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.

当物种快速分化以占据一系列生态位时，便会发生适应辐射（adaptive radiation）。由于不同生态位中寄生虫感染与传播的机会差异极大，适应辐射预计会伴随寄生虫群落的周转更替。作为自然选择与性选择的主要介导因子，寄生虫可能在宿主多样化过程中发挥核心作用。因此，对寄生虫群落周转的研究具有普遍学术意义，且可显著加深我们对适应辐射的理解。本研究针对坦噶尼喀湖慈鲷鱼类的多个适应辐射类群之一——饰颊丽鱼族（Tropheini）的11个物种的寄生虫区系展开了调查。饰颊丽鱼族中最符合简约性原则的祖先觅食策略为相对非选择性的周丛生物（aufwuchs）基底刮食。多个演化支演化出了更为特化的觅食策略，例如选择性梳取显微级硅藻，或是拾取大型无脊椎动物。研究发现，这些特化演化支的类群，其经食物网传播的棘头虫类蠕虫（acanthocephalan helminths）感染率显著降低，但直接生活史寄生虫的感染率并无此类变化。推测选择性觅食策略的演化，导致宿主摄入棘头虫无脊椎中间宿主的概率下降。本研究最终认为，饰颊丽鱼族中的部分物种，其营养特化的附带效应，实际上使其几乎完全免于棘头虫感染。