Pollen competition among two species of Senecio (Asteraceae) that form a hybrid zone on Mt. Etna, Sicily

M A Chapman, D G Forbes, R J Abbott

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37 Citations (Scopus)

Abstract

Hybridization between interfertile, sympatric or parapatric, plant species can be reduced significantly by conspecific pollen advantage (CPA), whereby conspecific pollen has an advantage over heterospecific pollen in terms of ovule fertilization. We examined CPA in two interfertile species of Senecio, S. aethnensis, and S. chrysanthemifolius (Asteraceae), which form a hybrid zone on Mt. Etna, Sicily. Individuals of both species were pollinated with pollen mixtures containing 0, 25 50, 75, or 100% heterospecific pollen, and offspring were genotyped to determine if they were products of conspecific or heterospecific pollen fertilizing the ovules. The mean proportion of hybrid offspring produced on S. aethnensis plants was not significantly different to that expected based on the proportion of heterospecific pollen applied to the flower head. However, S. chrysanthemifolius mother plants showed moderate CPA, with the proportion of hybrid offspring significantly less than expected. Seed set or seed germination was not reduced, hence the CPA found for S. chrysanthemifolius acts before ovule fertilization. The consequences of asymmetry in CPA on the reproductive isolation of S. aethnensis are briefly discussed, along with other mechanisms that may play a role in the maintenance of the hybrid zone on Mt. Etna.

Original languageEnglish
Pages (from-to)730-735
Number of pages6
JournalAmerican Journal of Botany
Volume92
Publication statusPublished - Apr 2005

Keywords

  • Asteraceae
  • hybrid zone
  • introgression
  • Mt. Etna
  • pollen competitions
  • reproductive isolation
  • Senecio
  • REPRODUCTIVE ISOLATION
  • HELIANTHUS ASTERACEAE
  • LOUISIANA IRISES
  • CHLOROPLAST DNA
  • TUBE GROWTH
  • IPOMOPSIS POLEMONIACEAE
  • HYBRIDIZATION
  • INTROGRESSION
  • SUNFLOWERS
  • SPECIATION

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