Invaders in waiting? Non-equilibrium in Southern Hemisphere seaweed distributions may lead to underestimation of Antarctic invasion potential

Abstract

Bioinvasions pose a major threat to global biodiversity. Correlative Ecological Niche Models (ENMs) can be a valuable tool to identify invaders and invasion sites. However, in cases when species are in non-equilibrium with their native environment (i.e. do not fill their niche), correlative approaches have limited power and invasions lead to shifts of the realized niche. In recent years, several new seaweed species have been reported in Antarctica. It is impossible to unequivocally identify which of these species are truly non-natives, however, here, we provide literature-based evidence that seaweed species have been introduced to Antarctica. Under this assumption, we reconstruct pre-and post-introduction niches of these species, calculate relative niche sizes and overlap between pre-Antarctic and Antarctic sites, and Highlights• Non-native Antarctic species likely originate from climatically non-matching and distant habitats • Shifts in realized niches might be common during introductions to Antarctica • Southern Hemisphere seaweeds in particular, and perhaps other intertidal organisms, in the Southern Hemisphere exhibit non-equilibrium distributions and might be "invaders in waiting" • Purely correlative approaches to identify potential Antarctic invaders are insufficient