The integrative ecology of the saddleback anemonefish, Amphiprion polymnus , reveals it is a host generalist across multiple ecological axes

Understanding how symbiosis generates biodiversity requires comprehensive insight into the underlying ecology to reveal broad evolutionary patterns, and the clownfish-anemone symbiosis serves as an excellent model. Recently, a new paradigm revealed sea anemone host associations of adult clownfish drove convergent evolution of host specialists and generalists. An alternative study downplayed host specificity in explaining clownfish evolution due partly to an incongruence between the behavior, biology, and host specificity of a single species— Amphiprion polymnus . Previously classified as a host specialist, we revisit the host specificity and ecology of A. polymnus by studying its host associations, behavioral, and dietary ecology compared to a co-occurring host generalist and specialist. By incorporating n = 358 observations, we find A. polymnus associates with five sea anemone species, including a newly documented host, and four at the adult life stage. We show that A. polymnus swim consistently far from their hosts and have broad dietary niches, an ecology that aligns with generalists. Cumulatively, our data indicate A. polymnus is a host generalist, and not a specialist as previously classified. Our findings serve to reconcile previously conflicting studies about A. polymnus , and reinforce the hypothesis that host is the key ecological variable for understanding clownfish evolution.