Data from: It is lonely at the front: contrasting evolutionary trajectories in male and female invaders

Invasive species often exhibit rapid evolutionary changes, and can provide powerful insights into the selective forces shaping phenotypic traits that influence dispersal rates and/or sexual interactions. Invasions also may modify sexual dimorphism. We measured relative lengths of forelimbs and hindlimbs of more than 3000 field-caught adult cane toads (Rhinella marina) from 67 sites in Hawai'i and Australia (1–80 years post-colonization), along with 489 captive-bred individuals from multiple Australian sites raised in a ‘common garden’ (to examine heritability and reduce environmental influences on morphology). As cane toads spread from east to west across Australia, the ancestral condition (long limbs, especially in males) was modified. Limb length relative to body size was first reduced (perhaps owing to natural selection on locomotor ability), but then increased again (perhaps owing to spatial sorting) in the invasion vanguard. In contrast, the sex disparity in relative limb length has progressively decreased during the toads' Australian invasion. Offspring reared in a common environment exhibited similar geographical divergences in morphology as did wild-caught animals, suggesting a genetic basis to the changes. Limb dimensions showed significant heritability (2–17%), consistent with the possibility of an evolved response. Cane toad populations thus have undergone a major shift in sexual dimorphism in relative limb lengths during their brief (81 years) spread through tropical Australia.

入侵物种通常会表现出快速的演化变化，且可为解析塑造影响扩散速率或性互作的表型性状的选择压力提供强有力的研究视角。生物入侵过程同样可能改变性二态性（sexual dimorphism）。本研究测量了采自夏威夷与澳大利亚共67个采样点的3000余只野外捕获的成年海蟾蜍（Rhinella marina）成体的前后肢相对长度，这些样本的采集时间对应其种群定殖后的1至80年；同时还测量了来自多个澳大利亚原生采样点、于共同花园（common garden）环境下繁育的489只人工圈养个体的相关指标，以探究性状的遗传力并降低环境对形态的影响。随着海蟾蜍从东向西横跨澳大利亚扩散，其祖先种群的肢体相对长度特征（尤其是雄性肢体偏长的原始状态）发生了改变。相对于体体长的肢体长度，在入侵前沿种群中首先出现了下降（可能源于对运动能力的自然选择），随后又再度上升（可能源于空间分选作用）。与之形成对比的是，在海蟾蜍入侵澳大利亚的过程中，前后肢相对长度的性别差异逐步缩小。在共同花园环境中繁育的后代，其形态的地理分化模式与野生捕获个体高度相似，表明这些形态变化存在遗传基础。肢体尺寸性状表现出显著的遗传力（2%~17%），这与演化响应的可能性相符。因此，在短短81年的热带澳大利亚扩散过程中，海蟾蜍种群的相对肢体长度性二态性已发生了显著改变。