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Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Flores Rentería, Lluvia Hilda [1], Molina Freaner, Francisco [2], Marquez-Guzman, Judith [3], Whipple, Amy V. [4], Gehring, Catherine [5], Dominguez, Cesar [6].

Sexual expression in Pinus johannis: implications for the evolution of reproductive systems in seed plants.

The evolutionary process to sexual separation has been poorly studied in gymnosperms even when their reproductive systems are characterized by unisexual structures in either monoecious (individuals bearing male and female structures) or dioecious (populations with unisexual individuals, male and female) systems. Therefore bisexuality has been considered as an innovation of angiosperms regardless of the anecdotal reports of “teratological” bisporangiate structures in gymnosperms. Here we simultaneously study the viability of bisporangiate structures and sexual separation of a gymnosperm and their implications to our knowledge on seed plants reproduction. Pinus johannis represents an opportunity to study these aspects because it is a diverged pine that has unisexual and monoecious individuals, which are also able to produce bisporangiate (bisexual) cones. We characterize the reproductive system and evaluated the stability of the sexual expression in P. johannis by performing survey assays and field experiments. Manual crosses were performed to evaluate if inbreeding depression could be a force to promote sexual separation. Viability of unisexual and bisporangiate cones in Pinus johannis was determine using anatomical and histological methods. We found that P. johannis has a paradioecious reproductive system and the sexual expression is stable. Bisporangiate cones of P. johannis produce functional pollen and ovules. Male and female organs occupy basal and apical positions, respectively, the same positions found in almost all bisporangiate strobili in gymnosperms and bisexual flowers in angiosperms. High inbreeding depression was found in the selfing crosses (autogamy and geitonogamy) and could be a force that promoted sexual separation. The viability and spatial distribution of female and male organs of bisporangiate cones and their frequent occurrence in gymnosperms suggest a common mechanism in all seed plants for the production of bisporangiate structures. The lack of bisporangiate structure in gymnosperms may be primarily due to selection to avoid inbreeding rather than to genetic constraint. This study shows that the sexual systems of gymnosperms are more complex than was previously thought.

Broader Impacts:

1 - Northern Arizona University, Biological Science, South Beaver Street, Bldg 21, Room 227, Flagstaff, AZ, 86011-5694, USA
2 - INSTITUTO DE ECOLOGIA UNAM, APARTADO POSTAL 1354, HERMOSILLO, SONORA, N/A, 83000, Mexico
3 - UNIVER NAC AUTONOMADE MEXICO, CIUDAD UNIV AP 70-356, MEXICO, DF, 04510, México
4 - NNorthern Arizona University, South Beaver Street, Bldg 21, Room 227, Flagstaff, AZ, 86011-5694, United States
5 - Northern Arizona University, Department of Biological Sciences, BOX 5640, Flagstaff, AZ, 86011, USA
6 - Instituto De Ecologia, UNAM, Circuito Exterior S/n, Ciudad Universitaria, UNAM, A.P. 70-275, Mexico DF, N/A, 04510, Mexico

Keywords:
dioecy
monoecy
unisexuality
bisporangiate cones
gymnosperms
Pinus johannis.

Presentation Type: Oral Paper:Papers for Topics
Session: 47
Location: Jasperwood/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 2:30 PM
Number: 47005
Abstract ID:495
Candidate for Awards:Katherine Esau Award,Maynard F. Moseley Award