Zimmermann Tobias D, Kaiser Sylvia, Hennessy Michael B, Sachser Norbert
Department of Behavioural Biology, University of Münster, 48149 Münster, Germany
Münster Graduate School of Evolution, University of Münster, 48149 Münster, Germany.
Proc Biol Sci. 2017 Feb 22;284(1849). doi: 10.1098/rspb.2016.2784.
Environmental conditions during early life can adaptively shape the phenotype for the prevailing environment. Recently, it has been suggested that adolescence represents an additional temporal window for adaptive developmental plasticity, though supporting evidence is scarce. Previous work has shown that male guinea pigs living in large mixed-sex colonies develop a low-aggressive phenotype as part of a queuing strategy that is adaptive for integrating into large unfamiliar colonies. By contrast, males living in pairs during adolescence become highly aggressive towards strangers. Here, we tested whether the high-aggressive phenotype is adaptive under conditions of low population density, namely when directly competing with a single opponent for access to females. For that purpose, we established groups of one pair-housed male (PM), one colony-housed male (CM) and two females. PMs directed more aggression towards the male competitor and more courtship and mating towards females than did CMs. In consequence, PMs attained the dominant position in most cases and sired significantly more offspring. Moreover, they showed distinctly higher testosterone concentrations and elevated cortisol levels, which probably promoted enhanced aggressiveness while mobilizing necessary energy. Taken together, our results provide the clearest evidence to date for adaptive shaping of the phenotype by environmental influences during adolescence.
生命早期的环境条件能够适应性地塑造适合当前环境的表型。最近,有人提出青春期是适应性发育可塑性的另一个时间窗口,不过相关证据稀少。此前的研究表明,生活在大型混合性别群体中的雄性豚鼠会形成低攻击性的表型,这是一种排队策略的一部分,有助于融入大型陌生群体。相比之下,青春期成对生活的雄性豚鼠对陌生个体极具攻击性。在此,我们测试了在低种群密度条件下,即与单个对手直接竞争获取雌性机会时,高攻击性表型是否具有适应性。为此,我们组建了由一只成对饲养的雄性豚鼠(PM)、一只群体饲养的雄性豚鼠(CM)和两只雌性豚鼠组成的组。与CM相比,PM对雄性竞争者表现出更多攻击性,对雌性表现出更多求偶行为和交配行为。结果,在大多数情况下,PM占据主导地位,且生育的后代显著更多。此外,它们的睾酮浓度明显更高,皮质醇水平也有所升高,这可能在调动必要能量的同时促进了攻击性增强。综上所述,我们的研究结果为青春期环境影响对表型的适应性塑造提供了迄今为止最清晰的证据。