Data from: The evolution of life cycle complexity in aphids: ecological optimization, or historical constraint?

For decades, biologists have debated why many parasites have obligate multi-host life cycles. Here, we use comparative phylogenetic analyses of aphids to evaluate the roles of ecological optimization and historical constraint in the evolution of life cycle complexity. If life cycle complexity is adaptive, it should be evolutionarily labile, i.e., change in response to selection. We provide evidence that this is true in some aphids (aphidines), but not others (non-aphidines) – groups that differ in the intensity of their relationships with primary hosts. Next, we test specific mechanisms by which life cycle complexity could be adaptive or a constraint. We find that among aphidines there is a strong association between complex life cycles and polyphagy but only a weak correlation between life cycle complexity and reproductive mode. In contrast, among non-aphidines the relationship between life cycle complexity and host breadth is weak but the association between complex life cycles and sexual reproduction is strong. Thus, although the adaptiveness of life cycle complexity appears to be lineage specific, across aphids, life cycle evolution appears to be tightly linked with the evolution of other important natural history traits.数十年来，生物学家始终围绕“为何多数寄生虫拥有专性多宿主生活周期（obligate multi-host life cycles）”这一议题展开争论。本研究以蚜虫为研究对象，通过比较系统发育分析（comparative phylogenetic analyses），评估生态优化（ecological optimization）与历史约束（historical constraint）在生活周期复杂性演化过程中的作用。若生活周期复杂性具备适应性，则其应具有进化易变性，即能够响应自然选择而发生演化改变。研究证实，这一情况在部分蚜虫类群（蚜亚科（Aphidinae））中成立，但在另一类群（非蚜亚科（non-aphidines））中却并非如此——这两类群与初级宿主的关联强度存在差异。随后，研究人员针对生活周期复杂性可具备适应性或受约束的具体机制开展检验。结果发现，在蚜亚科类群中，复杂生活周期与多食性（polyphagy）之间存在显著关联，但生活周期复杂性与繁殖方式（reproductive mode）之间的相关性却较弱。与之相反，在非蚜亚科类群中，生活周期复杂性与宿主范围（host breadth）之间的关联较弱，但复杂生活周期与有性生殖（sexual reproduction）之间却存在显著关联。因此，尽管生活周期复杂性的适应性似乎具有谱系特异性，但在整个蚜虫类群中，生活周期的演化似乎与其他重要自然历史性状（natural history traits）的演化紧密相关。