Mating system and reproductive fitness traits of eastern white pine ( Pinus strobus ) in large, central versus small, isolated, marginal populations

• Published in: Canadian Journal of Botany
• Main Authors: Rajora, Om P, Mosseler, Alex, Major, John E
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2002
• Subjects: Plant Science; Newfoundland
• Online Access: http://dx.doi.org/10.1139/b02-105; http://www.nrcresearchpress.com/doi/pdf/10.1139/b02-105

Multilocus (t m ) and single-locus (t s ) outcrossing and actual inbreeding rates and seed traits were determined for eastern white pine (Pinus strobus L.) in six small, remnant, and marginal populations from two regions (East and West) in Newfoundland and in three large populations from the center of the species' geographic range in Ontario to examine the effects of small population size and fragmentation on mating system parameters and reproductive fitness. The population t m ranged from 0.867 to 0.991, with a mean of 0.924 over all nine populations. The mean t s ranged from 0.672 to 0.908, with a mean of 0.797 over the nine populations. The Ontario populations, on average, showed higher but statistically similar outcrossing rates (t m = 0.947, t s = 0.848) to the Newfoundland populations (t m = 0.912, t s = 0.772). The Newfoundland West populations, on average, showed the lowest outcrossing rates (t m = 0.889, t s = 0.716). Individual family outcrossing rates, although slightly higher, were similar to their respective population outcrossing rates, and no significant differences were observed among families within populations. The mean t s were significantly lower than their corresponding t m , and the differences were significantly and positively correlated with the number of loci showing significant regression of pollen allele frequency on ovule genotype, suggesting possible occurrence of consanguineous mating. The Ontario populations showed the highest and the Newfoundland West populations the lowest reproductive fitness, with Newfoundland East populations ranking higher than Newfoundland West but significantly lower than Ontario populations. Actual inbreeding rates, determined by combining allozyme-based estimates of selfing in the filled seed component with estimates of inbreeding from the proportions of empty seeds, ranged from 7.4 to 31.6%, with an average of 22% for all populations and 11.1% for the Ontario, 24.7% for the Newfoundland East, and 30.1% for the Newfoundland West populations. Multilocus ...