Ornamentals lead the way: global influences on plant invasions in the Caribbean

Abstract

Understanding the historical factors associated with the invasion success of alien species in a region may help us to identify sources, vectors, and pathways that are more likely to originate new invaders. Here, we gather data for traits related to the history of introduction (e.g., continent of origin, reason for introduction, and date of introduction) of 616 alien plant species listed as invasive on 18 island groups across the Caribbean region. We used these data to evaluate how human activity has influenced plant invasions on Caribbean islands over time and whether invasion success could be driven by traits of the introduction process. We found that significantly more invasive plants (54%) were intentionally introduced for ornamental reasons than for any other purpose. Most invaders in the Caribbean are native to Asia, South America, and Africa and the cumulative number of invasive species in this region has been steadily increasing during the last 200 years, but since 1850, this trend has been led by species introduced as ornamentals. We also found a significant association between continent of origin and reason of introduction, with more invaders than expected being ornamentals from Asia and America, and forage species from Africa. Our results show that introduced ornamentals are successfully invading all major habitats across the Caribbean, exacerbating conservation issues and threatening native biodiversity. Armed with knowledge of origins and reasons for introductions, effective biosecurity actions as well as control and management strategies can be better targeted to address the problem of invasive species in the region.