Rethinking angiosperm diversification through the functional integration of mutualisms

Akira Yamawo 

Flowering plants have maintained exceptional diversity for over 100 million years despite repeated environmental change and mass extinction events. A central challenge in plant macroevolution is understanding how lineages achieve both extensive diversification and long-term persistence. While pollination, seed dispersal, and mycorrhizal symbioses are recognized as key drivers of plant evolution, they are typically studied in isolation, limiting our understanding of how their combined effects influence diversification dynamics. Here, I propose that angiosperm diversification may be better understood through a framework that considers the functional integration of multiple mutualisms operating across the plant life cycle. Within this framework, pollination is expected to contribute disproportionately to lineage divergence through reproductive isolation, whereas seed dispersal and mycorrhizal symbioses may contribute more strongly to lineage persistence by enhancing establishment success, spatial expansion, environmental buffering, and recovery from disturbance. Importantly, these mutualisms are unlikely to act independently; instead, their interactions may generate functional complementarity across life-history stages, potentially coupling processes of diversification and persistence. I term this organizational hypothesis a Functionally Integrated Symbiotic System (FISS), a conceptual framework for understanding how multiple mutualisms may collectively influence lineage divergence and persistence across evolutionary timescales. By shifting attention from pairwise interactions to the higher-order organization of symbiotic systems, FISS generates testable predictions regarding how alternative mutualistic configurations may influence diversification and persistence in angiosperms. More broadly, this framework suggests that large-scale evolutionary dynamics may emerge from the hierarchical integration of ecological interactions into coordinated functional systems, and provides an organizational perspective for interpreting how multiple mutualisms may jointly shape macroevolutionary patterns.