Stronger effect of temperature on body growth in cool than in warm populations suggests lack of local adaptation

Abstract

Body size is a key trait that has been declining in many biological assemblages, partly due to within-species changes in individual growth rates and mean body size attributed to climate warming. Yet, robust tests of warming-effects in natural populations are scarce due to a lack of long time series with large temperature contrasts. We compiled length-at-age data for Eurasian perch (Perca fluviatilis) from 10 populations along the Baltic Sea coast between 1953-2015 (23605 individuals). By fitting von Bertalanffy growth curves to individual length-at-age trajectories, we estimated growth-temperature relationships across large ranges of environmental temperature. We identify a non-linear relationship between growth and temperature, but find little evidence for local adaptation in thermal response curves. Cold populations show a positive response whereas warm populations show a negative response to increasing temperatures. Understanding population-specific effects of warming on growth and size is critical for predicting climate impacts to species and ecosystems.