Post E, Langvatn R, Forchhammer M C, Stenseth N C
Department of Biology, Division of Zoology, University of Oslo, P.O. Box 1050 Blindern, N-0316 Oslo, Norway.
Proc Natl Acad Sci U S A. 1999 Apr 13;96(8):4467-71. doi: 10.1073/pnas.96.8.4467.
Sexual dimorphism results from dichotomous selection on male and female strategies of growth in relation to reproduction. In polygynous mammals, these strategies reflect sexual selection on males for access to females and competitive selection on females for access to food. Consequently, in such species, males display rapid early growth to large adult size, whereas females invest in condition and early sexual maturity at the expense of size. Hence, the magnitude of adult size dimorphism should be susceptible to divergence of the sexes in response to environmental factors differentially influencing their growth to reproduction. We show that divergent growth of male and female red deer after 32 years of winter warming and 15 years of contemporaneously earlier plant phenology support this prediction. In response to warmer climate during their early development, males grew more rapidly and increased in size, while female size declined. Conversely, females, but not males, responded to earlier plant phenology with increased investment in condition and earlier reproduction. Accordingly, adult size dimorphism increased in relation to warmer climate, whereas it declined in relation to forage quality. Thus, the evolutionary trajectories of growth related to reproduction in the sexes (i) originate from sexual and competitive selection, (ii) produce sexual size dimorphism, and (iii) are molded by environmental variation.
两性异形源于对雄性和雌性与繁殖相关的生长策略的二分选择。在一夫多妻制的哺乳动物中，这些策略反映了对雄性获取雌性的性选择以及对雌性获取食物的竞争选择。因此，在这类物种中，雄性在早期快速生长至成年后的较大体型，而雌性则以牺牲体型为代价，投入到身体状况和早期性成熟方面。所以，成年体型的两性差异程度应该容易受到性别差异的影响，以应对不同地影响它们生长至繁殖过程的环境因素。我们表明，经过32年的冬季变暖以及同时出现的15年植物物候提前之后，雄性和雌性马鹿的生长差异支持了这一预测。在早期发育过程中，由于气候变暖，雄性生长得更快且体型增大，而雌性体型下降。相反，雌性（而非雄性）对植物物候提前的反应是增加对身体状况的投入和提前繁殖。相应地，成年体型的两性差异随着气候变暖而增大，而随着饲料质量下降而减小。因此，两性中与繁殖相关的生长进化轨迹：（i）源于性选择和竞争选择；（ii）产生两性体型差异；（iii）受到环境变化的塑造。
