Abstract Detail

A Colloquium Honoring Leslie D. Gottlieb

Raguso, Robert A. [1], Miller, Timothy J. [2], Kay, Kathleen M. [2].

Novel traits or new neighbors? Exploring the causes and consequences of pollinator shifts in Clarkia.

Pollination biologists continue to debate whether floral traits or community interactions are more important in mediating plant-pollinator interaction networks and their evolution. Leslie Gottlieb and his students used the genus Clarkia to explore questions in plant genetics and systematics, with a particular interest in the evolution of novel traits. His student Eran Pichersky pioneered the molecular study of floral scent using Clarkia breweri as a model, in which scent evolved as a novel trait along with larger and paler colored flowers, presumably in conjunction with a shift to moth pollination. Clarkia breweri and its sibling, C. concinna, embody Harlan Lewis’ concept of “catastrophic speciation”, in which a putative progenitor (C. concinna) with a broad distribution begets a more geographically limited derivative (C. breweri) in a marginal habitat, through climate change and subsequent isolation. In this study we explored the relative impacts of novel floral traits and novel community context on the spectrum of animal visitors to flowers of C. breweri and C. concinna and their relative effectiveness as pollinators. We used field experiments in the Coast Range Mountains of California, USA, as well as flight cage behavioral assays with lab-raised hawkmoths (Hyles lineata). We set out arrays of greenhouse-grown C. breweri and C. concinna in their own and each other’s natural habitats. The community composition of floral visitors was similar between Clarkia species at each site but divergent between sites, reflecting observed visitor differences in natural populations. A spectrum of diurnal bees, long tongued flies and butterflies visited both species in both habitats, whereas hummingbirds and hawkmoths only visited flowers within the range of C. breweri. All of these visitors except hawkmoths were more effective pollinators of C. concinna than of C. breweri, based on pollen transfer to stigmas. Conversely, hawkmoths in flight cage experiments also visited both Clarkia species, but transferred pollen more efficiently to C. breweri than to C. concinna. In field and lab settings, differences in pollen transfer clearly resulted from mechanical fit of visitor to flower, due to the larger floral dimensions of C. breweri. Thus, differences in the available pollinator community play an important role in determining the visitors to natural populations of C. concinna and C. breweri. Trait-related differences in recruiting a novel hawkmoth pollinator come at relatively little cost in attractiveness to other pollinators, but exact a large cost in the efficiency of other pollinators.

Broader Impacts:

1 - Cornell University, Neurobiology and Behavior, W355 Mudd Hall, 215 Tower Road, Ithaca, NY, 14853, USA
2 - University of California, Santa Cruz, Ecology and Evolutionary Biology, 1156 High St. , Santa Cruz, CA, 95064, USA

Keywords:
pollination
regional floral differences
Scent
reproductive isolation.

Presentation Type: Symposium or Colloquium Presentation
Session: C1
Location: Grand Ballroom A/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 9:30 AM
Number: C1005
Abstract ID:492
Candidate for Awards:None