Species-specific clonality in east Asian island flora: Phylogenetic and environmental constraints

Plant clonality is a ubiquitous trait observed in many phylogenetic clades and vegetations across tropical to arctic biomes. However, there is no consensus regarding determinant factors of species clonality; especially in the context of species assembly processes, ecological/evolutionary drivers of clonal growth remain largely unknown. To elucidate macroecological drivers of clonality, we examined phylogenetic conservatism/convergence of clonal growth in Japanese vascular plants and explored the ecological role of clonality. We created a dataset of clonal plants that were classified into phalanx, guerrilla and detachable clonal forms for 3,179 species, along with data regarding species geographical distributions and phylogenies. Then, we tested the association of phylogenetic and environmental factors with species clonality for three life-form groups (fern, herb and woody species), and identified explanatory factors of clonal growth along large-scale environmental gradients. Species clonality was phylogenetically constrained; specifically, for herb and woody species, phylogenetic signals across all the clonal growth forms, or especially the detachable form in ferns, were significant. Moreover, clonal growth of Japanese vascular plants was largely explained by taxonomic levels, and also partly by temperature, soil fertility, and species diversity in the distribution range, suggesting both processes; taxon-dependent evolution of vascular plant clonality and evolutionary convergence of clonality across multiple clades of vascular plants relative to environmental constraints. Our findings demonstrated that species-specific clonal growth, which acts as a trait related to abiotic/biotic niche, contributes to shaping large-scale plant diversity patterns through species sorting along abiotic gradients.