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The role of inbreeding depression in maintaining the mixed mating system of the common morning glory, Ipomoea purpurea

Publication ,  Journal Article
Chang, SM; Rausher, MD
Published in: Evolution
1999

Theoretical studies show that, although inbreeding depression (ID) will counterbalance the transmission advantage of selfing, it can only maintain a mixed mating system in plants when at least one of the following two conditions is met: (1) there is a positive association between selfing rates and the level of ID; and (2) ID is greater than 0.5 for the female component of fitness, while the average ID for male and female fitness is less than 0.5. This study tests whether these two conditions hold in the common morning glory, Ipomoea purpurea, which has a mixed mating system with 30% self-fertilization. Inbreeding depression was found in all but one fitness component measured in two groups of plants with distinct anther-stigma distances (ASD), a character that influences selfing rates. However, when examined separately, a negative association was found between selfing rates and ID; plants with large ASD (low-selfing-rate genotypes) tended to have higher ID than ones with small ASD (high-selfing-rate genotypes). Furthermore, the overall lifetime ID for male (12.5%) and female (24%) components of fitness, averaged across two ASD groups, were lower than what is necessary for ID to maintain an evolutionarily stable mixed mating system. Therefore, although inbreeding depression contributes to balancing the transmission advantage of selfing, it is not likely to be the primary mechanism maintaining the mixed mating system of I. purpurea. The contribution of other mechanisms is discussed.

Duke Scholars

Published In

Evolution

Publication Date

1999

Volume

53

Issue

5

Start / End Page

1366 / 1376

Related Subject Headings

  • Evolutionary Biology
  • 3104 Evolutionary biology
  • 3103 Ecology
  • 0603 Evolutionary Biology
  • 0602 Ecology
 

Published In

Evolution

Publication Date

1999

Volume

53

Issue

5

Start / End Page

1366 / 1376

Related Subject Headings

  • Evolutionary Biology
  • 3104 Evolutionary biology
  • 3103 Ecology
  • 0603 Evolutionary Biology
  • 0602 Ecology