Data from: Differences in developmental strategies between long-settled and invasion-front populations of the cane toad in Australia

Phenotypic plasticity can enhance a species’ ability to persist in a new and stressful environment, so that reaction norms are expected to evolve as organisms encounter novel environments. Biological invasions provide a robust system to investigate such changes. We measured the rates of early growth and development in tadpoles of invasive cane toads (Rhinella marina) in Australia, from a range of locations and at different larval densities. Populations in long-colonized areas have had the opportunity to adapt to local conditions, whereas at the expanding range edge, the invader is likely to encounter challenges that are both novel and unpredictable. We thus expected invasion-vanguard populations to exhibit less phenotypic plasticity than range-core populations. Compared to clutches from long-colonized areas, clutches from the invasion front were indeed less plastic (i.e. rates of larval growth and development were less sensitive to density). In contrast, those rates were highly variable in clutches from the invasion front, even among siblings from the same clutch under standard conditions. Clutches with highly variable rates of growth and development under constant conditions had lower phenotypic plasticity, suggesting a trade-off between these two strategies. Although these results reveal a strong pattern, further investigation is needed to determine whether these different developmental strategies are adaptive (i.e. adaptive phenotypic plasticity vs. bet-hedging) or instead are driven by geographic variation in genetic quality or parental effects.表型可塑性（phenotypic plasticity）可提升物种在新颖且胁迫性环境中的存续能力，因此当生物遭遇新颖环境时，其反应规范（reaction norms）理应发生演化。生物入侵为这类演化变化的研究提供了严谨可靠的实验体系。我们以澳大利亚入侵性蔗蟾（Rhinella marina）的蝌蚪为研究对象，在不同幼体密度条件下，对多个采样地点种群的早期生长与发育速率进行了测定。长期定居区域的种群已拥有充足时间适应当地环境，而处于扩张范围边缘的入侵种群则可能面临兼具新颖性与不可预测性的生存挑战。因此我们推测，入侵先锋种群（invasion-vanguard populations）的表型可塑性应低于分布核心区种群（range-core populations）。实验结果表明，与长期定居区域的卵群相比，入侵前沿的卵群确实表现出更低的表型可塑性，即幼体生长与发育速率对种群密度的敏感性更低。与之相对，入侵前沿卵群的生长与发育速率存在极高的变异度，即使是同一卵群的同胞个体在标准环境下亦是如此。在恒定环境中生长发育速率变异度较高的卵群，其表型可塑性更低，这表明这两种策略之间存在进化权衡。尽管本研究揭示了清晰的演化模式，但仍需进一步探究以明确：这些不同的发育策略究竟是适应性的（即适应性表型可塑性与避险策略（bet-hedging）之间的权衡），还是仅由遗传质量（genetic quality）的地理差异或亲本效应（parental effects）所驱动。