title: Context-dependent reproductive isolation mediated by floral scent and color.
abstract: Reproductive isolation due to pollinator behavior is considered a key mode of speciation in flowering plants. Although floral scent is thought to mediate pollinator behavior, little is known about its effects on pollinator attraction and floral visitation in the wild. We used field experiments with wild hawkmoths and laboratory experiments with naïve hawkmoths to investigate attraction to and probing of flowers in response to indole, a volatile emitted by Ipomopsis tenuituba but not its close relative I. aggregata, both alone and in combination with floral color differences. We demonstrated that indole attracts wild hawkmoths to flowers, but has little effect on the rate at which those attracted moths probe flowers. In contrast, white flower color did not influence hawkmoth attraction in the field, but caused more attracted moths to probe flowers. Thus, the moths require both scent and high visual contrast, in that order, to feed at flowers at dusk. Their preference for indole-scented flowers is innate, but species-specific preference is mitigated by previous experience and plant spatial patterning. This context-dependent behavior helps explain why these Ipomopsis species show geographical variation in the extent of hybridization and may potentially explain formation of hybrid bridges in other systems of hawkmoth-pollinated plants.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Irvine, California, 92697; Rocky Mountain Biological Laboratory, Crested Butte, Colorado, 81224; Department of Neurobiology and Behavior, Cornell University, Ithaca, New York, 14853.
authors.forename: Mascha
authors.initials: M
authors.lastname: Bischoff
authors.forename: Robert A
authors.initials: RA
authors.lastname: Raguso
authors.forename: Andreas
authors.initials: A
authors.lastname: Jürgens
authors.forename: Diane R
authors.initials: DR
authors.lastname: Campbell
mesh_terms: D000818:Animals; D035264:Flowers / Q000235:genetics* / Q000378:metabolism; D049810:Genetic Speciation; D007211:Indoles / Q000378:metabolism / Q000494:pharmacology; D019684:Magnoliopsida / Q000235:genetics* / Q000502:physiology; D009036:Moths / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D009812:Odorants; D010858:Pigmentation; D054817:Pollination; D060047:Reproductive Isolation; D012903:Smell; D014785:Vision, Ocular
chemical_list: D007211:Indoles
keywords: Floral volatiles; Ipomopsis; hawkmoth; pollinator preference; reproductive isolation; speciation