Inbreeding Depression and Maternal Effects in Aquilegia Caerulea, a Partially Selfing Plant

Abstract

Little is known about how inbreeding depression and maternal effects change from the seed stage through offspring maturation or how these patterns differ for plants germinated under natural vs. artificial conditions. I measured these effects in perennial Aquilegia caerulea (Ranunculaceae) for both field—sown plants and greenhouse—sown progeny that were subsequently transplanted to the field. Overall, field—sown plants and transplants showed similar cumulative inbreeding depression, averaging 0.54 and 0.52, respectively. Selfed individuals had a lower success than outcrossed individuals in all fitness components measured from the number of seeds produced by the cross of size at year 3, and most effects were significant. Inbreeding depression in survival was worse for field—sown progeny in which mortality was much higher. Furthermore, effects of inbreeding on plant size increased each year for greenhouse—sown transplants, but not for field—sown plants, suggesting inbreeding depression is expressed later when survival is artificially high. The effect of seed mass was investigated in greenhouse—sown individuals. Although selfed seeds weighed significantly less than outcrossed seeds, seed mass was not correlated with emergence or survival. It did, however, correlate with leaf expansion rate, which, in turn, correlated with year 3 size in both transplants and field—sown plants. Maternal effects explained a much larger proportion of variance in seed mass than did level of inbreeding. In the greenhouse, effects of seed parent were strongest on early characters, becoming small and nonsignificant by year 3 when inbreeding effects again become significant. In contrast, maternal effects on juvenile traits of field—sown progeny were negligible.