Does Disturbance Drive Hybridisation? A Case Study in Vascular Plants

ABSTRACT Aim Across the tree of life, interspecific gene flow is coming to be recognised not just as an aberrant, albeit common, phenomenon, but as an evolutionary process that is inextricably linked to speciation itself. Empirical evidence and theory taken from adaptive radiations, island migrations, and speciation suggest that ecological disturbance should play a large role in determining when and where gene flow is more likely. In this paper, we expand the canonical definition of disturbance to encompass any climatic, spatial, or geologic factor that may disrupt established niches or adaptive landscapes, and we develop a generalised disturbance hypothesis: Disturbance drives hybridisation. We evaluate the applicability and testability of the generalised disturbance hypothesis using vascular plants as a case study. Location Global. Time Period Current. Taxa Studied Vascular plants. Methods To assess spatial and ecological patterns of hybridisation in vascular plants, we curated the most comprehensive vascular plant occurrence dataset to date, comprising over 300 million records. We use random forest, generalised linear, generalised dissimilarity, and species distribution modelling to assess spatial, climatic, and phylogenetic‐community factors contributing to variation in hybrid occurrence, hybrid abundance, and hybrid community assemblage at both global and regional scales. Results We find moderate support for a generalised disturbance hypothesis, primarily in temperate regions, indicating that climatic instability has played some role in catalysing hybridisation. Hybrid occurrence was predicted with higher accuracy than hybrid abundance in all cases, and we also find decreased explanatory power in tropical regions for all analyses, indicating a need for greater taxonomic effort and emphasising the potential role of idiosyncratic, local‐scale factors in determining outcomes of hybridisation. Main Conclusions This study lays the groundwork to develop a context‐specific interaction model of hybridisation, in which hybridisation is driven in part by regional‐scale geologic and climatic phenomena, and in part by local, lineage‐specific ecological and demographic conditions.