Prototype quillwort (Isoetes prototypus) COSEWIC assessment and status report: chapter 8

Limiting Factors and Threats

Brunton and Britton (1993) speculate that the occurrence of I. prototypus in deep, cold, nutrient-poor lakes “may reflect a particularly strict set of site requirements and/or the species’ inability to tolerate significant competition”, and that its distributional potential may be limited by its restrictive habitat requirements. Regardless of the population size at any location, Brunton (pers. com. 2004) cautions that the entire population at each location will only remain extant and viable if the ecological integrity of its supporting aquatic habitat is maintained.   

Lakes where I. prototypus grows often have excellent water quality and are in high demand as sources of drinking water (e.g., sites 1 and 13) or for cottage development and recreation (e.g., sites 4 and 6). Threats to I. prototypus may include direct disturbance of populations or habitat alteration. Plants may be damaged or uprooted by swimming, boating, fishing, the use of anchors, raking swimming areas, the installation of water intake pipes, or the activities of wildlife (Britton and Brunton 1991). At one of the sites, bushels of wrack, comprised largely of plants of I. prototypus, are removed from a 30+ m stretch of beach every year (Britton 2002, pers. com.). Raking and removal of wrack can reduce the reproductive potential of the population. While the extent of this activity may currently be a minor factor involving less than 1% of the shoreline of the lake, it is worth noting its potential effect since floating plants tend to be concentrated in small areas depending upon the wind direction and wave action.

Habitat modifications that could potentially have a negative impact on I. prototypus include cottage and shoreline development, changes in water levels by damming or draining, water pollution, eutrophication, siltation, changes in pH and competition by invasive and/or exotic aquatic plant species (New Brunswick Museum 1994). Aquatic Isoetes species are evidently vulnerable to water pollution (Brunton and Britton 1993).

At sites 1, 2 and 4, roadways and/or causeways border or encroach upon the shoreline at one or more locations.  Cottage development and associated shoreline deforestation were extensive around much of sites 4 and 8, and at one end of sites 6 and 7. It is not known if these disturbances to the surrounding habitat have had any impact on the populations of I. prototypus in these lakes. Further shoreline development is unlikely to occur at two of the three New Brunswick sites (sites 11 and 12).

Wildlife (e.g., moose) has been observed as a source of disturbance, yet the animal species noted at these sites are not new to the landscape and their significance on populations of I. prototypus is unknown.

Although Isoetes prototypus is of great interest to Isoëtologists, the leading researchers on this genus are very concerned about ensuring that this species is not harmed by overzealous collecting and place great importance on its conservation. Unfortunately, this and other Isoetes species can seldom be identified with certainty in the field, and must be collected for identification and verification.

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