Taming Darwin’s conundrum: On the role of phylogenetic and functional differentiation in plant naturalization on oceanic islands

Biological invasions are a major threat to global biodiversity, particularly on oceanic islands and their unique and fragile biotas. However, the complexity of the processes underlying invasions has prevented the identification of general patterns explaining why some plant species successfully establish and spread beyond their native ranges.

We investigated Darwin’s naturalization conundrum in the most species-rich angiosperm family of the Canary Islands, considering two invasion stages across two spatial scales. Using a high-resolution phylogeny covering the Asteraceae species from the archipelago and functional traits measured from fresh specimens, we calculated phylogenetic and functional distances of invasive and noninvasive introduced species to natives.

Our findings reveal that successful introduced Asteraceae species were phylogenetically distant from native relatives, with invasive species even more distantly related than noninvasive introduced species to their closest native relative. Functionally, noninvasive species were distinct, while invasive species showed unexpected similarity to native species. These patterns were consistent across spatial scales.

This study underscores the importance of a multidimensional approach to understanding plant invasion success. Identifying key patterns driving biological invasions is crucial for developing effective strategies against future ecological disruptions on islands.