Host Evolutionary History Drives Prokaryotic Diversity in the Globally Distributed Sponge Family Petrosiidae.

Sponge microbial communities play a crucial role in marine ecosystem functioning and serve as a rich source of bioactive compounds. While host identity is recognised as a major determinant of microbiome diversity, the underlying evolutionary mechanisms remain poorly understood. This study aimed to comprehensively assess phylosymbiosis patterns within the sponge family Petrosiidae. In total 21 sponge species, collected across a broad geographic scale, were examined to investigate how host phylogeny influences microbiome composition. Using 28S rRNA, 18S rRNA and COI gene barcoding to identify host sponges, combined with 16S rRNA gene amplicon sequencing to characterise prokaryotic communities, we provide evidence of phylosymbiosis through multiple analytical approaches, including distance-based metrics and topological congruence. Our results show that host phylogeny and identity play a significant role in structuring sponge microbiomes, even at finer taxonomic resolutions. However, we observed notable incongruencies, where closely related sponge species exhibit divergent microbial communities that appear to be associated with depth or geographical location. 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, particularly in the sponge family Petrosiidae.