Strong selection is generated for traits that have large effects on reproductive success. In flowering plants, this has resulted in taxa exhibiting flowers that are able to attract pollinators and optimize both pollen export and receipt. Floral pigment has been well-studied in this ecological context, with much research investigating the roles of this trait in plant-pollinator interactions. However, only a handful of studies have examined ontogenetic variation in petal pigment as individual flowers progress through development, often transitioning between functional “gender” stages. Quantifying this variation and understanding how it influences fitness is critical to fully understanding how plants communicate with their pollinators.
The Californian wildflower Clarkia unguiculata exhibits protandrous sequential hermaphroditism in addition to extensive variation in floral pigment traits, offering an ideal system to test our hypotheses. We performed a greenhouse study with ~300 plants, aiming to quantify ontogenetic variation in petal pigmentation. Two petals each from floral stages representing two “male” and one “female” phase per plant were collected and photographed. Using a modified ImageJ Plugin, we were able to generate multispectral images in the visual range of pollinators (specialized Hymenopterans) in addition to treat individual pigment features as continuous traits, fully encompassing each petals’ complexity.
Results/Conclusions
Preliminary analyses have shown that petals of C. unguiculata change significantly through ontogeny, with increases in area, UV absorbance, and luminance contrast as flowers progress from “male” to “female” function. These traits have been found in previous studies to be positively correlated with higher pollinator attraction. In addition, these results demonstrate the importance of keeping track of ontogeny when studying floral traits.
In the following field season, we will perform pollinator studies to determine the direct ecological roles of ontogenetic variation in floral pigment, by measuring its effects on pollinator behavior and pollen export in natural populations of C. unguiculata. Our findings will aid in understanding the mechanisms through which plants communicate with their pollinators, an increasingly important field of study for conservation and agricultural efforts as pollinators undergo global decline.