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2015 THE MICHIGAN BOTANIST 131
THE FIRST RECORD FOR MICHIGAN OF GALIUM PEDEMONTANUM (RUBIACEAE)
Significance of the Report. The first recorded occurrence in Michigan of this widespread European annual.
Previous Knowledge. The earliest reported collection of Galium pedemon- tanum (Bellardi) All. (Foothills bedstraw) in the United States is from Kentucky in 1933 (Sanders 1976). By 1976, it had already spread to Arkansas, Illinois, Missouri, Ohio, Oklahoma, Tennessee, Virginia, and West Virginia (Sanders 1976). Currently, its distribution includes the additional states of New York, Pennsylvania, North Carolina, South Carolina. Georgia, Mississippi, Louisiana, Texas, Indiana, Nebraska, and the Pacific Northwest states of Washington, Ore- gon, Idaho, and Montana (USDA, NRCS 2015). The nearest location to the one reported here for Michigan is about 23 km south-southeast in St. Joseph County, Indiana (Swink and Wilhelm 1994).
Discussion. Galium pedemontanum, a slender, sprawling, annual plant with retrorsely-barbed stems, was probably an accidental introduction into the flora of the United States. Using collection data from herbarium specimens, Sanders (1976) traced the spread of the species from its first reported locality, showing that it had been transported in all directions from Lexington, Kentucky. Going a step further, Sanders also predicted the future distribution of this species by iden- tifying and using the soil and climate characteristics of its European habitats to delineate similar sites in the USA. In Europe, G. pedemontanum is found where the mean annual temperature is 8–18°C, the mean annual rainfall is 40–150 cm., and the soils, which have developed under forests, are acidic (Sanders 1976). With a mean annual temperature of 7–9°C, a mean annual precipitation of 76–81 cm, and soils mapped as fine sands which are acidic to neutral (USDA, NRCS 2013), the climate and soils of southwestern Michigan are similar to Sanders’ European climate and soils. Interestingly, his map shows southwestern Michigan at one of the northern edges of the potential USA distribution of G. pedemon- tanum.
I spotted the population of Galium pedemontanum, the dozen plants of which were scattered over an area of approximately 2 m2, because the elongated, lax, pale stems stood out against the dark green of the lawn grasses in the middle of summer 2015. In early May 2016, numerous plants, now verdant and semi-erect, were growing in a 25 m2 area at the same location, but now associated with other spring-flowering introduced species (e. g., Scleranthus annuus L., Veronica ar- vensis L., Arenaria serpyllifolia L., Cardamine hirsuta L., Lamium purpureum L., Oxalis stricta Jacq., and Myosotis stricta Roem. & Schult.). Because this lo- cation is close to a road, I suspect that the seeds of G. pedemontanum may have been carried in by vehicle traffic.
Recent studies (e.g., Ehrendorfer and Barfuss 2014) suggest that Galium
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FIGURE 1. Galium pedemontanum at the collection site.
pedemontanum, along with several other Eurasian species, should be segregated as the genus Cruciata. In that case, our species would be known as Cruciata pedemontana (Bellardi) Ehrend.
Diagnostic Characters. Galium pedemontanum is one of only two annual species among the 21 species of Galium now known from Michigan (Voss and
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Reznicek 2012). It is a weak-stemmed, scrambling plant with noticeably scabrous stems. It may be distinguished from the other annual species in Michi- gan, Galium aparine L., by its greenish-yellow flowers with glabrous ovaries and its four small ovate leaves per node, and from Galium verum L., the other yel- low-flowered Michigan bedstraw, by its shorter leaves. Below are the key char- acters that can be used to separate Galium pedemontanum from Galium aparine and from Galium verum.
Galium aparine—leaves 6–8 at each node, 1–8 cm long, flowers greenish white, fruits hispid. Galium pedemontanum—leaves 4 at each node, 3–11 mm long, flowers dull yel- low, fruits glabrous Galium verum—perennial, leaves 4 at each node, 1–5.4 cm long, flowers yellow, fruits glabrous.
Specimen Citation. Michigan, Berrien County, Sawyer (N41° 53.681.; W86° 36.585.). In sandy soil of open lawn with Poa pratensis, Medicago lupulina and Oxalis stricta. July 27, 2015, Tatina s.n. (MICH).
Ehrendorfer, F., and M. H. J. Barfuss. (2014). Paraphyly and polyphyly in the worldwide tribe Ru- bieae (Rubiaceae): Challenges for generic delimitation. Annals of the Missouri Botanical Gar- den 100: 79–88.
Sanders, R. W. (1976). Distributional history and probable ultimate range of Galium pedemontanum (Rubiaceae) in North America. Castanea 41: 73–80. Swink, F., and G. Wilhelm. (1994). Plants of the Chicago region, 4th edition. Indiana Academy of Science. Indianapolis. USDA, NRCS. (2103). Web Soil Survey. Available at www.websoilsurvey.nrcs.usda.gov/. (Accessed May 12, 2016). USDA, NRCS. (2015). The PLANTS database. National Plant Data Team, Greensboro, North Car- olina. Available at plants.usda.gov/core/profile?symbol=CRPE10 (Accessed July 28, 2015). Voss, E. G., and A. A. Reznicek. (2012). Field manual of Michigan flora. The University of Michi- gan Press. Ann Arbor.
——Robert Tatina Dakota Wesleyan University Mitchell, South Dakota 57301 firstname.lastname@example.org