Origins of the Macaronesian flora: Dispersal and diversification shape a meta‐archipelago

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PREMISE: Ancestors of oceanic insular floras arrived via long-distance dispersal as a function of the geographic location, climatic habitats, and geologic age of the island. As a result, these floras comprise a mix of lineages, derived from distinct colonization events with different continental and insular origins. METHODS: We assembled distributional data for native plant species in four Macaronesian archipelagoes (Azores, Madeira, Canary Islands, and Cabo Verde). Drawing from phylogenetic studies, we assigned each endemic species to a lineage. Five regions represent where the closest relatives of these lineages occur: American, temperate northern Europe, Mediterranean, Saharan, and African. We then estimated the total number of colonization events to Macaronesia as a whole and each constituent archipelago deriving from each region. RESULTS: The distribution of the origins of native non-endemic lineages broadly reflects the range of climates available in a given archipelago, such that a habitat filter model best explains their distributions. In contrast, for endemic lineages, combinations involving the Mediterranean region predominate across all four archipelagoes. The most species-rich lineages most commonly originate in the Canaries and subsequently disperse to younger, more isolated archipelagoes, reflecting a progression rule pattern. CONCLUSIONS: Different theoretical models apply depending on the scale of endemism. One pattern that transcended existing models involved instances where an archipelago that promotes ecological diversification serves as a stepping stone for the colonization of more distant archipelagoes that otherwise may not have been suitable for ancestral continental taxa, which we term the island springboard effect.

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