Such pleiotropic effects will interact with the pollinator community to either maintain or enforce floral color polymorphism. Anthocyanins, a primary floral pigment, are related to tolerance against abiotic stresses such as UV-B radiation, heat, and drought, as well as non-pollinator biotic pressures such as herbivore defense. Differences in seed set, seed weight, and seed predation under different environmental conditions have been documented between color morphs. Selection by non-pollinator agents can also lead to floral color polymorphism. In Mimulus aurantiacus, where red and yellow ecotypes inhabit different habitats, hummingbirds and hawkmoths show strong preference for red and yellow morphs, respectively, hence both pollinator preferences and ecogeographic isolation has led to assortative mating, thereby maintaining the flower color polymorphism between populations. For Ipomoea purpurea, pollinator constancy by bumble bees resulted in assortative mating within a population, while in Clarkia xantiana, floral color polymorphism is maintained via a combination of positive frequency-dependent pollinator preference by one bee species and negative frequency-dependent pollinator preferences by two other bee species. Pollinator preference and constancy may result in assortative mating, limiting gene flow between the morphs within a population. Numerous studies have demonstrated that pollinators are often the primary selective agent maintaining floral color polymorphisms both within and between populations. Floral color polymorphisms vary both within and between populations and a variety of selective agents have been implicated in their maintenance. Among these traits, floral color polymorphisms are the most visually striking and thus have drawn many researchers to investigate the cause and maintenance of intraspecific variation. Floral traits reported to vary intraspecifically include corolla length and corolla flare, calyx length, flower size and style length, and floral color. Polymorphisms for floral traits occur in many angiosperm species, and the underlying evolutionary forces maintaining these polymorphisms have long been the subject of interest and debate among evolutionary biologists. While many previous studies have provided evidence for pollinator preference playing a role in floral color polymorphism, the results of the current study indicate that reproductive assurance, which would be important for fluctuations in pollinator abundance or colonizing new areas, may act as a selective agent to maintain such polymorphisms.
The apparent trade-offs between a higher reproductive output in the scarlet morph and a reproductive assurance advantage in the yellow morph may explain the maintenance of the polymorphism in C.
When pollinators were excluded, the yellow morph outperformed the scarlet morph in fruit set and seed set. When the scarlet morph was the maternal plant it had higher seed set. Both color morphs were used as pollen donors for the within and between crosses. The hand-pollination treatments were either self-pollination or cross pollination using pollen from within and between populations. coccinea by conducting hand-pollination experiments in two nearby populations, one predominantly yellow and one predominantly scarlet. We investigated a possible mechanism for this maintenance of bract color polymorphism in C. Populations of scarlet Indian paintbrush ( Castilleja coccinea) in the Midwestern United States exhibit a bract color polymorphism, with each population having predominantly yellow or scarlet bracts.
0 kommentar(er)
