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Recovery Strategy for the Engelmann's Quillwort (Isoetes engelmannii) in Canada (Proposed)

1.0 Background

Engelmann's quillwortis an aquatic member of a large group of fern allies of the family Isoetaceae (with 300 or more species worldwide); they are primitive plants with a long fossil history. Engelmann's quillwort is endemic to eastern North America. This plant israrely common over a large area; however, they are often locally abundant in their scattered occurrences. Globally, Engelmann's quillwort is listed as G4 (globally widespread and apparently secure) (NatureServe, 2004). Nationally, it is listed as Endangered under the Species at Risk Act (SARA). Provincially, in Ontario, it is listed as S-1 (extremely rare). Progress is currently underway to have it provincially listed as endangered and regulated. This species is also listed as endangered in a number of American states; however, is not listed federally (Figure 1).

Figure 1. Engelmann's Quillwort status in North America (Copyright © 2005 NatureServe, 1101 Wilson Boulevard, 15th Floor, Arlington Virginia 22209, U.S.A. All Rights Reserved; NatureServe. 2005. NatureServe Explorer: An online encyclopedia of life [web application]. Version 4.6. NatureServe, Arlington, Virginia)
Figure 1. Engelmann's Quillwort status in North America (Copyright © 2005 NatureServe, 1101 Wilson Boulevard, 15th Floor, Arlington Virginia 22209, U.S.A. All Rights Reserved; NatureServe. 2005. NatureServe Explorer: An online encyclopedia of life [web application]. Version 4.6. NatureServe, Arlington, Virginia)

1.1 Description

Engelmann's quillwort is a shallow water species generally growing in borders of ponds, lakes and reservoirs, as well as creeks and rivers. This species is frequently found growing as an emergent in the dry season in damp ground or in dry bogs and swamps, in mud, sand, and gravel, within the major part of its distributional range. It is an inconspicuous perennial plant with simple, grass-like leaves. The leaves are usually less than 20 cm long, are green to yellow-green in colour, erect and usually soft. Engelmann's quillwort is very similar in appearance to other species of quillwort with which it is often found.

1.2 Distribution

Engelmann's quillwort was first discovered in Ontario at the Gull River of Haliburton County in 1988 and the Severn River of the District Municipality of Muskoka (Britton et. al. 1991). Its range is limited, confined to a 4.5 km section of the Severn River and about a 450 m section of the Gull River at West Guilford (Figure 2). Engelmann's quillwort plants have not been seen on the Simcoe County side of the Severn River; although, the presence of large sub-populations of Eaton's quillwort (Isoetes x eatonii Dodge), its sterile hybrid with the Spiny quillwort, indicates that it almost certainly persists there (Brunton 2003). Eaton's quillwort was first collected at Big Chute in 1980 (Kott and Bobbette 1980). The robust nature (large plant size and leaf number) of the hybrid makes this taxon the most conspicuous Isoetes at such Canadian Engelmann's quillwort sites.

The Canadian populations of Engelmann's quillwort are disjunct from the North American range of the species. It is believed that this distribution is related to dramatically different drainage patterns that existed in the Great Lakes Region of North America following the end of the Wisconsin glaciation (Chapman and Putnam 1984). This distribution is shared by a suite of shoreline and aquatic species, which are disjunct from their primarily Atlantic Coastal Plain range (Keddy and Sharpe 1989; Britton et. al. 1991; Reznicek 1994).

Review of the possibility that Engelmann's quillwort was accidentally introduced by human activity (e.g. recreational boat traffic) was a major consideration of recent field investigations within the Canadian range (Brunton 2003) and is one of the subjects of on-going molecular studies (Wilson 2004). It is concluded from the field studies that the strongest evidence points to a native origin for both Canadian populations. Evidence includes the fact that the Canadian distribution of Engelmann's quillwort is consistent with that of a significant number of other native aquatic species typical of the Atlantic Coast plain that are rare in Ontario and/or Canada. Further, the abundance of Engelmann's quillwort along the Severn River fits well within the 'Mill Pond scenario', which was first described in new England, where large populations developed locally some decades after the creation of additional aquatic habitat from the flooding by mill pond construction over smaller, indigenous quillwort populations (Eaton 1900). Over time, such populations decline in number, remaining in scattered, smaller sub-populations at particularly suitable sites within the locally expanded range. Such Mill Pond scenarios are known to occur with Engelmann's quillwort populations in at least North Carolina, Pennsylvania, New Hampshire, and New York (Brunton, per. obs.). Finally, there is no known evidence or documentation of Engelmann's quillwort(or any aquatic quillwort species) being inadvertently transported in the wild in North America, let alone over such great distances.

Although not confirmed, it is not expected that Engelmann's quillwort was ever substantially more common in Canada in historic times, as its national distribution is quite similar to that of other coastal disjunct vascular plants, which also maintain small, localized populations in the Great Lakes Region. Less than one percent of the global population of this species is found within Canada.

Outside of Canada, Engelmann's quillwort is most abundant in fresh water lakes and rivers along the Atlantic coastal plain in the eastern United States, and extending westward into the Mississippi River drainage. The previously known distribution of Engelmann's quillwort is described as New England south to southern Georgia and Alabama and west to Missouri (Kott and Bobbette 1980; Kott and Britton 1983). However, population levels in the United States have declined and the species is now extirpated from many historical sites, particularly in New England, Missouri, Georgia, and South Carolina. Presently, the central core of its range is in Virginia, southernPennsylvania and western North Carolina.

1.3 Population size and trends

In Canada, on-site surveys of about 120 potential sites along the Severn River and the Gull River from 2002-2005 identified seven populations of Engelmann's quillwort. On the Severn River, the overall population size for Engelmann's quillwort is currently estimated to be 1094 individuals (Heydon and Pidgen, 2005). In the Gull River the population estimate is 375 individuals (Heydon, 2006). During the same studies, 19 populations of the hybrid between Engelmann's quillwort and Spiny quillwort (Eaton's quillwort) were identified. The occurrence of Eaton's quillwort is taken as confirmation of the presence of Engelmann's quillwort (Figures 3 and 4) since the sterile hybrids have virtually always been found only in the presence of both parents (Brunton and Britton 1999, Brunton 2003). Therefore, the actual number of individuals of Engelmann's quillwort is most likely higher than that estimated above.

Population trends are not known for Canadian Engelmann's quillwort, though at least one formerly large population in the Severn River has been reduced since the early 1990s, apparently as a result of physical site impact such as mechanical damage, wave action, and/or abnormally high rates of sedimentation (Brunton, pers. obs.). Engelmann's quillwort populations have declined throughout the northern portion and western portions of its North American range over the last century (Taylor et. al. 1993).

Figure 2. The known Canadian locations of Engelmann's quillwort (Isoetes engelmannii).
Figure 2. The known Canadian locations of Engelmann's quillwort (Isoetes engelmannii)

1.4 Biology and Ecology

Engelmann's quillwort is a sexual diploid, which produces viable spores, as indicated by the abundance of its hybrid with Spiny quillwort. Vegetative reproduction has not been reported for any of the Isoetes species of North America. Canadian plants of Engelmann's and Eaton's quillwort have mature megaspores by early August. Plants of shallower water likely mature at an earlier date than those in deeper water. Dispersal of spores begins when the sporangium is ruptured, either by physical impact or by decay at the end of the growing season. The frequency of dense stands suggests that spores are often dispersed only a short distance, or may be carried downstream on buoyant detached leaves. Spores probably concentrate downstream in back-eddies and other slow-water areas. Sporophytes develop in such habitats following the contact of microspores with megaspores and can do so even in dynamic habitats (e.g. developing on sand spits in flowing river waters). This development presumably occurs during the late summer and fall period. Spore germination and vernalization requirements in reference to survival and distribution of Isoetes species have been discussed in Ontario, including Engelmann's quillwort (Kott and Bobbette 1980; Kott and Britton, 1982).

There appear to be few natural predators of Engelmann's quillwort perhaps in part, because they typically grow in rather sterile environments (i.e. not nutrient rich). Waterfowl and muskrats feed upon and dislodge fully developed plants; however, it is not clear if such events are common or have a direct effect on species distribution.

1.5 Habitat

All Canadian populations of Engelmann's quillwort are found in similar aquatic habitats characterized by fresh, flowing, circumneutral to calcareous water and substrate (pH 6.0 - 8.1). Sites are typically protected from heavy river currents and wave action by an intervening headland, island, etc. While typically submerged, Engelmann's quillwort can also be found as a late summer emergent of wet, silty beaches amongst boulders, occasionally in association with other Isoetes species. Backshore vegetation consists of mixed and deciduous forest cover. The Haliburton County population is partially shaded whereas the Severn River population in the District Municipality of Muskoka and the Simcoe County populations of I. ×eatonii grow in full sunlight.

Plants are found in a sand or silty-sand layer over clay or clayey-sand substrate. These are often within a dense granitic cobble bed but occur on open, relatively rock-free river sediment as well. Common associated species include Eel-grass (Vallisneria americana), Spiny quillwort (Isoetes echinospora), Najad (Najas flexilis), waterweed (Elodea canadensis), pondweeds (Potamogeton illinoensis, P. pectinatus, P. natans), grassleaf arrowhead (Sagittaria graminea), and crested arrowhead (Sagittaria cristata). The latter, a Provincially Rare Great Lakes endemic, appears to be as common as grassleaf arrowhead in the habitats of the Severn River Engelmann's quillwort sites.

The ecological flexibility of the Engelmann's quillwort might be limited. While Engelmann's quillwort can be maintained in cultivation for years in a standing pot of water, it is almost never found in nature in still, warm water. The fact that this species is found upstream of the Big Chute dam does indicate, however, that it can adapt to water level fluctuations. Water levels increased approximately 3.0 m with the construction of the dam in 1917, and it is interesting to note that Engelmann's quillwortis found in a number of sites upstream (but not downstream) of the dam.

The Haliburton County population is situated along an essentially natural section of the Gull River, where the water level is regulated, although not significantly. The habitat of this population looks very similar to that of a number of small-stream Engelmann's quillwort populations in Virginia and New Hampshire (Brunton pers. obs.). Water flows are controlled by a dam at the outlet of Eagle Lake, upstream of the Gull River population. Water levels fluctuate approximately 1 m annually at the outlet of Maple Lake, which is downstream of the population. This section of the river is also not suitable for navigation by large pleasure boats, which could have cruised continuously from areas of Engelmann's quillwort occurrences, thus reducing the opportunity for the transport of live plant material.