects on behaviour, size, growth, and survival. We then applied quantitative genetic analyses to determine (i) whether competition leads to phenotypic and/or genetic integration of behaviour with life history and (ii) the potential for IGE to constrain life history evolution. Size, growth and survival were reduced at high competition. Male dominance was repeatable and dominant individuals show higher growth and survival. Additive genetic contributions to phenotypic covariance were significant, with the G matrix largely recapitulating phenotypic relationships. Social dominance has a low but significant heritability and is strongly genetically correlated with size and growth. Assuming causal dependence of growth on dominance, hidden IGE will therefore reduce evolutionary potential.

包括食物、栖息空间与潜在配偶在内的资源竞争，是塑造个体表型（phenotype）与适合度（fitness）变异的基础性生态过程。竞争能力，尤其是社会支配地位（social dominance），的演化，取决于对竞争结果具有因果作用（如行为）或继发影响（如生长）的各类性状间的遗传（共）变异。若社会支配地位具有可遗传性，则会对资源依赖型性状（resource dependent traits）产生直接遗传效应（direct genetic effects）与间接遗传效应（indirect genetic effects, IGE）。后者预计将施加演化约束，因为优势个体获取资源必然以牺牲劣势个体为代价。我们在羊头剑尾鱼（Xiphophorus birchmanni）种群中调控竞争强度，以探究其对行为、体型、生长与存活的影响。随后我们开展数量遗传学分析（quantitative genetic analyses），以解答两大科学问题：其一，竞争是否会促使行为与生活史（life history）性状产生表型乃至遗传整合；其二，间接遗传效应制约生活史演化的潜在可能性。高竞争强度下，个体的体型、生长速率与存活率均显著下降。雄性的社会支配地位具有可重复性，优势个体展现出更高的生长速率与存活率。加性遗传对表型协方差（phenotypic covariance）的贡献显著，且G矩阵（G matrix）大体复现了表型性状间的关联模式。社会支配地位的遗传力（heritability）较低但显著，且与体型、生长存在较强的遗传相关。若假设生长对社会支配地位存在因果依赖，则隐性的间接遗传效应（IGE）将会降低种群的演化潜能。