Aubin-Horth Nadia, Dodson Julian J
Centre Interuniversitaire de Recherche sur le Saumon Atlantique, Département de Biologie, Université Laval, Cité Universitaire, Quebec, Quebec G1K 7P4, Canada.
Evolution. 2004 Jan;58(1):136-44. doi: 10.1111/j.0014-3820.2004.tb01580.x.
In the conditional strategy model, divergence in reproductive phenotypes depends on whether the individual's condition is above or below a genetically determined threshold. The relative contribution of the genetic and environmental components that lead to the expression of a reproductive tactic by an individual is not well understood. In the present field study, we determined when condition diverged between males that develop the mature parr phenotype and those that do not in Atlantic salmon (Salmo salar). We also investigated the uniformity of the threshold value in the population. We sampled mature parr and immature males at age one, of the same population at six different sites for four consecutive years. Our study provides an example of the interaction of genotype and environment on the expression of a reproductive tactic. Size was significantly greater for future mature parr than for future immature males as early as 20 days after hatching (emergence), suggesting that there may be a parental effect component in the tactic adopted, since no exogenous feeding takes place before this time. Size advantage at emergence was maintained through the next spring at age one to different degrees depending on the year, thus suggesting the presence of an environmental component of tactic expression. Our results support the contention that within the conditional strategy, the environment faced by a male and his condition at the moment of reproduction consistently predicts neither the environment faced by his offspring nor the fitness they will obtain by expressing the same tactic as their father. Furthermore, higher mean size at a site did not always translate into a higher proportion of mature parr, therefore supporting the hypothesis that thresholds vary across habitats within the same population.
在条件策略模型中，繁殖表型的差异取决于个体状况是高于还是低于基因决定的阈值。导致个体表达某种繁殖策略的遗传和环境成分的相对贡献尚未得到充分理解。在本实地研究中，我们确定了在大西洋鲑（Salmo salar）中，发育成熟幼鲑表型的雄性与未发育成熟幼鲑表型的雄性之间，状况何时出现差异。我们还研究了种群中阈值的一致性。我们连续四年在六个不同地点对同一种群一岁的成熟幼鲑和未成熟雄性进行采样。我们的研究提供了一个基因型与环境相互作用影响繁殖策略表达的例子。早在孵化（出膜）后20天，未来的成熟幼鲑的体型就显著大于未来的未成熟雄性，这表明所采用的策略中可能存在亲代效应成分，因为在此之前没有进行外源投喂。出膜时的体型优势在一岁的次年春季不同程度地得以保持，这表明策略表达存在环境成分。我们的结果支持这样的观点，即在条件策略中，雄性在繁殖时所面临的环境及其状况并不能始终预测其后代所面临的环境，也不能预测它们通过表达与其父亲相同的策略所获得的适合度。此外，一个地点的平均体型较大并不总是转化为成熟幼鲑的比例较高，因此支持了同一物种内不同栖息地阈值不同的假设。
