Heterogeneous selection on trichome production in Alaskan Arabidopsis kamchatica (Brassicaceae)

? Premise of the study: Environmental heterogeneity is thought to be one of the primary factors in the evolutionary maintenance of morphological variation. Here, we explore the role of environmental heterogeneity in the maintenance of variation in leaf hair (trichome) production in Arabidopsis kamchatica. ? Methods: We investigate abiotic correlates of trichome production in A. kamchatica via surveys of both herbarium specimens and wild populations. In addition, we examine patterns of phenotypic selection on trichome production among populations that differ in environmental characteristics. ? Key results: Trichome-producing herbarium specimens were more likely to occur at lower latitudes and in locations with lower mean annual precipitation and less annual variation in temperature than glabrous specimens. In surveys of wild populations, frequencies of trichome-producing plants were higher in drier habitats than in wetter environments. Using phenotypic selection analysis, we found divergent selection through female fitness (fruit production) on trichome number in populations that differ in environmental characteristics; there was selection for reduced trichome number in one population and selection for increased trichome number in another population. In a population containing both glabrous and trichome-producing plants, glabrous plants produced significantly more fruits than trichome-producing individuals, which indicates selection against the trichome morph. ? Conclusions: Our results demonstrate that there is heterogeneity in selection among populations, which could be responsible for the maintenance of trichome variation in Alaskan populations of A. kamchatica.