Microgeographic adaptation to temperature in pitch pine progenies

Localized variation in cold tolerance of pitch pine (Pinus rigida Mill.) seedlings from an area including a large frost pocket was examined over an autumn, winter and spring. Sizable differences in cold tolerance were discovered among population and individual-tree progeny samples, as measured by patterns of acclimation and maximum levels of cold tolerance achieved. Differences in cold tolerance were associated with local differences in temperature between populations separated by 8 km (over most of which the species occurs only sporadically), but not within a continuous population over a distance of 3.4 km.