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Article
Variation in Sex Allocation and Floral Morphology in an Expanding Distylous Plant Hybrid Complex
International Journal of Plant Sciences
  • Jennifer Rhode Ward, University of North Carolina at Asheville
  • M. Leigh Cowart, University of North Carolina at Asheville
  • Julie Clifford, University of North Carolina at Asheville
  • Mieko Camp, Tennessee Technological University
  • Mitchell B. Cruzan, Portland State University
Document Type
Article
Publication Date
4-24-2014
Subjects
  • Morphology (Plants),
  • Hybridization,
  • Sex allocation,
  • Turneraceae
Disciplines
Abstract

Premise of research. Sex allocation, the relative energy devoted to producing pollen, ovules, and floral displays, can significantly affect reproductive output and population dynamics. In this study, we investigated floral morphology and gamete production in bisexual, distylous plants from a self-incompatible hybrid complex (Piriqueta cistoides ssp. caroliniana Walter [Arbo]; Turneraceae). Sampling focused on two parent types (C, V) and their stable hybrid derivative (H). Since H morphotypes are heterotic for growth and fruit production, we hypothesized that they would produce larger flowers with more gametes. We also anticipated that plants with long styles (long morphs) would produce less pollen than short morphs, since long-morph pollen is larger.

Methodology. Over two consecutive summers, flowers were collected from 1465 individual plants in 28 field populations. Floral parameters were measured digitally, and each flower’s pollen number, ovule number, and stigma-anther separation was quantified under a dissecting microscope. Gamete production (n = 332) and stigma-anther separation (n = 119) were also quantified for plants from a greenhouse accession.

Pivotal results. Floral display differed among morphotypes, with H plants producing the largest flowers and C plants displaying the least petal separation. Hybrid morphotypes produced significantly more pollen than parental morphotypes, and pollen quantity was significantly greater for long morphs. Ovule production, however, was greatest for V flowers. Stigma-anther separation differed between years and style morphs (greater for short morphs) but not among morphotypes or within a single season.

Conclusions. Differences in pollen production between morphs were not consistent with trade-offs in pollen size and number or selection for increased male function in short morphs. Greater stigma-anther separation in short morphs supported the hypothesis of selection to reduce pollen interference. Enhanced floral display and pollen production followed other heterotic traits observed in H morphotypes. The superior ability of H morphotypes to attract pollinators and sire seeds might partially explain this hybrid zone’s continuing expansion.

Description

Copyright 2014 by The University of Chicago.

This is the publisher's final PDF, reproduced with permission.

DOI
10.1086/675695
Persistent Identifier
http://archives.pdx.edu/ds/psu/11929
Citation Information
Ward, J. R., Cowart, M. L., Clifford, J., Camp, M., & Cruzan, M. B. (2014). Variation in Sex Allocation and Floral Morphology in an Expanding Distylous Plant Hybrid Complex. International Journal of Plant Sciences, 175(5), 518-525.