Animals have been developing key associations with micro-organisms through evolutionary processes and ecological diversification. Hence, in some host clades, phylogenetic distance between hosts is correlated to dissimilarity in microbiomes, a pattern called phylosymbiosis. Teleost fishes, despite being the most diverse and ancient group of vertebrates, have received little attention from the microbiome perspective and our understanding of its determinants is currently limited. In this study, we assessed the gut microbiome of 12 co-occurring species of teleost representing a large breadth of ecological diversity and originating from a single family (i.e., the Sparidae). We tested how host evolutionary history, diet composition and morphological traits are related to fish gut microbiome. Despite fish species having different microbiomes, there is no phylosymbiosis signal in this fish family, but gut length and diet had a strong influence on the microbiome. We revealed that the only species with a specialized herbivorous diet, Sarpa salpa had a 3.3 times longer gut than carnivorous species and such a long gut favor the presence of anaerobic bacteria typical of herbivorous gut microbiomes. Hence, dietary uniqueness is paired with both unique gut anatomy and unique microbiome.

动物已经通过进化过程和生态多样化发展了与微生物的关键关联。因此，在某些寄主进化枝中，寄主之间的系统发生距离与微生物群落的相似性相关，这种模式称为共生共生。硬骨鱼类尽管是脊椎动物中种类最多，最古老的一组，但从微生物组的角度来看却很少受到关注，目前我们对其决定因素的了解还很有限。在这项研究中，我们评估了12个硬骨鱼类共生物种的肠道微生物组，这些物种代表着广泛的生态多样性，并且起源于单个家庭（即Sparidae）。我们测试了宿主进化史，饮食组成和形态特征与鱼肠道微生物组的关系。尽管鱼类具有不同的微生物群，该鱼类家族中没有任何共生信号，但是肠道长度和饮食对微生物组有很大影响。我们揭示了仅有的具有特殊草食饮食的物种，萨尔帕舞肠道比肉食性物种长3.3倍，而如此长的肠道有利于存在草食性肠道微生物群典型的厌氧细菌。因此，饮食的独特性与独特的肠道解剖结构和独特的微生物组结合在一起。