Abstract Detail

Development and Structure

Grant, Alannie-Grace [1], Callodonato, Rebecca [2], Litt, Amy [3], Kalisz, Susan [1].

Is reduced apical height of conical petal cells a new trait in the selfing syndrome?

Understanding the morphological and functional changes that are associated with significant evolutionary transitions is a fundamental goal in evolutionary biology. One of the most common evolutionary transitions in angiosperms is from outcross-fertilization to self-fertilization. In many species a suite of morphological and functional changes accompanies the shift to selfing, collectively termed the “selfing syndrome.” These include traits that increase the efficacy of self-fertilization, like the reduction of temporal and spatial overlap of reproductive parts and pollen-to-ovule ratios, as well as reductions in pollinator attraction traits: floral scent, nectar, and flower size. Such changes in floral attractive trait investment can result in reduced costs of flower production and potentially increased seed number and reproductive success for selfing species. A novel function of a floral trait, the presence of conical petal cells (CPC), has been identified in Antirrhinum. In a set of behavioral assays, it was determined that bees that visit wild type Antirrhinum flowers (wild type CPC expression) have increased foraging success relative to bees that visit mutant flowers that lack CPC expression (flat epidermal cells). Bees on flowers with CPCs retain a grip on the petals of large, showy, zygomorphic flowers, which facilitates outcross pollination. On petals with only flat epidermal cells, bees are unable to maintain their grip on flowers, which reduces outcross reproductive success. CPCs have been documented in ~80% of angiosperm taxa examined, yet little is known about differences in surface abundance CPCs or morphology between plant species with predominantly outcrossing vs. selfing mating systems. We hypothesize that highly self-fertilizing species will have significant reductions in the relative petal area covered by CPC and apical height of CPC cells compared to outcrossing species. We test this hypothesis by quantifying the percent petal area covered by CPC and the apical height of individual petal cells imaged using scanning electron microscope (SEM). We contrast these metrics in two selfing/outcrossing sister species pairs in the genus Collinsia (Plantaginaceae) [C. rattanii/C. linearis and C. parryi/C. concolor]. Our results show that the selfing species have a reduced percent area of CPCs and nearly exclusively flat petal cells compared to their outcrossing sister species. These results suggest that reduced CPCs may be an additional trait in the selfing syndrome.

1 - University of Tennessee, Knoxville, Department of Ecology and Evolutionary Biology, Knoxville, TN, USA
2 - University of Pittsburgh, Department of Biological Sciences, Pittsburgh, PA, USA
3 - University of California, Riverside, Department of Botany and Plant Sciences, Riverside, CA, USA

Keywords:
conical cells
selfing
pollination
selfing syndrome
Collinsia
flower petals
Scanning Electron Microscopy.

Presentation Type: Oral Paper
Session: 49, Developmental and Structure II
Location: 205/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 4:00 PM
Number: 49002
Abstract ID:859
Candidate for Awards:None