Photochemical efficiency is an important component of ecophysiological variation of Cistus albidus between habitats in south-east Spain.

The ecophysiology of Cistus albidus L. plants in a variety of habitats in south-east Spain was measured in situ over the course of a year, to determine whether physiological variation occurs between populations growing in sites exposed to differing temperature and precipitation. Not all the observed variation could be explained by differing contemporary meteorological conditions. In particular, plants at the driest site maintained much higher photochemical efficiency through the summer and autumn than plants at the other sites, and also showed higher stomatal conductance after the autumn rains. Principal component analysis identified photochemical efficiency as the greatest source of variation between populations. Such variation may represent the result of differing selection in populations that have been exposed to different prevailing conditions of mean temperature, precipitation or atmospheric humidity, for long periods of time.