Variation in Marginal Populations of Clarkia

Greenhouse—grown progenies from three Clarkia populations were compared with regard to ten morphological and two developmental traits. The "Caliente" population, an undescribed species from a low elevation grassland habitat, has the shortest development time to the first open flower, the narrowest leaves and bracts, the shortest leaf blades and petioles, the smallest flowers. In the latter, self pollination occurs upon opening. A low—land population of Clarkia unguiculata, from a grassland habitat adjacent to the "Caliente" locality, and a mountain population of C. unguiculata from a woodland habitat at a higher elevation both have broader leaves and bracts, larger flowers which are protandrous and outcrossing, and longer development times to the first open flower than does "Caliente". As compared with the lowland population of C. unguiculata, the mountain population has a shorter time between the opening of a flower and its pollination, shorter leaf blades, longer petioles, and a longer development time to the first open flower. The particular traits of each population are discussed in terms of possible adaptive significance relative to their habitats.