Institute of Vertebrate Biology, Czech Academy of Sciences, Brno, Czech Republic.
Department of Botany and Zoology, Faculty of Science, Masaryk University, Brno, Czech Republic.
Mol Ecol. 2023 Nov;32(22):6070-6082. doi: 10.1111/mec.17173. Epub 2023 Oct 20.
Host-parasite dynamics involve coevolutionary arms races, which may lead to host specialization and ensuing diversification. Our general understanding of the evolution of host specialization in brood parasites is compromised by a restricted focus on bird and insect lineages. The cuckoo catfish (Synodontis multipunctatus) is an obligate parasite of parental care of mouthbrooding cichlids in Lake Tanganyika. Given the ecological and taxonomic diversity of mouthbrooding cichlids in the lake, we hypothesized the existence of sympatric host-specific lineages in the cuckoo catfish. In a sample of 779 broods from 20 cichlid species, we found four species parasitized by cuckoo catfish (with prevalence of parasitism of 2%-18%). All parasitized cichlids were from the tribe Tropheini, maternal mouthbrooders that spawn over a substrate (rather than in open water). Phylogenetic analysis based on genomic (ddRAD sequencing) and mitochondrial (Dloop) data from cuckoo catfish embryos showed an absence of host-specific lineages. This was corroborated by analyses of genetic structure and co-ancestry matrix. Within host species, parasitism was not associated with any individual characteristic we recorded (parent size, water depth), but was costly as parasitized parents carried smaller clutches of their own offspring. We conclude that the cuckoo catfish is an intermediate generalist and discuss costs, benefits and constraints of host specialization in this species and brood parasites in general.
寄生虫与宿主的动态关系涉及协同进化的军备竞赛，这可能导致宿主特化和随之而来的多样化。我们对寄生性鸟类和昆虫类群中宿主特化进化的普遍理解受到限制，因为我们只关注了这些类群。慈鲷口孵鱼（Synodontis multipunctatus）是坦噶尼喀湖慈鲷父母照顾的专性寄生鱼。考虑到该湖口孵慈鲷的生态和分类多样性，我们假设慈鲷口孵鱼中存在同域的宿主特异性谱系。在对 20 种慈鲷物种的 779 窝鱼卵样本中，我们发现有 4 种慈鲷被慈鲷口孵鱼寄生（寄生率为 2%-18%）。所有被寄生的慈鲷都属于口孵鱼慈鲷部落，它们在基质上产卵（而不是在开阔水域中）。基于慈鲷口孵鱼胚胎的基因组（ddRAD 测序）和线粒体（Dloop）数据的系统发育分析显示，不存在宿主特异性谱系。这一结论得到了遗传结构和共同祖先矩阵分析的证实。在宿主物种内，寄生与我们记录的任何个体特征（亲鱼大小、水深）都没有关系，但寄生的亲鱼携带的自身后代的卵更少，这对它们来说是有代价的。我们的结论是，慈鲷口孵鱼是一种中间泛化种，并讨论了该物种和一般的寄生性鱼类中宿主特化的成本、收益和限制。
