COMPARATIVE ECOLOGY OF THE NARROW ENDEMIC ECHINACEA-TENNESSEENSIS AND2 GEOGRAPHICALLY WIDESPREAD CONGENERS - RELATIVE COMPETITIVE ABILITY AND GROWTH-CHARACTERISTICS

Using a multiple de Wit replacement series, we tested the hypothesis t hat the middle Tennessee cedar glade endemic, Echinacea tennesseensis, is a poor competitor compared with its geographically widespread clos e relatives, Echinacea angustifolia var. angustifolia and Echinacea pa llida. In the competition experiment, all pairwise combinations of the three Echinacea taxa were grown under greenhouse conditions at severa l densities and proportions for 175 d. Classical and functional growth analyses were performed on the three taxa to quantify physiological a nd morphological characteristics that influence competitive ability. T he hierarchy of competitive ability (based on relative yield and aggre ssivity), plant dry mass, and leaf area was E. pallida > E. tennesseen sis > E. angustifolia. However, neither relative growth rate, net assi milation rate, leaf area ratio, nor specific leaf weight differed sign ificantly among the three species (protected least significant differe nce [PLSD], P > .05). We conclude that lack of competitive ability per se cannot account for the narrow endemism of E. tennesseensis.