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THE MICHIGAN BOTANIST
Vol. 38
O A. puniceus
0 A. firmus
0
00
0 0 0 0
0
4
2 16 3 6
0 0 0
2 3
0 0
ol
T
I
3 4 5 6 7 8
Stem Thickness (mm)
9 10
E
U
W
U
E
a)
0
0 0 0
00
0
0
0
FIGURE 5. Evaluation of stem thickness, number of shoots
and stem pubescence from
living plants. (a) Stem
thickness measured at 20
cm above the soil surface
plotted against the number
of shoots arising from the
base of an individual
plant. Points accompanied
by numbers represent the
number of individuals
which shared identical
values. (b) Stem pubescence measured at 60 cm
above the soil surface
plotted against stem thickness measured at 20 cm
above the soil surface.
5 " "
" ".1
n
3 4 5 6 7 8
Stem Thickness (mm)
9 10
and other traits, we found little evidence of introgression, leading us to suggest
these taxa should be classified as two distinct species. The differences we found
are particularly noteworthy since we limited our quantitative comparisons to
plants that were existing in overlapping populations. If the two Asters are of the
same species, cross-fertilization and intermediate forms would be expected, especially in areas where the plants co-occur (Wagner & Wagner 1983). Yet we
found no evidence that supports the existence of intermediate forms, even
though all the plants we evaluated were from coexisting populations.
A comparison of below-ground structures of these Asters produced the most
significant contrast. The stout caudex of Aster puniceus differs markedly from
the extended rhizomes of A. firmus. We found that A. firmus shoots typically produce 2-6 rhizomes beginning in mid to late summer, each eventually reaching
between 20-70 cm in length by late fall. To our knowledge these are the longest
0
