Adaptive differentiation in Liquidambar styraciflua L. from eastern United States and northeastern Mexico under uniform environmental conditions

Laboratory-germinated seedlings from the United States and Mexico were compared under various environmental conditions. Provenances of the coastal plain and Piedmont of eastern United States had earlier cessation of stem elongation and earlier production of dormant buds Cloud forest provenances from Mexico were less sensitive to daylength and temperature and showed almost continuous growth under an array of environmental conditions. With the exception of a Florida population, Mexico provenances exhibited earlier bud burst in outdoor testing. Populations compared under central Texas conditions for 5 yr continued to show phenological differences among the various provenances The U.S. plants, except those from Florida, were leafless earlier than the Mexico plants each year Seed lots from the United States and Mexico that were compared under Mexico City conditions showed similar patterns to those of central Texas. The Mexico trees had earliest bud burst and latest formation of dormant buds The adaptive variation of the diverse populations of Liquidambar styraciflua L accounts for the broad latitudinal distribution in deciduous forests of eastern United States and in montane cloud forests of Mexico