Measuring, comparing and interpreting phenotypic selection on floral scent

• Published in: Journal of evolutionary biology Vol. 35; no. 11; pp. 1432 - 1441
• Main Authors: Opedal, Øystein H., Gross, Karin, Chapurlat, Elodie, Parachnowitsch, Amy, Joffard, Nina, Sletvold, Nina, Ovaskainen, Otso, Friberg, Magne
• Format: Journal Article
• Language: English
• Published: Switzerland Oxford University Press 01.11.2022; Wiley; John Wiley and Sons Inc
• Subjects: Animal communication; Animals; Attraction; Biodiversity; Biologi; Biological Sciences; Botanics; Cactus; cognition; Cognitive ability; data collection; Ecology; Ecology, environment; Ekologi; Evolutionary Biology; Evolutionsbiologi; floral fragrance; floral scent; Flowers - physiology; Life Sciences; Methods; Natural Sciences; Natural selection; Naturvetenskap; Odorants; odors; Phenotype; Phenotypes; phenotypic selection; Pheromones; Physiological responses; plant–pollinator interactions; Pollen; Pollination; Pollinators; reduced-rank regression; selection gradient; Symbiosis; uncertainty; Vegetal Biology; Volatile compounds; Volatile Organic Compounds; Volatiles; selection gradient; floral fragrance; floral scent; plant-pollinator interactions; natural selection; reduced-rank regression
• ISSN: 1010-061X; 1420-9101; 1420-9101
• DOI: 10.1111/jeb.14103

Natural selection on floral scent composition is a key element of the hypothesis that pollinators and other floral visitors drive scent evolution. The measure of such selection is complicated by the high‐dimensional nature of floral scent data and uncertainty about the cognitive processes involved in scent‐mediated communication. We use dimension reduction through reduced‐rank regression to jointly estimate a scent composite trait under selection and the strength of selection acting on this trait. To assess and compare variation in selection on scent across species, time and space, we reanalyse 22 datasets on six species from four previous studies. The results agreed qualitatively with previous analyses in terms of identifying populations and scent compounds subject to stronger selection but also allowed us to evaluate and compare the strength of selection on scent across studies. Doing so revealed that selection on floral scent was highly variable, and overall about as common and as strong as selection on other phenotypic traits involved in pollinator attraction or pollen transfer. These results are consistent with an important role of floral scent in pollinator attraction. Our approach should be useful for further studies of plant–animal communication and for studies of selection on other high‐dimensional phenotypes. In particular, our approach will be useful for studies of pollinator‐mediated selection on complex scent blends comprising many volatiles, and when no prior information on the physiological responses of pollinators to scent compounds is available. Graphical summary of the reduced‐rank regression approach to estimating phenotypic selection on floral scent composition. The method reduces complex scent chemistry into a scent composite trait under selection (i.e. that is most strongly associated with variation in fitness), and estimates the strength of selection on this composite trait while also considering other phenotypic traits expected to be under selection.