/ Evidence for a Species-Level Distinction of Two Co-occurring Asters: Aster Puniceus L. And Aster Firmus Nees
ï~~24 THE MICHIGAN BOTANIST Vol. 38 60 0O A. puniceus 0 A. firmus " E 50 40 0 0 4) 4).2 c; 30 u0 K 20 * 01 " " S 10 FIGURE 3. A comparison of belowground structures of the o two asters: length to pre0 0 20 vious year's shoot plotted 0 1,0 " 20 30 40 50 against the mean length Length to previous year's shoot (cm) to next year's shoot. to have variable numbers of cauline leaf midvein hairs (> = 6.8/mm, sd = 2.3), while A. firmus midveins were typically glabrous (> = 0.14/mm, sd = 0.37). The two anomalous individuals (one A. puniceus without hairs and one A. firmus with hairs) maintained other characters consistent with their taxon. Mean BRC was consistently lower in A. puniceus (x = 0.86, sd = 0.39) than in A. firmus (x = 3.38, sd = 1.43), indicating that the heads of A. firmus are much more crowded along the outermost part of the capitulescence. Observations of living plants in the field yielded additional quantitative data that further delineate the two asters. Figure 5 illustrates these differences using the variables stem thickness (at 20 cm above the soil surface), number of shoots from the base of a plant, and number of stem hairs (per 25 mm2 on the stem 60 cm above soil surface). Aster puniceus can grow in clumps of several shoots per plant (> = 2.4, sd = 1.6), whereas we always found A. firmus shoots arising singly (x = 1.0, sd = 0). Aster puniceus also commonly displays thicker stems (x = 7.2 mm, sd = 1.5) than A. firmus (x = 4.0, sd = 0.93) and the stems of A. puniceus are more densely pubescent (x = 15.7, sd = 4.5) than are the stems of A. firmus (x = 2.3, sd = 1.9). The qualitative data gathered from specimens at MICH illustrate general trends in pubescence differences and further supported differences we had quantified from below-ground material. Four comparisons in pubescence patterns were made (Table 1). Stem and leaf pubescence occurred more commonly and at greater density in Aster puniceus. However, pubescence in the capitulescence was found in distinct lines more frequently in A. firmus. We also attempted to compare below-ground material from the MICH specimens (Figure 6). Unfortunately, the majority of herbarium specimens (over 60%) did not include sufficient below-ground material to make such a comparison. However, of those with sufficient root material, the vast majority of Aster puniceus specimens exhibited a caudex, and nearly all A. firmus specimens had extended rhizomes.
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