Minimal loss of genetic diversity and no inbreeding depression in blueflag iris (Iris versicolor) on islands in the Bay of Fundy

Abstract

Isolated island plant populations founded by few individuals are often characterized by decreased genetic variation and increased inbreeding. Our aim was to measure population genetic diversity and inbreeding depression in blueflag iris (Iris versicolor L., Iridaceae), a native allotetraploid, on islands in the Bay of Fundy, Canada. Hand-pollination experiments (inbreeding, within-site outbreeding, between-island outbreeding) on Kent Island, New Brunswick, revealed no evidence for inbreeding depression across a broad array of morphological, physiological, and life-history traits. Leaf tissue samples collected from three mainland sites and 10 islands in the Bay of Fundy and genotyped using three microsatellite primer pairs showed that island populations were less genetically diverse than mainland populations. Island populations were genetically distinct from each other, indicating a bottleneck effect associated with colonization and continued isolation. Nonetheless, substantial genetic variation was maintained at the population level. Polyploidy and a history of self-fertilization may allow Iris versicolor to avoid inbreeding depression in isolated populations. Our study supports Anderson’s (1936) original hypothesis that substantial genetic diversity can be preserved within polyploid species, even with extensive inbreeding.