Data from: Parasite escape through trophic specialization in a species flock

Adaptive radiation occurs when species diversify rapidly to occupy an array of ecological niches. Since opportunities for parasite infection and transmission may greatly vary among these niches, adaptive radiation is expected to be associated with a turnover of the parasite community. As major agents of natural and sexual selection, parasites may play a central role in host diversification. The study of parasite turnover may thus be of general relevance and could significantly improve our understanding of adaptive radiation. In the present study, we examined the parasite faunas of eleven species belonging to the tribe Tropheini, one of several adaptive radiations of cichlid fishes in Lake Tanganyika. The most parsimonious ancestral foraging strategy among the Tropheini is relatively unselective substrate browsing of aufwuchs. Several lineages evolved more specialized foraging strategies, such as selective combing of microscopic diatoms or picking of macro-invertebrates. We found that representatives of these specialized lineages bear reduced infection with food-web transmitted acanthocephalan helminths, but not with parasites with a direct life cycle. Possibly, the evolution of selective foraging strategies entailed reduced ingestion of intermediate invertebrate hosts of acanthocephalans. We conclude that some species belonging to the Tropheini virtually escape acanthocephalan infection as a by-product effect of trophic specialization.

适应辐射（Adaptive radiation）指物种快速分化以占据一系列生态位的演化过程。由于不同生态位间寄生虫感染与传播的机会差异悬殊，适应辐射理应与寄生虫群落的更替存在紧密关联。作为自然选择与性选择的核心介导因子，寄生虫可能在宿主分化进程中发挥关键作用。因此，对寄生虫群落更替的研究具备普遍学术意义，或可大幅深化我们对适应辐射机制的理解。
本研究针对坦噶尼喀湖慈鲷鱼类多个适应辐射类群之一的饰首鱼族（Tropheini）的11个物种，开展了寄生虫区系调查。饰首鱼族中最简约的祖先觅食策略为相对非选择性地啃食底栖附着生物（aufwuchs）；多个演化支系随后演化出更为特化的觅食模式，例如选择性梳取微观硅藻，或是捕食大型无脊椎动物。
研究结果显示，这些特化演化支系的类群，经食物网传播的棘头虫类蠕虫（acanthocephalan helminths）感染率显著降低，但直接生活史型寄生虫的感染率并未出现类似变化。推测选择性觅食策略的演化，会伴随棘头虫无脊椎中间宿主的摄入概率大幅减少。
综上，饰首鱼族中的部分物种可通过营养特化的附带效应，几乎完全规避棘头虫感染。