ALLOZYME DIVERGENCE AMONG FIVE DIPLOID SPECIES OF ANTENNARIA (ASTERACEAE: INULEAE) AND THEIR ALLOPOLYPLOID DERIVATIVES

The Antennaria parlinii and A. neodioica agamic complexes are widely distributed across North America. Morphological data have suggested that these dioecious, perennial, entire-leaved herbs are of multiple hybrid origin from among five sexual diploid species. Antennaria neglecta, A. plantaginifolia, A. racemosa, and A. virginica are hypothesized to be the diploid progenitors of the A. neodioica complex, whereas A. parlinii sensu lato is thought to include the genomes of A. plantaginifolia, A. racemosa, and A. solitaria. An electrophoretic study was initiated to assess the degree of divergence among the five diploid species and to test the hypotheses of the hybrid (allopolyploid) origins of A. parlinii and A. neodioica. Twenty genetic loci were surveyed in 76 populations of the diploid and polyploid taxa. The diploid species are well defined morphologically, although the genetic basis of differences distinguishing them have not been determined. The species exhibit little divergence at genes specifying soluble enzymes, however each species has unique alleles in highest frequency at one or two genes. Allozymes indicate that gene diversity in the obligately outcrossing diploids occurs primarily within rather than among populations. The shale barren endemic, A. virginica, is as genetically diverse as the more edaphically diverse and widespread species. Tetraploid cytotypes of diploid (2n = 28) A. virginica possess the same allozymes as the diploids and these cytotypes appear to be of autopolyploid (non-hybrid) origin. Enzyme electrophoresis is concordant with morphological data in suggesting that A. neodioica contains the genomes of A. neglecta, A. virginica, A. plantaginifolia, A. racemosa and perhaps A. solitaria whereas the latter three species are the progenitors of A. parlinii.