Floral color variation and associations with fitness‐related traits inMalva moschata(Malvaceae)

Abstract

Genetic polymorphisms for floral color are interesting phenomena to study because they are likely to be maintained by opposing selective forces. Pollinator preferences may exert direct selection on floral color; however, floral color might also be the indirect target of selection through genetic associations with other traits under selection. Malva moschata (Malvaceae) is a North American species that produces either red or white flowers. In the present study, we present reflectance spectrophotometry data that characterize the nature of floral color variation in this species and show that honey bees and bumble bees should be able to distinguish between the morphs through differential sensitivity at the green (long-wavelength) photoreceptor. Second, we use a series of phenotypic measures to investigate whether the color morphs differ with respect to other floral traits, vegetative traits or female reproductive success, and use a series of correlation analyses to infer the relative independence of color from these other traits. We found that red-flowered morphs produced more anthers per flower and had greater leaf area, and that whiteflowered morphs had greater percentage fruit set; however, there were no reproductive success differences between the morphs. The relationship between flower size and anther number was the only correlation that differed between the morphs. Finally, a series of pollinator-choice experiments showed that bumble bees strongly prefer red morphs in terms of visit frequency and duration, but honey bees have no preference. Taken together, our results suggest that color is rather independent of other phenotypic traits, and that honey bee abundance is likely to play a role in maintaining color variation in this system.

Unpredictability of nectar nicotine promotes outcrossing by hummingbirds in Nicotiana attenuata

“…Nectar nicotine levels were not correlated with any other measured floral trait such as nectar volume, nectar sugar concentration or emission of benzylacetone, the main floral attractant. These results are consistent with other studies that have found that floral traits evolve independently of each other in response to different floral visitors (Mazer and Hultgard, 1993; Frey et al. , 2011).…”

Flower colour and visitation rates of Costus arabicus support the ‘bee avoidance’ hypothesis for red‐reflecting hummingbird‐pollinated flowers

“…However, such interspecific comparisons are less useful when used to infer the processes underlying pollinator shifts by two reasons: (i) the a priori choice of exclusively bee-or hummingbird-pollinated species and (ii) the impossibility to isolate a single target trait from other interspecific/intraspecific floral variations. In this sense, a discrete intraspecific variation allows the discrimination of a specific trait function, simultaneously controlling for other trait variations (Medel, Botto-Mahan & Kalin-Arroyo 2003;Frey, Dunton & Garland 2011). Moreover, there is evidence supporting pollinator indifference or preference for intraspecific variation of floral traits (Waser & Price 1981;Goulson & Wright 1998;Medel, Botto-Mahan & Kalin-Arroyo 2003).…”

Current conservation status and reproductive biology of the giant tree Rhododendron in China

“…The measurement covers 250 to 750 nm using 0.38-nm increments. We only measured reflectance pattern per petal since there should be no difference within the same petal but there may be some differences among plants (Frey et al 2011). In total, we took one measure per petal, per flower from a total of 38 flowers sampled from 10 randomly selected individuals (2-4 flowers per individual).…”

“…Additionally, the red flower color of R. protistum var. giganteum might not only provide a strong signal for bird pollination, but also attract bumblebees as exemplified in Malva moschata whose red flower individuals get more visitation of bumblebees than white flower plants (Frey et al 2011) and R. cynocarpum whose flower visitors are mostly bumblebees, accounting for 90% of total visits (Ma et al 2014).…”