A One-Two Punch

Abstract

Ecology Climate change is expected to shift the ranges of many species as they attempt to follow the thermal envelope to which they are presumably adapted. As the planet warms, this may produce novel communities and interactions between species. This is because species do not exist in isolation but as parts of large communities of interacting species. Milazzo et al. now report one such example by studying two closely related species of wrasse (rainbow and ornate) in the Mediterranean Sea. Rather than shift their ranges, they found that the cool-water species of fish shifted to a less-preferred seagrass habitat and reduced its level of activity when the density of the warmer-water species within the same enclosure was high. Interestingly, these shifts were not seen at cooler water temperatures and were only observed at high water temperatures when the ratio of the warm-water to cool-water species was high. Thus, in this particular example, the cooler-water species make these changes only when faced with the dual injury of both warmer water and interspecific competition. Furthermore, as species individually begin to respond to their changing environments, unexpected interactions and impacts among species are likely to occur. As the climate changes, we should begin to expect the unexpected. J. Anim. Ecol. 10.1111/j.1365-2656.2012.02034.x (2012).