MORPHOLOGICAL AND MOLECULAR COMPARISONS OF CAMPSIS-GRANDIFLORA AND CAMPSIS-RADICANS (BIGNONIACEAE), AN EASTERN ASIAN AND EASTERN NORTH-AMERICAN VICARIAD SPECIES PAIR

Morphological and molecular comparisons were made for Campsis grandifl ora (THUNB.) K. SCHUMANN (Bignoniaceae) from eastern Asia and C. radic ans (L.) SEEMANN from eastern North America. Chloroplast DNA (cpDNA) v ariation was surveyed with 20 restriction endonucleases. The cpDNA div ergence between the two vicariad species was 2.44%, which is the highe st reported among North Temperate disjunct taxa and one of the highest reported for infrageneric taxa. Detailed morphological comparisons al so suggest a high level of divergence. Cluster analyses based on 22 mo rphological characters and 39 OTUs revealed two distinct groups corres ponding with the two species. The average taxonomic distance between t he two species was 1.806. Analyses of variance (ANOVA) revealed that 1 2 of the 18 quantitative characters differed significantly (alpha less than or equal to 0.01) between C. grandiflora and C. radicans. Diverg ence time based on cpDNA data was estimated as 24.4 million years. The Bering land bridge hypothesis was favored over the North Atlantic lan d bridge hypothesis based on the estimated divergence time and the geo logical history of the North Temperate region. The high levels of morp hological and cpDNA divergence are not consistent with morphological s tasis, which has been proposed as a common mode of evolution for North Temperate disjunct taxa.