/ Evidence for a Species-Level Distinction of Two Co-occurring Asters: Aster Puniceus L. And Aster Firmus Nees
ï~~1999 THE MICHIGAN BOTANIST 21 METHODS For this investigation we collected specimens and directly examined living plants from several sites across southern Michigan and analyzed herbarium specimens at the University of Michigan Herbarium (MICH). A total of 22 Aster puniceus and 40 A. firmus plants were collected from co-occurring populations at seven sites across southern Michigan: Waterloo State Recreation Area (Washtenaw County), Pinckney State Recreation Area (Washtenaw County), Hadley Road (Washtenaw County), Furstenburg Park (Ann Arbor City Park, Washtenaw County), Ives Road Fen (Nature Conservancy Preserve, Lenawee County), Lost Nation State Game Area (Hillsdale County), and Bakertown Fen (Nature Conservancy Preserve, Berrien County). Plants were collected from September to November in 1993, 1994 and 1995. Specimens were pressed, dried, and later examined. Five voucher specimens were deposited at MICH (Warners A. firmus 747, 757, 758; A. puniceus 756, 745, MICH). All remaining specimens are retained at the Calvin College Herbarium in Grand Rapids, Michigan. From the collected specimens we quantified rhizome length, leaf midvein pubescence and capitulescence structure, and used these data to graphically illustrate differences. Specimens were collected with as much below-ground material as possible so that various rhizome lengths could be assessed (see Figure 1). Midvein pubescence was measured by averaging hair counts per millimeter of midvein from three leaves per plant under a dissecting microscope. These measurements were taken from the abaxial surface of cauline leaves at an arbitrary location within 3 cm from the base of the leaf. To quantify differences in capitulescence architecture we created a variable, mean BRC (Branching Ratio in the Capitulescence). Mean BRC is the mean ratio of non-flowering to flowering segments (cm) on the three lowermost capitulescence branches (Figure 2). We also gathered data from living plants in coexisting populations at Warren Townsend Park (Kent County), Pickerel Lake Nature Preserve (Kent County), Flat River State Game Area (Montcalm County), Waterloo State Recreation Area (Washtenaw County), Ives Road Fen (Lenawee County), and Bakertown Fen (Berrien County). Observations were made between 3 July and 30 August 1998. At these sites we collected data for three variables (stem thickness, number of shoots per plant and stem pubescence) from a total of 22 Aster puniceus and 28 A. firmus plants. Stem thickness was measured at a point 20 cm above the soil surface. The number of living shoots (current year) from the base of a plant was counted after sufficient surface soil was removed to confidently assess which shoots emerged from the same below-ground structure. Stem pubescence was measured by counting the number of hairs (per 25 mm2) on the stem at a point 60 cm above the soil surface. To assess data from a broader geographical region than southern Michigan, 148 specimens of Aster puniceus and 68 specimens of A. firmus were examined at MICH by qualitatively evaluating four characters: pubescence in the capitulescence, stem pubescence, pubescence on abaxial surface of leaf midveins, and underground parts. A complete list of citations for each of these specimens may be requested from the authors.
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