EVIDENCE FOR INTROGRESSION IN AZALEAS (RHODODENDRON, ERICACEAE) - CHLOROPLAST DNA AND MORPHOLOGICAL VARIATION IN A HYBRID SWARM ON STONE MOUNTAIN, GEORGIA

Hybridization and introgression have been suggested by previous worker s as important factors in the evolution of the southeastern azaleas. H owever, because of high levels of intraspecific variation and lack of intensive sampling, documentation of this phenomenon has been difficul t. We investigated a population of azaleas on Stone Mountain, Georgia, composed of Rhododendron flammeum, R. canescens, and their interspeci fic hybrids. After analysis of chloroplast DNA, we found evidence of e xtensive localized cytoplasmic introgression into R. flammeum. Many in dividuals in the sample population that are morphologically indistingu ishable from R. flammeum possess the chloroplast genome of R. canescen s. This suggests that some of the observed variation in some populatio ns of R. flammeum may be due to past introgression from R. canescens.