Temporal aspects of the assembly of arbuscular mycorrhizal (AM) fungal communities within plant roots have been posited as critical drivers of the plant-fungal symbiotic outcomes. However, the functional implications of these dynamics remain poorly understood. We conducted a controlled pot experiment with Sorghum bicolor to investigate how temporal shifts in AM fungal community composition and phylogenetic diversity influence plant growth and phosphorus responses to the symbiosis. We characterised the root-colonising AM fungal communities across three time points. Joint species distribution modelling with Hierarchical Modelling of Species Communities (HMSC) framework revealed a strong phylogenetic signal, indicating that temporal changes in AM fungal communities were closely linked to their phylogenetic relatedness. The temporal phylogenetic clustering of AM fungal communities coincided with marked increases in plant biomass and phosphorus responses to the AM fungal symbiosis, suggesting that host filtering of specific fungi was a key determinant of these benefits. Our findings provide compelling evidence that the temporal phylogenetic structuring of AM fungal communities, driven by host-mediated environmental filtering, is important in shaping the functional benefits conferred by the symbiosis. This study advances our understanding of the ecological mechanisms underpinning AM fungal community assembly and their implications for plant performance.