Abstract Detail

Conservation Biology

BYERS , DIANE L [1], Meagher, Thomas R [2].

Dynamics of gynodioecious breeding system in small populations: Genetic drift and the loss of asymmetry in inbreeding.

Populations in highly fragmented environments are subject to genetic drift, which in turn affects breeding systems, including sex ratio dynamics. We have been studying the gynodioecious species Lobelia spicata, which is native to the prairies of Midwestern United States. Our focus has been on the hill and tallgrass prairies in Illinois and Indiana, habitats that are highly fragmented due to intensive agriculture and urbanization/ suburbanization. As variation in the female frequency will influence reproductive success and viability of the populations, we have focused our efforts on understanding the causes and consequences of this variation. Our previous theoretical work proposed that the sex ratio of L. spicata would be more influenced by genetic drift than frequency dependent selection due to this fragmentation. Our previous empirical work in remnant prairies found substantial variation in female frequency (0.096-0.7), with lower pollinator visitation to the nonrewarding female plants and lower seeds/fruit by females when there is a higher frequency of females. While our recent research found soil characteristics may be influencing the frequency of females, genetic drift is also key to understanding variation in breeding system. Here we will present an assessment of the effects of population size, resource reallocation, inbreeding and inbreeding depression on the maintenance of females. The genetic control of the breeding system in L. spicata is most likely cyto-nuclear so we have included this in the genetic design in our model.  With simulations run over 500 generations, we found that under genetic drift females are unlikely to be maintained in populations of less than 150 individuals. If there is very high female seed set advantage (e.g., due to reallocation of resources from male function) females may persist in a population of 150, and even in some cases populations of as few as 50 individuals. However, this level of female advantage (k=0.8) is likely biologically unrealistic. With moderate selfing rates in hermaphrodites and strong inbreeding depression (d=0.9) females may be maintained in populations of 150. We also included biparental inbreeding, allowing seed set by females to experience inbreeding, and found that this had little effect on female frequency in the absence of asymmetry in biparental inbreeding between females and hermaphrodites. This lack of asymmetry has profound implications for the evolution of gynodioecy in small populations.

1 - IL State Univ, School Of Biological Sciences, Campus Box 4120, Normal, IL, 61790, USA
2 - St Andrews University, Biological Sciences, Harold Mitchell Building, St Andrews, Fife, KY169TH, UK

Keywords:
Breeding System
genetic drift
gynodioecy
habitat fragmentation
sex ratio.

Presentation Type: Oral Paper:Papers for Topics
Session: 27
Location: Firs North/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 1:30 PM
Number: 27001
Abstract ID:610
Candidate for Awards:None