Host evolutionary history drives  prokaryotic diversity in the globally distributed sponge family Petrosiidae (Order Haplosclerida)
Marine sponges maintain a long-standing symbiotic relationship with a vast diversity of microbial organisms, which contribute significantly to marine ecosystem functioning and serve as a rich source of bioactive compounds. While host identity is recognized as a major determinant of microbiome diversity, the underlying evolutionary mechanisms remain poorly understood. In this study, we comprehensively assessed phylosymbiosis patterns within the sponge family Petrosiidae across a broad geographic scale encompassing 23 species. Using 28S rRNA, 18S rRNA, and COI gene barcoding to identify host sponges, combined with 16S rRNA gene amplicon sequencing to characterize prokaryotic communities, we provide strong evidence of phylosymbiosis through multiple analytical approaches, including distance-based metrics, topological congruence, and phylosignal analyses. Our results show that host phylogeny and taxonomy play a significant role in structuring sponge microbiomes, even at finer taxonomic resolutions. Additionally, we also identify environmental and geographical differences in sponge microbiome composition. We hypothesize that while greater phylogenetic distances increase phylosymbiosis signals, closely related host-taxa are more strongly influenced by environmental and biogeographical factors. The exact mechanisms that lead to why phylosymbiosis occurs remain largely unknown. Vertical transmission, ecological filtering, and host-specific traits are likely contributors, but further research on certain aspects related to phylosymbiosis such as integrating geographic, environmental, and taxonomic components are essential. This study represents the first large-scale investigation of phylosymbiosis in sponges at the family level, providing valuable insights into the evolutionary and ecological drivers shaping sponge microbiomes.