Global island biogeography of the largest plant family: Asteraceae

The hyperdiverse family Asteraceae, containing an estimated 25,000-33,000 species, forms an iconic component of island floras worldwide. A global picture of Asteraceae diversity on islands is needed to understand the family’s success, but past research has focused on specific archipelagos or single insular lineages. Here, we compile a curated global checklist of Asteraceae native and endemic to islands and combine it with island and environmental data to explore global biogeographic and taxonomic patterns as well as drivers of diversity. We find that there are approximately 5,500 Asteraceae species native to islands, nearly 2,000 of which are endemic. Despite these impressive numbers, Asteraceae is not the most diverse plant family on islands overall and has a lower proportion of insular species than other large Angiosperm families. However, Asteraceae is the most diverse plant family on oceanic islands for natives and second for endemic species, suggesting an exceptional ability to diversify particularly in environments with high ecological opportunity. The main insular hotspots for overall Asteraceae diversity are Madagascar, the Greater Antilles, and the Canary Islands, and species richness of the 31 Asteraceae tribes is unevenly distributed globally. In agreement with island biogeography theory, we find that native diversity increases with area and decreases with isolation, and endemic diversity increases with both area and isolation. With its global perspective, our analysis brings us closer to understanding the reasons for the remarkable macroevolutionary success of this plant family.

Psiadia dentata Renunion Island