Inbreeding depression in Campanula rapunculoides L. I. A comparison of inbreeding depression in plants derived from strong and weak self-incompatibility phenotypes

Abstract

The evolution of selfing taxa from outcrossing ancestors has occurred repeatedly and is the subject of many theoretical models, yet few empirical studies have examined the immediate consequences of inbreeding in a population with variable expression of self‐incompatibility. Because self‐incompatibility breaks down with floral age in Campanula rapunculoides, we were able to mate outbred and selfed maternal plants in a crossing design which produced progeny with inbreeding coefficients of 0, 0.25, 0.50 and 0.75. Cumulative inbreeding depression in plants that were selfed for one generation was very high in families derived from strongly self‐incompatible plants (average δ = 0.98), and somewhat lower in families derived from plants with weaker expression of self‐incompatibility (average δ = 0.90). Relative to outbred progeny, inbred progeny produced fewer seeds, had lower rates of germination, less vegetative growth and fewer flowers per plant. Inbred progeny also took longer to germinate, and longer to produce a first leaf and to flower. Interestingly, inbred plants also produced 40% fewer seeds than outcrossed plants (t‐test P < 0.001) even when mated to the same, unrelated pollen donor, suggesting that inbreeding can produce profound maternal effects. Most importantly, our results demonstrate that progeny derived from plants with stronger expression of self‐incompatibility exhibited greater levels of inbreeding depression than progeny from plants with weaker expression of self‐incompatibility. Moreover, the decline in fitness (cumulative, ln‐transformed) over the four inbreeding levels was steeper for the progeny of the strongly self‐incompatible lineages. These empirical results suggest that inbreeding depression and mating system phenotype have the potential to coevolve.

Anther-Stigma Separation Is Associated With Inbreeding Depression in Datura Stramonium, a Predominantly Self-Fertilizing Annual

“…Vogler et al (1999) found that individuals of Campanula ranunculoides with weak self-incompatibility reactions showed lower loss of fitness upon selfing than did individuals with strong selfincompatibility reactions. There may have been purging of highly deleterious alleles in the lines with the leaky selfincompatibility.…”

Epistasis in Monkeyflowers

“…The phenotype of an individual may depend not only on its own inbreeding coefficient, but also on that of its mother (Vogler et al 1999). The maternal inbreeding effect can be estimated by comparing plants from reciprocal crosses in which the parents differ in their respective inbreeding coefficients.…”

Effect of variation in herkogamy on outcrossing within a population of Gilia achilleifolia

“…A previous study of Gilia achilleifolia appears to demonstrate that such associations exist; highly herkogamous individuals showed more severe inbreeding depression than individuals with low anther-stigma separation (Takebayashi and Delph, 2000). Several other studies have also found similar correlations between family-level inbreeding depression and traits that influence outcrossing rate (Vogler et al, 1999;Stone and Motten, 2002). However, a multilocus simulation study suggested that genetic associations are unlikely to be observed (Schultz and Willis, 1995).…”