Rare Species Guide

  Synonyms

Eleocharis olivacea

  Basis for Listing

Eleocharis flavescens var. olivacea is characteristic of wetland habitats on the Atlantic Coastal Plain, but also occurs inland where it is considered rare or endangered. This species is apparently absent from large areas of seemingly suitable habitat. Because it is small, inconspicuous, and bears a superficial resemblance to other more common species, it may be inadvertently overlooked and therefore undercollected. As of 2008, there were 10 Minnesota records for this species. Herbarium collections from Todd and Clearwater counties date from the 1930s and the current status of these populations is unknown. An E. flavescens var. olivacea population in Itasca County was discovered in 1977 in Botany Bog, whose name refers to the large assemblage of rare plant species it supports. However, this site was flooded by beaver activity in 1979 and it is unknown what long-term impact this may have on the survival of these rare species. Seven additional locations have been found through Minnesota County Biological surveys in Aitkin, Becker, Cass, Itasca, and Pine counties. Eleocharis flavescens var. olivacea was listed as a threatened species in Minnesota in 1984.

  Description

Eleocharis flavescens var. olivacea is a short, stocky, tufted species that can be reliably identified by the achenes (seeds). They are biconvex with a 2-cleft style, olive to dark brown in color, and have overtopping bristles. The tubercle at the top of the achene is saucer-shaped with a conical center. The scales that subtend the achenes are ovate and round-tipped, with a prominent green midrib and sides that are brown to reddish in color.

  Habitat

Eleocharis flavescens var. olivacea exhibits a preference for shoreline habitats, where substrates may include peat, sand, silt, or mud. Plants may occur in several centimeters of water or stranded above the water line. Habitats have been described as along edges of small bog pools, on floating mats, in a bog dominated by Chamaedaphne calyculata (leatherleaf) and Carex spp. (sedges), a muddy shore of a peatland pond, and a mucky lakeshore in a mixed forest. One record is from the mucky edge of a beaver channel in a bog, appearing to be in the traffic pattern of beaver activity. The largest population of E. flavescens var. olivacea found to date occurs on the black, silty, saturated masses of bog material floating at the water surface along a boggy shoreline. Associated species may include Potamogeton bicupulatus (snailseed pondweed), P. amplifolius (large-leaved pondweed), Myriophyllum farwellii (Farwell's water milfoil), Scirpus subterminalis (swaying bulrush), Pogonia ophioglossoides (rose pogonia), Polygonum amphibium (water smartweed), and Megalodonta beckii (Beck's water-marigold). Utricularia gibba (humped bladderwort) was an associated species in at least 4 of the 10 known sites.

  Biology / Life History

It is unknown if beaver activity is detrimental, beneficial, or neutral in the life history of E. flavescens var. olivacea. Plants may gain a tenuous, and perhaps brief, foothold in areas where beavers have reduced the competition, but continued beaver activity may be detrimental in the long-term.

The best time to search for E. flavescens var. olivacea is July through mid-October.

  Conservation / Management

Eleocharis flavescens var. olivacea is a short-lived opportunist that takes advantage of small gaps and ecotones in wetland vegetation. Such gaps are always appearing and shifting in dynamic, fully functioning wetland communities. Important ecosystem processes that maintain this complex mosaic of habitats include the seasonal rise and fall of water levels, aquatic animal activities, windstorms, insect outbreaks, ice formation and movement, and sedimentation, just to name a few. All conservation and management considerations should make it a priority to maintain or restore these ecosystem functions. Human impacts on wetlands such as salt pollution, nutrient enrichment, pesticide inflows, stormwater storage, and mosquito control can inhibit or nullify natural functions, and should be directed away from healthy, natural wetlands. Monitoring of the Botany Bog site in Itasca County needs to continue to assess the long-term impacts to E. flavescens var. olivacea and other rare plants following the 1979 beaver induced flood.

  Conservation Efforts in Minnesota

No specific conservation efforts have been undertaken on behalf of this species.

  References and Additional Information

Schuyler, A. E. 1977. Chromosome observations on some eastern North American Eleocharis (Cyperaceae). Brittonia 29:129-133.

Smith, S. G., J. J. Bruhl, M. S. Gonzalez-Elizondo, and F. J. Menapace. 2002. Eleocharis. Pages 60-120 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York, New York.

Smith, W. R. 2018. Sedges and rushes of Minnesota: the complete guide to species identification. University of Minnesota Press, Minneapolis. 696 pp.