NICHE DIFFERENTIATION AMONG 8 SEXUAL SPECIES OF ANTENNARIA-GAERTNER (ASTERACEAE, INULEAE) AND A ROSEA, THEIR ALLOPOLYPLOID DERIVATIVE

Antennaria rosea is a hybrid polyploid complex that is widespread throughout western North America. The sexual progenitors of A. rosea include A. aromatica, A. corymbosa, A. marginata, A. media, A. microphylla, A. racemosa, A. rosulata, and A. umbrinella. The primary objective of this study was to investigate and quantify the habitat diversity in A. rosea and its sexual progenitors in order to determine whether the individual taxa are ecologically distinct. Ordination of species and environmental variables from the 101 study sites was carried out using Canonical Community Ordination (CANOCO). Results indicate that each sexual species of Antennaria appears to occupy a distinct niche. Both biotic factors, the community associates, and abiotic factors, the environmental variables, could be used to predict which species will occur in a given habitat and vice-versa. Many A. rosea populations did not occupy distinct niches themselves, but instead occupied niches that are very similar to those of their sexual progenitors. Some A. rosea populations occurred on sites which fell in between the groups of sites of the sexual species and these could be described as hybrid habitats. None of the A. rosea sites cover the range of abiotic conditions in which the sexual taxa occur. Antennaria rosea seems to fulfil the prediction that in established floras polyploidy contributes intermediate 'fill-in' taxa that contribute to a more intensive partitioning of niche space. Polyploidy eventually leads to a saturation of most available niches by the progenitor taxa and their polyploid derivatives. This may be the most adaptively significant role that polyploids perform.