Concordance and discordance: a tale of two hybrid zones in the Pacific Coast irises (Iridaceae)
1996
Young, N.D.
Chloroplast DNA (cpDNA) markers were developed that provided markers unique to a species or that delimited a large area within a species. These markers were then followed across two hybrid zones: Iris douglasiana/Iris innominata, and Iris chrysophylla/Iris tenax. In each case the cline in haplotype frequency was compared to the cline for a morphologically based hybrid index. In all three transects across the I. douglasiana/I. innominata hybrid zone, the cpDNA cline was displaced 1-2 km relative to the morphologically defined hybrid zone: the displacement was not found in the other hybrid zone. The observed displacement represents introgression of cpDNA from I. douglasiana into I. innominata. It may be that the I. douglasiana/I. innominata hybrid zone has shifted in recent time, leaving the slowly dispersing chloroplast DNA behind. The populations known as Iris thompsonii do not form a phylogenetic species and are best viewed as products of hybridization between I. douglasiana and I. innominata.
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