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Recovery Strategy for the False Hop Sedge (Carex lupuliformis) in Canada [Proposed]

1. COSEWIC* Species Assessment Information

Date of Assessment: November 2011

Common Name: False Hop Sedge

Scientific Name: Carex lupuliformis

COSEWIC Status: Endangered

Reason for Designation: In Canada, this rare sedge is found in southern Ontario and Quebec where fewer than 250 mature plants have been found.  There have been substantial historical population losses attributed to residential development and other forms of land use.  Continued declines are attributed to late season flooding, land drainage, invasive alien species, recreation, erosion, garbage deposition, water regime regulation, and residential and urban development.  Recovery efforts have included re-introduction at three sites in Quebec.

Canadian Occurrence: Ontario, Quebec

COSEWIC Status History: Designated threatened in April 1997. Status re-examined and designated endangered in May 2000 and November 2011.

* Committee on the Status of Endangered Wildlife in Canada

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2. Species Status Information

Less than 1% of the global False Hop Sedge (Carex lupuliformis) population is found in Canada (Labrecque, 1998). The species is listed as endangered[1] on Schedule 1 of SARA (S.C. 2002, c. 29). It is listed as threatened[2] in Quebec under the Act respecting threatened or vulnerable species (R.S.Q. c. E-12.01) and as endangered in Ontario under the Endangered Species Act, 2007 (S.O. 2007, c. 6).

In the most recent NatureServe assessment (dating from 2000), the species was assigned a global conservation status rank of G4 (apparently secure), a national rank of N4 (apparently secure) in the United States and N2 (imperilled) in Canada, and a subnational rank of S1 (critically imperilled) in Ontario and Quebec (NatureServe, 2010; see Appendix A for definitions of ranks).

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3. Species Information

3.1 Species Description

Based on COSEWIC (2011) and references cited therein, False Hop Sedge is a perennial herbaceous plant in the Cyperaceae family. This sedge reaches a height between 50 and 130 cm. It grows in tufts comprising 5 to 30 stems arising from a sympodial rhizome[3]. The leaves (i.e., blade) are smooth, erect and 30 to 80 cm long. Flowering begins in late June with an inflorescence[4] 6 to 40 cm across, bearing 1 to 6 elongated spikes. Fruiting occurs from mid-July to late October in Canada. The perigynium (fruit casing) is glossy. The plant’s achenes (one-seeded fruits) are trigonous (have a triangular cross-section). The achenes bear prominent nipple-like knobs, a characteristic that can be used to distinguish False Hop Sedge from Hop Sedge (Carex lupulina), which are otherwise virtually identical during the vegetative stage.

3.2 Population and Distribution

False Hop Sedge is a species with a sporadic distribution in eastern North America and is at the northern limit of its distribution in Canada. Its range in the United States includes all states from Wisconsin, Iowa, Kansas, Oklahoma and Texas eastward to New York. In Canada, it occurs solely in the southernmost part of Ontario and Quebec (Figure 1).

Figure 1: Distribution of False Hop Sedge in North America. Map by Y. Lachance, reproduced with permission of the Ministère du Développement durable, de l’Environnement et des Parcs du Québec (in COSEWIC, 2011).

Figure 1 shows the current distribution of False Hop Sedge in North America (concentrated in south-eastern North America).

According to COSEWIC (2011), the species’ extent of occurrence in Canada is about 23 900 km² (~41 800 km² when including reintroduction sites). This area has declined by about 21 550 km² since the last report (Labrecque, 1998), primarily owing to the extirpation of the populations in the Ottawa River sector in Quebec. When the reintroduction sites are factored in, the reduction is 3 540 km². The species’ current area of occupancy in Canada is less than 0.01 km².

There are 20 populations documented in Canada, 12 of which had naturally-occurring individuals in 2009 or after (Appendix B). In Ontario, all populations are concentrated in Middlesex and Elgin counties. In Quebec, they are located along a 20-km stretch of the Richelieu River, near Saint-Jean-sur-Richelieu, and along a 10-km stretch of the Ottawa River.

In order to increase the resilience of the species, individuals have been transplanted in four of the extant populations (three in Quebec, one in Ontario) and reintroduced in two of the extirpated populations (both in Quebec). The necessity of such measures became evident following the severe flooding of the Richelieu River in Quebec during spring 2011 after which only two naturally-occurring individuals were found (Stéphanie Pellerin, personal communication). Had this species not benefited from reintroduction efforts and augmentation of its numbers by transplantations since 2006, it would have been nearly extirpated in the Province of Quebec today.

In 2009–2010, there were 361 mature individuals (142, if transplants are excluded) in the extant population.  Population size can fluctuate from year to year, and despite recent monitoring of populations, no clear trend is discernable. A number of factors explain this situation. First, the data available prior to 2005 were primarily estimates and based solely on fruiting individuals which vary as a function of hydrological conditions (Letendre et al., 2007). Second, it is almost impossible to identify vegetative (seedless) individuals of the species. Hence, permanent marking of plants is essential for tracking population trends. This approach has been used since 2005 for individuals in Quebec’s populations where more than 180 individuals have been marked[5], and the fluctuations observed indicate a downward trend (see Appendix B).

3.3 Needs of False Hop Sedge

The False Hop Sedge colonizes a transition zone along the natural shorelines of various types of wetland where the vegetation remains sparse due to periodic short-term flooding or ice scouring (COSEWIC, 2011). These types of habitat favour species that prefer high light and, indeed, the vigour of the False Hop Sedge decreases as the canopy becomes more closed (Letendre et al., 2007). According to COSEWIC (2011), False Hop Sedge appears to be less adaptable to different habitats than most riparian species, which could partly account for its rarity.

In Ontario, wetlands that are currently colonized by False Hop Sedge are vernal pools as well as isolated marshes within wooded swamps that are unconnected to any major streams (Labrecque, 1998; COSEWIC, 2011). The wooded swamps within which these habitats are imbedded likely provide dispersal habitat and support the hydrological processes that maintain them (Eric Snyder, OMNR, personal communication). Although False Hop Sedge is found at locations with limited competition from herbaceous and shrubby plants, the most frequently observed companion species are : Bog Hemp (Boehmeria cylindrica), Rice Cutgrass (Leersia oryzoides), Hop Sedge (Carex lupulina), Clearweed (Pilea pumila), Beggarticks (Bidens spp.), Knotweed (Polygonum persicaria), Cocklebur (Xanthium strumarium) as well as Red Ash (Fraxinus pennsylvanica), Red Maple (Acer rubrum) or Silver Maple (Acer saccharinum) (Labrecque, 1998). The soil is composed of a clay loam (Labrecque, 1998).

In Quebec, False Hop Sedge has only been observed in Silver Maple swamps or shrub swamps in small isolated bays that are sheltered from currents but near a natural shoreline subjected to periodic flooding of short duration. Companion species include Red Ash, Black Willow (Salix nigra), Reed Canary Grass (Phalaris arundinacea), Bog Hemp, Rice Cutgrass, Water Parsnip (Sium suave), Prairie Cordgrass (Spartina pectinata) and Hop Sedge. Except in the case of the Lacolle population, which is located 50 m from a river, the tufts are very close to water (10-15 m) during low flow periods. The soil is composed of a gleysol[6] of recent alluvia ranging from sandy loam to clay loam (Labrecque, 1998) and is poorly drained (COSEWIC, 2011).

The preceeding habitat descriptors and species associations are based on a subset of sites occupied by the species and may not necessarily represent conditions that are optimal for this species that has a very limited distribution in Canada and is at the northern limit of its distribution. The actual distribution of the species could, in certain instances, be the result of historical artifacts related to landscape development.

A persistent seed bank (Templeton and Levin, 1979) plays a crucial role in maintaining False Hop Sedge populations. Aside from the fact that the seeds are dispersed primarily by water, little is known about seed dispersal dynamics. It is nonetheless likely that mature seeds fall into the water and are carried over long distances during flooding, thereby ensuring local dispersal (Labrecque, 1998) and colonization of suitable habitats that become available (COSEWIC, 2011). Despite this, it is assumed that no genetic exchange takes place between the Ontario and Quebec populations since they are hydrologically isolated (COSEWIC, 2011).

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Footnotes

1 Endangered : A species facing imminent extirpation or extinction in Canada.

2 Threatened : A species for which extinction is imminent.

3 Refers to the way the stems develop successively and are joined together along the root.

4 The flowering part of a plant.

5 In Quebec, all naturally-occurring and transplanted individuals are currently marked. For transplanted individuals, stakes are removed after three years of absence whereas stakes are never removed for naturally-occurring individuals (Stéphanie Pellerin, personal communication).

6 [Soils of Canada]