Abstract Detail

On models and methods pertaining to plant reproduction

CARUSO , CHRISTINA MARIE [1], Case , Andrea L.  [2].

Confronting models with data: the case of sex-ratio evolution in gynodioecious plants.

Although most plant species are hermaphroditic, separate sexes have evolved repeatedly in the angiosperms. The evolution of separate sexes has puzzled biologists since Darwin because unisexual plants are at an inherent disadvantage relative to hermaphrodite plants. Consequently, there has been extensive research by both mathematical modelers and field biologists into the conditions that allow unisexual plants to persist. But are field biologists testing the key predictions of models of the evolution of separate sexes, and do these models meaningfully capture the biology of gender-dimorphic plant species?
To answer these questions, we will focus on models of the evolution of gynodioecy, a breeding system in which individuals are either female or hermaphroditic. Models predict that the cost of restoration, a negative pleiotropic effect of nuclear sex- determining genes on hermaphrodite fitness, is the key determinant of the persistence and frequency of females in gynodioecious populations. Specifically, females are predicted to be more common in populations where there is a high cost of restoration. Despite this prediction, the cost of restoration has rarely been measured by field biologists.
We describe a method that field biologists can use to estimate the cost of restoration in natural populations of gynodioecious species. When we used this method in 26 populations of gynodioecious Lobelia siphilitica, we found that the cost of restoration was higher in populations with more females, as predicted by gynodioecy models. However, these models did not provide any insight as to why the magnitude of cost varies so strikingly among L. siphilitica populations. To determine why cost varies, we transplanted L. siphilitica females between populations and used their open-pollinated offspring to measure the cost of restoration. We found that variation in cost among L. siphilitica populations may reflect the distribution of cytoplasmic, rather than nuclear, sex-determining genes. Our results illustrate the value of mathematical models of the evolution of separate sexes, but also their limitations.

1 - University Of Guelph, Department Of Integrative Biology, New Science Complex, 50 Stone Road East, GUELPH, ON, N1G 2W1, Canada
2 - Kent State University, Box 5190, 256 Cunningham Hall, Kent, OH, 44242-0001, USA

Keywords:
gynodioecy
sex ratio
Lobelia
Breeding System.

Presentation Type: Symposium or Colloquium Presentation
Session: SY09
Location: Summit/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 11:15 AM
Number: SY09008
Abstract ID:670
Candidate for Awards:None