Baskauf, C.J., D.E. McCauley, W.G. Eickmeier, Evolution
(1994) 48: 180-188
Genetic analysis of a rare and a widespread species of Echinacea
(Asteraceae)
Echinacea tennesseensis is an endangered
species known from only a few populations near Nashville, Tennessee. The
population genetics of this highly localized endemic is compared with that
of its widespread prairie relative E. angustifolia var. angustifolia
using allozyme electrophoresis data at 18 loci. The endemic has lower levels
of genetic variability with fewer polymorphic loci (23% vs. 40%), fewer
alleles per locus (1.3 vs. 1.9), and lower levels of heterozygosity (0.069
vs. 0.152). Most variability occurs within rather than among populations,
for both species. Morphological similarities between E. tennesseensis
and E. angustifolia have resulted in a lack of consensus regarding
their taxonomic distinctiveness, but the two are genetically distinct.
Inter-population divergence within each species occurs at significantly
higher genetic identity values (mean identity of 0.991 and 0.984 for E.
tennesseensis and E. angustifolia, respectively) than does divergence
between the species (mean identity of 0.826). In addition, E. tennesseensis
diverges from morphologically distinctive E. purpurea at a similar
mean genetic identity value of 0.813. Thus, the rare E. tennesseensis
has less genetic variability than the widespread E. angustifolia,
and the two differ genetically at a level similar to that found between
E. tennesseensis and a more morphologically distinctive Echinacea
species.