Loss of mutualistic interactions loosens restrictions on evolutionary history in legume plant communities

Mutualistic interactions are increasingly recognized as playing important roles in community assembly. We hypothesized that mutualisms can influence the accumulation of evolutionary history within communities through indirect interactions, which we investigated by quantifying the impact of mutualism gains and losses on phylogenetic structure in the Fabaceae family. Analyzing global distribution data, we find that legumes lacking mutualistic interactions exhibit reduced phylogenetic clustering, resulting in higher phylogenetic diversity in regions richer in non-mutualistic legumes. Moreover, the probability of a plant species being introduced to a new range is negatively related to phylogenetic distance to its nearest native relative, but this effect is weaker for species without mutualistic interactions. These findings highlight the significant role of mutualism in restricting the local distribution of evolutionary history at a global scale. Our study advances community assembly theory and underscores the importance of considering mutualism in the conservation and restoration of phylogenetic diversity.