PARENT SESSION
Oral Session #5: Plant Demography and Reproductive Ecology.
Presiding: R. Kobe
Monday, August 5. 8:00 AM to 11:30 AM. Coconino Meeting Room, TCC.
Experimental analysis of biparental inbreeding in a self-fertilizing plant, Aquilegia canadensis.
Muis, Celine*,1, Eckert, Christopher2, 1 Department of Botany, Toronto, Ontario, Canada2 Department of Biology, Kingston, Ontario, Canada
ABSTRACT- Restricted dispersal and localized mating may genetically structure plant populations, resulting in matings among related individuals. This biparental inbreeding has significant evolutionary consequences, especially for the evolution of mating systems, yet it is difficult to estimate directly in natural populations. We used two allozyme marker genes to estimate biparental inbreeding in four populations of the largely self-fertilizing plant Aquilegia canadensis using standard inferential methods as well as a novel experimental approach in two populations, which involved moving plants to random locations within populations. Combined self-fertilization and biparental inbreeding (E) estimated with the "effective selfing model" accounted for most matings in all populations (mean E ± SE = 0.621 ± 0.031). In addition, covariation (D) between E and parental gene fixation was significant in three of four populations (Mean D = 0.104 ± 0.014). This implies significant genetic substructure within populations, and that plants in inbred neighbourhoods effectively selfed more than those in outbred neighbourhoods. Estimates of the proportion of progeny produced via biparental inbreeding (r) inferred from the difference between single-locus and multi-locus estimates of selfing (r = ss − sm) indicated that few matings involved close relatives (mean r = 0.0173 ± 0.004). In contrast, randomly relocating plants within populations greatly reduced their level of apparent selfing (mean ss = 0.697 ± 0.057) compared to control plants that had been dug up and replanted in their original locations (0.890 ± 0.088, P = 0.023). Based on the difference in ss between treatments, almost 20% of all outcross matings involved relatives (mean r = 0.193 ± 0.103). Estimates inferred from ss − sm underestimated r in these populations by more than an order of magnitude. Biparental inbreeding is thought to influence the evolution of self-fertilization primarily through reducing the genetic cost of outcrossing. This is unlikely to be of much significance in these populations of A. canadensis because inbreeding depression (a major cost of selfing) is much stronger than the cost of outcrossing.
KEY WORDS: Aquilegia canadensis, inbreeding, mating systems, population structure