Genetic diversity, population structure, and ancestry estimation in the Antennaria rosea (Asteraceae: Gnaphalieae) polyploid agamic complex

Antennaria rosea, a polyploid agamic complex, originated from hybridization, polyploidization, and introgression of as many as eight diploid/tetraploid sexual Antennaria species in the Rocky Mountains of North America. The species shows tremendous variation within and among populations including phyllary coloration, number and arrangement of heads per flowering stalk, and leaf size/shape leading to the enumeration of many microspecies and a taxonomic challenge. A comprehensive evolutionary study of these populations would clarify the origins and evolution of A. rosea as a polyploid agamic complex. Using genetic markers developed for Antennaria species, genetic diversity, population structure, and ancestry estimation of 18 A. rosea populations distributed in the Rocky Mountains of the U.S.A. were studied. Comparatively, A. rosea populations distributed in the Northern Rocky Mountain region had higher levels of genetic diversity than the populations in the southern Rocky Mountain region. Antennaria rosea populations were divided into three genetically distinct clusters, and populations within each genetic cluster showed high correlations regarding geographic distribution and ancestry. Two of the putative parents, A. microphylla and A. umbrinella, were the major sources of parentage for A. rosea populations, and notably, these species were widely distributed and sympatric with most of the A. rosea populations from this study. A novel finding of this study was that each of the A. rosea populations had its origins from different sexual progenitors and, although A. microphylla and A. umbrinella were the major contributors to the parentage of most of the A. rosea clones sampled, the other six sexual species also contributed to a lesser degree to their origins. Our study also indicated that sympatry of parents contributes substantially to the origination of polyploid populations of A. rosea