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100 THE MICHIGAN BOTANIST Vol. 55 NOTEWORTHY COLLECTIONS FIRST REPORT OF HYPERICUM ADPRESSUM (HYPERICACEAE) IN MICHIGAN Michael R. Penskar and Beverly S. Walters University of Michigan Herbarium 3600 Varsity Drive Ann Arbor, MI 48108-2228 firstname.lastname@example.org email@example.com Significance of the Report. The first documented report of this native, glob- ally rare, Atlantic Coastal Plain disjunct species from the State of Michigan. Previous Knowledge. Hypericum adpressum Barton (Hypericaceae), Creep- ing St. John�s-wort, is a medium-sized, strongly rhizomatous, perennial wetland forb of seasonally inundated depressional wetlands. Along much of the Atlantic Coastal Plain this species is typically known from various types of intermittent ponds and also from a diversity of other habitats including marshy shores, wet meadows, bogs, swales, ditches, and even moist depressions in sand prairies (Robson 2015; Witsell 2007; Crow and Hellquist 2000; Gleason and Cronquist 1991; Godrey and Wooten 1981). In New England, the habitat is characterized by Enser (2001) as damp sands, gravels, and peats on the exposed shores and inun- dated margins of freshwater ponds, whereas Haines (2011) notes that in this same region it also occurs on river shores and coastal plain pond shores and in sandy and peaty depressions. This native North American species occurs primar- ily from Massachusetts and Rhode Island south to Georgia along the Atlantic Coastal Plain, occurring sporadically to the west with several marked disjunct occurrences documented in Arkansas, Missouri, Illinois, Indiana, Kentucky, and Tennessee (USDA, NRCS 2016). Discussion. We discovered Hypericum adpressum (Figure 1) in the central- west portion of Lower Michigan during natural community and botanical sur- veys in Newaygo County. The nearest record relative to this new Michigan lo- cality (Michigan Flora Online 2011) is from Porter County in northwest Indiana, more than 175 miles away. This follows a pattern strongly similar to the distrib- ution of several other Atlantic Coastal Plain disjuncts known in the upper Mid- west, as described in a thorough overview of this pattern by Reznicek (1994). Al- though Hypericum adpressum may be locally dominant within a site, as amply observed in subsequent visits of our Michigan discovery, it is not classified as a common taxon in any state within its documented distribution. Globally the species is considered to be vulnerable (G3), and a review of state conservation status ranks shows that Hypericum adpressum is classified as either critically im- Page 101 2016 THE MICHIGAN BOTANIST 101 FIGURE 1. Hypericum adpressum in flower in coastal plain marsh near Little Robinson Lake, Man- istee National Forest, Newaygo County, Michigan. Photo by Bradford S. Slaughter. periled (S1) or imperiled (S2) in each of the 15 states where it is considered to be extant (NatureServe 2015). In the remaining five states where this species has been documented, it is known only from historical records (four states) or is con- sidered to be extirpated (one state). In Michigan, Hypericum adpressum is cur- rently ranked as critically imperiled and is protected as a state threatened species (Michigan Natural Features Inventory 2016). Interestingly, when we discovered Page 102 102 THE MICHIGAN BOTANIST Vol. 55 this species, we found it in abundance in an area well-known to, and frequented by, botanists familiar with wetlands known to contain Atlantic Coastal Plain dis- junct species. This forb was discovered at a site within the Manistee National Forest near Little Robinson Lake, in a tract southwest of White Cloud that en- compasses an exemplary wetland complex of high-quality coastal plain marshes, a rare natural community type in Michigan (Cohen et al. 2014). Any of a num- ber of factors may have hampered an earlier discovery of Hypericum adpressum in Michigan, including the highly variable water table fluctuations that can occur in coastal plain marshes both within and between seasons. During high water years, Hypericum adpressum may have been dormant (non-emergent) or sterile and highly reduced in size, and similarly dormant or depauperate during droughty years with protracted drawdowns. This robust species also may have simply been missed as a result of a fortuitous mismatch in the timing of surveys with the flowering period. Our collective experience with the coastal plain marsh community in Michigan, which has included annual plot monitoring in south- west Michigan, has demonstrated that vegetation structure and composition can change markedly from season to season, even when apparently similar habitat conditions persist, thus indicating the need for future research to better under- stand this biologically significant and diverse wetland type. Diagnostic Characters. Hypericum adpressum is a rhizomatous perennial forb about 40-75 cm in height, occasionally having a woody or spongy base, and with opposite, pinnately-veined, linear-oblong leaves that have revolute margins (Voss and Reznicek 2012, Robson 2016, Gleason and Cronquist 1991). The flowers, which are usually numerous and begin to develop in late June to mid- summer, are borne terminally. The sepals are revolute, and the seeds are dis- tinctly less than 1 mm in length (Voss and Reznicek 2012). Hypericum sphaero- carpum (Round-fruited St. John�s-wort), a similar species that can be distinguished by its flat sepals and seeds that are at least 2 mm long, also differs in being a species of dry to somewhat moist upland habitats, and is known in the state from only a single locality in Monroe County in extreme southeastern Michigan. Specimen Citations. Newaygo County: T13N R12W Sec. 19. Lat: 43.504609, Long: -85.800283. Locally common in large coastal plain marshes. With Rhynchospora fusca, Rhynchospora capitellata, Euthamia remota, Pan- icum spretum. Walters and Penskar 9016, Sept. 29, 2005 (MICH). T13N R12W S19. Forms dominant cover in several shallow wetland depressions supporting numerous coastal plain disjuncts. Flowers yellow. Colonies discovered by M. Penskar and B. Walters in 2005. Bradford S. Slaughter 536, July 10, 2006 (MICH). T13N R12W Sec. 19. Large coastal plain marshes near Centerline Rd and 28th St. Locally common, with Calamagrostis canadensis, Euthamia re- mota, Panicum spretum, Rhynchospora capitellata, Rhynchospora fusca. Flowers bright yellow. Walters and Spalink 856, July 19, 2006 (MICH). SW of W 24 Street and Ferris Ave junction, ca. 7 km SW of White Cloud. Lat.: 43� 30. 26.3..N, Long: �85� 50. 03.4..W. Emergent shoreline and shallow water on sandy/peaty shore of small lakes. Abundant, forming dense stands on the shore- line. Flowers yellow, stems with aerenchyma near the base. Reznicek et al. 11833, Aug. 17, 2006 (MICH). Page 103 2016 THE MICHIGAN BOTANIST 103 ACKNOWLEDGMENTS Many thanks to Tony Reznicek, who verified our determination and accompanied us on several further botanical explorations of interesting sites in Newaygo County. We would also like to thank Brad Slaughter for the use of his photo and Michael Huft for edits that greatly improved the manu- script. LITERATURE CITED Cohen, J. G., M. A. Kost, B. 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