Ducatez S, Crossland M, Shine R
School of Biological Sciences, University of Sydney, Sydney, NSW, Australia.
J Evol Biol. 2016 Feb;29(2):335-43. doi: 10.1111/jeb.12785. Epub 2015 Nov 29.
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.
表型可塑性可以增强物种在新的压力环境中生存的能力，因此随着生物体遇到新环境，反应规范预计会发生进化。生物入侵提供了一个强有力的系统来研究此类变化。我们测量了澳大利亚入侵性蔗蟾蜍（海蟾蜍，Rhinella marina）蝌蚪在一系列地点和不同幼虫密度下的早期生长和发育速率。长期定居地区的种群有机会适应当地条件，而在不断扩张的范围边缘，入侵者可能会遇到既新颖又不可预测的挑战。因此，我们预计入侵先锋种群的表型可塑性低于范围核心种群。与长期定居地区的卵块相比，来自入侵前沿的卵块确实可塑性较低（即幼虫生长和发育速率对密度的敏感度较低）。相比之下，来自入侵前沿的卵块中的这些速率变化很大，即使在标准条件下来自同一卵块的同胞之间也是如此。在恒定条件下生长和发育速率变化很大的卵块具有较低的表型可塑性，这表明这两种策略之间存在权衡。尽管这些结果揭示了一种强烈的模式，但仍需要进一步研究以确定这些不同的发育策略是适应性的（即适应性表型可塑性与风险对冲），还是相反，是由遗传质量或亲本效应的地理变异驱动的。
