Linking climate change and biological invasions: Ocean warming facilitates nonindigenous species invasions

TLDR

The spread of exotic species and climate change are among the most serious global environmental threats, each causing ecological damage, but data are scarce on whether climate change facilitates invasions by favoring introduced over native species. The study compares long‑term weekly recruitment of sessile marine invertebrates with interannual water temperature variation to evaluate how climate change may influence the success and spread of introduced species. The authors use long‑term recruitment records and laboratory experiments to examine how winter and summer temperature extremes affect growth and recruitment of introduced versus native ascidians. The results show that warmer winters trigger earlier and greater recruitment of introduced ascidians while suppressing native recruitment, and laboratory tests confirm that introduced species grow faster only at high temperatures, indicating that climate change’s impact on biotic communities is driven by temperature extremes and may promote nonnative dominance.

Abstract

The spread of exotic species and climate change are among the most serious global environmental threats. Each independently causes considerable ecological damage, yet few data are available to assess whether changing climate might facilitate invasions by favoring introduced over native species. Here, we compare our long-term record of weekly sessile marine invertebrate recruitment with interannual variation in water temperature to assess the likely effect of climate change on the success and spread of introduced species. For the three most abundant introduced species of ascidian (sea squirt), the timing of the initiation of recruitment was strongly negatively correlated with winter water temperature, indicating that invaders arrived earlier in the season in years with warmer winters. Total recruitment of introduced species during the following summer also was positively correlated with winter water temperature. In contrast, the magnitude of native ascidian recruitment was negatively correlated with winter temperature (more recruitment in colder years) and the timing of native recruitment was unaffected. In manipulative laboratory experiments, two introduced compound ascidians grew faster than a native species, but only at temperatures near the maximum observed in summer. These data suggest that the greatest effects of climate change on biotic communities may be due to changing maximum and minimum temperatures rather than annual means. By giving introduced species an earlier start, and increasing the magnitude of their growth and recruitment relative to natives, global warming may facilitate a shift to dominance by nonnative species, accelerating the homogenization of the global biota.