Evolution and maintenance of pollen-colour dimorphisms in Nigella degenii: habitat-correlated variation and morph-by-environment interactions
Dimorphism in pollen colour is rare among flowering plants, but occurs in two geographically and morphologically distinct subspecies of Nigella degenii (Ranunculaceae). We evaluated the role of genotype-by-environment interactions in the maintenance of two pollen morphs within each of these subspecies. Morph frequencies in a number of populations were related to current habitat conditions, and an