Environmental warming increases invasion potential of alpine lake communities by imported species

Global warming increasingly pressures species to show adaptive migratory responses. We hypothesized that warming increases invasion of alpine lakes by low-elevation montane zooplankton by suppressing native competitors and predators. This hypothesis was tested by conducting a two-factor experiment, consisting of a warming treatment (13 vs. 20°C) crossed with three invasion levels (alpine only, alpine+montane, montane only), in growth chambers over a 28-day period. Warming significantly reduced total consumer biomass owing to the decline of large alpine species, resulting in greater autotrophic abundance. Significant temperature-invasion interactions occurred as warming suppressed alpine zooplankton, while stimulating certain imported species. Herbivorous invaders suppressed functionally similar alpine species while larger native omnivores reduced invasion by smaller taxa. Warming did not affect total invader biomass because imported species thrived under ambient and warmed alpine conditions. Our findings suggest that the adaptability of remote alpine lake communities to global warming is limited by species dispersal from lower valleys, or possibly nearby warmer alpine ponds.