Cold tolerance of tree species is related to the climate of their native ranges

Abstract

AbstractAimSpecies ranges are confined by environmental parameters such as minimum temperatures. Beyond correlations of ranges and climatic parameters, however, physiological tolerances (here: cold tolerance) have rarely been linked to the climate of species' ranges. We hypothesize that natural range shifts due to climate warming and proactive‐assisted colonization may each be constrained by limits to the tolerance of species to rare frost events.LocationBayreuth, Germany, and the Northern Hemisphere.MethodsWe quantified cold tolerance (LT50 obtained by relative electrolyte leakage method) of 27 native and exotic (Northern Hemisphere) tree species in the autumn, mid‐winter and spring of 2011–12 at the Ecological Botanical Garden of the University of Bayreuth, Germany, and linked observed cold tolerances as well as changes in cold tolerance between sampling dates to the climate of the native ranges of the species.ResultsObserved cold tolerance was strongly related to the climate of the native ranges of the species (cross‐validated correlations between climate and expressed cold tolerance determined by boosted regression trees were 0.50 in autumn, 0.49 in mid‐winter, and 0.65 in spring). Cold tolerance was generally greater for species that experienced colder temperatures and lower levels of precipitation in their native ranges. Changes in cold tolerance between the three sampling dates over the winter, however, were not linked to the climate of the native ranges.Main conclusionsOur results demonstrate the evolutionary importance of cold tolerance, which should be acknowledged in assisted colonization trials and projections of range shifts by considering absolute minimum temperature as an important ecological factor.