Ecological divergence and sexual selection drive sexual size dimorphism in new world pitvipers (Serpentes: Viperidae)

Hypotheses for the origin and maintenance of sexual size dimorphism (SSD) fall into three primary categories: (i) sexual selection on male size, (ii) fecundity selection on female size and (iii) ecological selection for gender-specific niche divergence. We investigate the impact of these forces on SSD evolution in New World pitvipers (Crotalinae). We constructed a phylogeny from up to eight genes (seven mitochondrial, one nuclear) for 104 species of NW crotalines. We gathered morphological and ecological data for 82 species for comparative analyses. There is a strong signal of sexual selection on male size driving SSD, but less evidence for fecundity selection on female size across lineages. No support was found for allometric scaling of SSD (Rensch's rule), nor for directional selection for increasing male size (the Fairbairn–Preziosi hypothesis) in NW crotalines. Interestingly, arboreal lineages experience higher rates of SSD evolution and a pronounced shift to female-biased dimorphis...

关于性别大小二态性（sexual size dimorphism, SSD）的起源与维持假说可归纳为三大类别：(i) 针对雄性体型的性选择、(ii) 针对雌性体型的繁殖力选择，以及(iii) 基于性别特异性生态位分化的生态选择。本研究针对新大陆蝮亚科（Crotalinae）蛇类，探讨了上述演化压力对其性别大小二态性演化的影响。我们基于104种新大陆蝮亚科蛇类的至多8个基因（7个线粒体基因、1个核基因）构建了系统发育树；同时收集了其中82个物种的形态学与生态学数据用于比较分析。研究结果显示，雄性体型所受的性选择是驱动性别大小二态性演化的强信号，但各支系中雌性体型受繁殖力选择的支持证据相对不足。本研究未发现支持新大陆蝮亚科蛇类性别大小二态性异速生长缩放（伦施法则，Rensch's rule）的证据，亦未发现支持雄性体型增大定向选择（费尔贝恩-普雷佐西假说，Fairbairn–Preziosi hypothesis）的证据。值得注意的是，树栖支系的性别大小二态性演化速率更高，且显著向雌性偏态的二态性模式转变……