Data from: Simultaneous evolution of multiple dispersal components and kernel

Global climate is changing rapidly and is accompanied by large-scale fragmentation and destruction of habitats. Since dispersal is the first line of defense for mobile organisms to cope with such adversities in their environment, it is important to understand the causes and consequences of evolution of dispersal. Although dispersal is a complex phenomenon involving multiple dispersal-traits like propensity (tendency to leave the natal patch) and ability (to travel long distances), the relationship between these traits is not always straight-forward, it is not clear whether these traits evolve simultaneously or not, and how their interactions affect the overall dispersal profile. To investigate these issues, we subjected four large (N~2500) outbred populations of Drosophila melanogaster to artificial selection for increased dispersal, in a setup that mimicked increasing habitat fragmentation over 33 generations. The propensity and ability of the selected populations were significantly greater than the non-selected controls and the difference persisted even in the absence of proximate drivers for dispersal. The dispersal kernel evolved to have significantly greater standard deviation and reduced values of skew and kurtosis, which ultimately translated into the evolution of a greater frequency of long-distance dispersers (LDDs). We also found that although sex-biased dispersal exists in Drosophila melanogaster, its expression can vary depending on which dispersal component is being measured and the environmental condition under which dispersal takes place. Interestingly though, there was no difference between the two sexes in terms of dispersal evolution. We discuss possible reasons for why some of our results do not agree with previous laboratory and field studies. The rapid evolution of multiple components of dispersal and the kernel, expressed even in the absence of stress, indicates that dispersal evolution cannot be ignored while investigating eco-evolutionary phenomena like speed of range expansion, disease spread, evolution of invasive species and destabilization of metapopulation dynamics.

全球气候正发生快速变化，同时伴随生境的大规模破碎化与破坏。由于扩散（dispersal）是移动生物应对环境逆境的首要防御策略，因此解析扩散演化的成因与后果具有重要意义。尽管扩散是涉及多种扩散性状的复杂现象，例如扩散倾向（propensity，即离开出生斑块的倾向）与扩散能力（ability，即长距离移动的能力），但这些性状间的关联并非总是直接明确的，目前尚不清楚这些性状是否会同步演化，以及它们的相互作用如何影响整体扩散表型。为探究这些问题，我们对4个大型远交黑腹果蝇（Drosophila melanogaster）种群（每个种群样本量约2500）进行了扩散能力提升的人工选择实验，实验设置模拟了33代持续增加的生境破碎化过程。选择种群的扩散倾向与扩散能力均显著高于未选择的对照组，且即使在缺乏直接扩散诱因的环境中，这种差异依然保持。扩散核（dispersal kernel）演化出了显著更大的标准差，以及降低的偏度与峰度，这最终导致长距离扩散者（long-distance dispersers, LDDs）的频率大幅提升。我们还发现，尽管黑腹果蝇中存在性别偏向的扩散现象，但其表现会因所测量的扩散组分以及扩散发生的环境条件而异。但有趣的是，两性在扩散演化层面并未表现出显著差异。我们讨论了本研究部分结果与以往实验室及野外研究不一致的潜在原因。即使在无胁迫的条件下，扩散多组分与扩散核仍能快速演化，这表明在探究范围扩张速率、疾病传播、入侵物种演化以及集合种群（metapopulation）动态失稳等生态-演化现象时，扩散演化的影响不容忽视。