Rough-leaved Aster (Eurybia radulina): COSEWIC assessment and status report 2024

Official title: COSEWIC assessment and status report on the Rough-leaved Aster (Eurybia radulina) in Canada

Committee on the status of Endangered Wildlife in Canada (COSEWIC)

Threatened

2024

 

COSEWIC assessment summary

Assessment summary – May 2024

Common name

Rough-leaved Aster

Scientific name

Eurybia radulina

Status

Threatened

Reason for designation

This herbaceous perennial occurs on southeast Vancouver Island, British Columbia where it reaches its northern range limit in North America. In Canada, it reproduces primarily by underground rhizomes and often presents only as rosettes of leaves. The species is known from only five subpopulations within a small range of 260 km², with only 330 known flowering stems and 788 non-flowering stems in total. Declines are suspected based on changes in the area, extent, and quality of habitat. The Wildlife Species may be negatively impacted both by maintenance activities along transportation corridors and invasive species in its habitat; it may also be limited by the absence of mature flowering individuals in some subpopulations.

Occurrence

British Columbia

Status history

Designated Threatened in May 2024.

COSEWIC executive summary

Rough-leaved Aster

Eurybia radulina

Wildlife species description and significance

Rough-leaved Aster is a long-lived, showy perennial herb. The thick leaves have sharp teeth along the margins and the flowers, which are pale violet with yellow centres, are grouped in flat-topped clusters.

Aboriginal (Indigenous) knowledge

All species are significant, interconnected and interrelated. There is no species-specific Aboriginal Traditional Knowledge in the report.

Distribution

In Canada, Rough-leaved Aster is at the northern limit of its distribution. The species is found on southeastern Vancouver Island in British Columbia. In the United States, it extends south through Washington, Oregon and California, primarily occurring west of the Cascade Range.

Habitat

In British Columbia, Rough-leaved Aster is found in mixed Douglas-fir, Garry Oak, Arbutus and Shore Pine forests with partial canopy closure, in the Coastal Douglas-fir biogeoclimatic zone. Sites containing the species are moderately moist, with moderately rich soils, at elevations of 60 to 427 m above sea level. The composition of the vegetation understory is variable, with most sites having some shrub cover. All known subpopulations are next to trails or roads.

Biology

Rough-leaved Aster is a herbaceous perennial that reproduces by seed and spreads by underground rhizomes. Flowering occurs from June through August, but is sparse and infrequent in three of the five subpopulations. On the basis of studies of similar species in the subtribe Astereae, flowering likely occurs the second year following germination. Fecundity is unknown. It is presumed, based on studies of closely related species, that Rough-leaved Aster is primarily an outbreeding species. Germination and seedling establishment have not been observed in the wild in Canada.

Population sizes and trends

Surveys in 2022 of all known subpopulations in Canada documented five extant subpopulations containing a total of 330 flowering shoots and 788 non-flowering shoots. Shoots are connected by underground rhizomes and the number of separate individuals is not known. Prior estimates of subpopulation sizes suggest that the population is stable, although historical subpopulations may have been destroyed due to habitat conversion. The species is presumed to be long-lived and, in the absence of habitat destruction, the population is expected to be stable over time.

Threats

The overall threat impact to Rough-leaved Aster is Medium – Low. Threats to the species include the presence of the invasive shrub Scotch Broom, which casts shade; alters vegetation structure; changes the soil chemistry to create more favourable conditions for other invasive species; and limits pollinator movement, resulting in decreased seed set. Non-native grasses compete with Rough-leaved Aster for light and moisture. Two subpopulations occur next to paved roads, where mowing and other maintenance activities may limit sexual reproduction. Fires and fire suppression (including the use of fire retardants) may impact Rough-leaved Aster, and human-caused fires are possible in the subpopulations, especially in the two next to roads. Two subpopulations may be impacted by land-use changes associated with activities by private landowners or the B.C. Ministry of Transportation and Infrastructure (MOTI). The impacts of earthquakes, droughts, temperature extremes and extreme rainfall events are unknown.

Protection, status, and recovery activities

Rough-leaved Aster was assessed by COSEWIC as Threatened in May 2024 and is not listed under the Species at Risk Act. NatureServe ranks Rough-leaved Aster as nationally Imperilled (N2) in Canada, and as Secure (G4G5) globally. Rough-leaved Aster is ranked as Imperilled (S2) in British Columbia and is thus on the province’s Red List. Among the five extant Canadian subpopulations, three are in regional parks, where they are protected from development. In the United States, the species is Unranked (NNR) nationally, and at the state level in Washington, Oregon and California.

Technical summary

Eurybia radulina

Rough-leaved Aster

Aster râpette

Range of occurrence in Canada: British Columbia

Demographic information:

Generation time (usually average age of parents in the population)

Estimate 10+ years

Estimate based on lifespan and age to maturity of similar species in the subtribe Astereae

Is there an [observed, estimated, inferred, or projected] continuing decline in number of mature individuals?

Unknown

Based on previous estimates of subpopulation sizes (all in the last 10 years), the number of mature individuals in extant subpopulations appears stable. Increases in two subpopulations are due to finding additional sites. There has been no long-term monitoring to determine population trends and no consistent recounts of known subpopulations.

[Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 3 years [or 1 generation; whichever is longer up to a maximum of 100 years]

Unknown

No long-term monitoring has been done to determine population trends and there have been no consistent recounts of known subpopulations. All previous estimates of subpopulation sizes are from the last 10 years.

Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 5 years [or 2 generations; whichever is longer up to a maximum of 100 years]

Unknown

No long-term monitoring has been done to determine population trends and there have been no consistent recounts of known subpopulations. All previous estimates of subpopulation sizes are from the last 10 years.

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last 10 years [or 3 generations; whichever is longer]

Unknown

No long-term monitoring has been done to determine population trends and there have been no consistent recounts of known subpopulations. All previous estimates of subpopulation sizes are from the last 10 years.

[Projected, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations, up to a maximum of 100 years]

Unknown

No long-term monitoring has been done to determine population trends and there have been no consistent re-counts of known subpopulations. All previous estimates of subpopulation sizes are from the last 10 years.

[Observed, estimated, inferred, projected, or suspected] percent [reduction or increase] in total number of mature individuals over any period of 10 years [or 3 generations; whichever is longer, up to a maximum of 100 years], including both the past and future (up to a maximum of 100 years in future)

Unknown

Status of historical subpopulations unknown due to imprecise locality data. All previous estimates of subpopulation sizes are from the last 10 years.

Are the causes of the decline clearly reversible?

Unknown

Not applicable

Are the causes of the decline clearly understood?

Unknown

Possible loss of historical subpopulations due to habitat destruction

Are the causes of the decline clearly ceased?

Unknown

Not applicable

Are there extreme fluctuations in number of mature individuals?

Unknown

No long-term monitoring has been done to determine population trends and there have been no consistent recounts of known subpopulations. Previous subpopulation estimates in the last 10 years suggest the number of mature individuals does not fluctuate by orders of magnitude.

Extent and occupancy information:

Estimated extent of occurrence (EOO)

260 km²

Calculated based on minimum convex polygon around known occurrences based on data collected in 2022

Index of area of occupancy (IAO), reported as 2x2 km grid value

20 km²

Based on data collected in 2022

Is the population “severely fragmented”, that is, is >50% of individuals or >50% of the total area “occupied” (as a proxy for number of individuals) in habitat patches that are both (a) smaller than required to support a viable subpopulation, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

1. Unknown
2. Unknown

1. Persistence of plants in many subpopulations since they were first recorded suggests habitat patches may be of sufficient size to support viable subpopulations
2. There appears to be suitable contiguous habitat next to existing subpopulations

Number of “locations” (use plausible range to reflect uncertainty if appropriate)

6

Number of locations is based on the number of subpopulations (5) along with the land ownership/management at each, as different land managers may make different management decisions impacting the species or its habitat.

Is there an [observed, inferred, or projected] continuing decline in extent of occurrence?

Unknown

Status of historical subpopulations unknown due to imprecise locality data

Is there an [observed, inferred, or projected] continuing decline in area of occupancy?

Unknown

Status of historical subpopulations unknown due to imprecise locality data

Is there an [observed, inferred, or projected] continuing decline in number of subpopulations?

Unknown

Status of historical subpopulations unknown due to imprecise locality data

Is there an [observed, inferred, or projected] continuing decline in number of “locations”?

Unknown

Status of historical subpopulations unknown due to imprecise locality data

Is there an [observed, inferred, or projected] continuing decline in [area, extent and/or quality] of habitat?

Possibly

Suspected decline in area, extent and quality of habitat due to invasive species

Are there extreme fluctuations in number of subpopulations?

No

Inferred stable number of subpopulations (excluding historical subpopulations)

Are there extreme fluctuations in number of “locations”?

No

Inferred stable number of locations (excluding historical locations)

Are there extreme fluctuations in extent of occurrence?

No

Inferred stable EOO (excluding historical subpopulations)

Are there extreme fluctuations in index of area of occupancy?

No

Inferred stable IAO (excluding historical subpopulations)

Number of mature individuals (by subpopulation):

Quantitative analysis:

Is the probability of extinction in the wild at least 20% within 20 years [or 5 generations], or 10% within 100 years]

Unknown

Analysis not conducted

Threats

Was a threats calculator completed for this species?

Yes (see Appendix A)

Overall assigned threat impact:

Medium – Low (2023)

Key threats were identified as:

1. Natural System Modifications: Other Ecosystem Modifications (IUCN #7.3; Medium – Low)
2. Natural System Modifications: Fire and Fire Suppression (IUCN #7.1; Low)
3. Transportation and Service Corridors: Roads and Railroads (IUCN #4.1; Unknown)
4. Pollution: Domestic and Urban Waste Water (IUCN #9.1; Unknown); Agricultural and Forestry Effluents (IUCN #9.3; Unknown)
5. Invasive and Other Problematic Species, Genes and Diseases (IUCN #8.1: Unknown) (IUCN #8.2: Unknown)
6. Climate Change and Severe Weather (IUCN #11; Unknown)

What limiting factors are relevant?

• Lack of reproduction in most subpopulations
• Possible genetic limitations associated with self-incompatibility, clonal growth and small, fragmented populations

Rescue effect (from outside Canada):

Status of outside population(s) most likely to provide immigrants to Canada.

Stable

Populations outside of Canada are abundant and unranked. The closest confirmed extant occurrence is approximately 250 km away in Washington.

Is immigration known or possible?

Unknown

Unlikely, because dispersal distances are large and immigration would involve crossing the Strait of Juan de Fuca

Would immigrants be adapted to survive in Canada?

Unknown

Probably yes, because habitat conditions in the U.S. are similar to those in Canada

Is there sufficient habitat for immigrants in Canada?

Unknown

The habitat requirements in Canada do not appear to be highly specialized. Habitat that appears to be suitable is extensive on southern Vancouver Island.

Are conditions deteriorating in Canada?

Yes

There have been marked declines in habitat extent and quality in the Coastal Douglas-fir biogeoclimatic zone.

Are conditions for the source (that is, outside) population deteriorating?

Unknown

Unlikely, because the population in the U.S. is not at risk

Is the Canadian population considered to be a sink?

No

Large dispersal distances to Canada do not create sink conditions.

Is rescue from outside Canada likely, such that it could lead to a change in status?

No

Unlikely, due to large dispersal distances over a large body of water

Wildlife species with sensitive occurrence data (general caution for consideration):

Could release of certain occurrence data result in increased harm to the Wildlife Species or its habitat?

No

Status history:

COSEWIC

Designated Threatened in May 2024

Status and reasons for designation:

Status

Threatened

Alpha-numeric codes

D1

Reason for change in status

Not applicable

Reasons for designation

This herbaceous perennial occurs on southeast Vancouver Island, British Columbia where it reaches its northern range limit in North America. In Canada, it reproduces primarily by underground rhizomes and often presents only as rosettes of leaves. The species is known from only five subpopulations within a small range of 260 km², with only 330 known flowering stems and 788 non-flowering stems in total. Declines are suspected based on changes in the area, extent and quality of habitat. The Wildlife Species may be negatively impacted both by maintenance activities along transportation corridors and invasive species in its habitat; it may also be limited by the absence of mature flowering individuals in some subpopulations.

Applicability of criteria:

A: Decline in total number of mature individuals:

Not Applicable.

Insufficient data to reliably infer, project or suspect population trends

B: Small range and decline or fluctuation

Not applicable.

May meet Threatened, B1ab(iii)+2ab(iii). The EOO of 260 km² and IAO of 20 km² are below the threshold for Endangered. The population occurs in five subpopulations representing six threat-based locations, which is below the threshold for Threatened; however, continuing decline in area, extent and quality of habitat is only suspected, not observed, inferred or projected.

C: Small and declining number of mature individuals

Not applicable.

Does not meet Threatened, C2a(i) or Endangered, C2a(ii); although the number of mature individuals is well below the thresholds, there is insufficient information to determine whether there is a continuing decline in mature individuals.

D: Very small or restricted population

Meets Threatened, D1.

Meets Threatened, D1, as the number of mature individuals is estimated to be fewer than 1,000. Threatened, D2, is not applicable as the population is not vulnerable to rapid and substantial decline.

E: Quantitative analysis

Not applicable.

Analysis not conducted

If a species is proposed as Special Concern, Data Deficient, Extirpated or Extinct, list the applicable guidelines, examples, or other considerations from O&P Appendix E3.

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2024)

Wildlife Species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)^*

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)^**

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)^***

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

^* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
^** Formerly described as “Not In Any Category”, or “No Designation Required.”
^*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.

Wildlife species description and significance

Name and classification

Current classification: Eurybia radulina (A. Gray) G.L. Nesom

Class: Magnoliopsida

Order: Asterales

Family: Asteraceae

Subfamily: Asteroideae

Tribe: Astereae

Genus: Eurybia

Species: Eurybia radulina

Subspecies in Canada: none

Common names:

English: Rough-leaved Aster, Rough-leaved Wood Aster (VasCan 2022), Roughleaf Aster (Brouillet 2006)

French: aster râpette (VasCan 2022)

Synonyms and notes:

Aster eliasii A. Nelson, Aster radulinus A. Gray, Weberaster radulinus (A. Gray) Á. Löve and D. Löve (Brouillet 2006; VasCan 2022)

Eurybia was classified within the genus Aster prior to the review of North American asters by Nesom (1994). The separation of these genera is supported by molecular phylogenetic studies (Semple et al. 2002 in Brouillet 2006). There are 22 species in the genus, and they are predominantly found in eastern North America (Semple 2014). Rough-leaved Aster is diploid and appears to be closely related to eastern Eurybia species (Selliah and Brouillet 2008).

Description of wildlife species

Rough-leaved Aster is a robust perennial herb that grows to 10 to 70 cm tall from a slender rhizome (Figure 1). The stems are covered with long hairs. The leaves are opposite and 4 to 13 cm long, with sharp teeth along the margins and a rough surface (Figure 2). The inflorescence is a flat-topped cluster with 5 to 30 floral heads. In Canada, the ray flowers are pale violet and the disc flowers, yellow (Figures 3 and 4), although the latter are whitish in some U.S. populations (Brouillet 2006; Calflora 2023). The involucre bracts below the flowers have distinct phyllaries with a strong midrib and purple margins (Figure 4). The seeds are grooved achenes covered in stiff hairs and are wind dispersed by a pappus (Figure 5) (Douglas et al. 1998; Brouillet 2006).

Figure 1. Image of Rough-leaved Aster from Douglas et al. 1998. Used courtesy of the Royal BC Museum.

Figure 2. Non-flowering shoot of Rough-leaved Aster. Photo: C. Maslovat (July 7, 2022, Thetis Lake Regional Park, View Royal).

Figure 3 Aster râpette. Photo prise par C. Maslovat à 180 m au nord de la rivière Cowichan, à l’ouest de Duncan.

Figure 4. Close-up of flowers of Rough-leaved Aster. Photo: R. Batten (July 31, 2013, Dr. Hans Roemer’s garden, grown from rhizomes collected on Mount MacDonald, Vancouver Island).

Figure 5. Seeds of Rough-leaved Aster, showing the pappus on each. Photo: R. Batten (January 23, 2022).

Designatable units

Rough-leaved Aster occurs in a very restricted geographic area, and there is no information to suggest the existence of discrete or evolutionary significant groups of individuals in the Canadian population that should be recognized as designatable units. The occurrence of Rough-leaved Aster in Canada is considered one designatable unit.

Special significance

Rough-leaved Aster is a showy species and, in the central part of its range in the United States, is grown by nurseries for use in butterfly and bee gardens (California Native Plant Society 2022; Regan Biological and Horticultural Nursery 2023). In Canada, it is at the northern limit of its distribution, and is likely used by pollinators.

Aboriginal (Indigenous) knowledge

Aboriginal Traditional Knowledge (ATK) is relationship-based. It involves information on ecological relationships between humans and their environment, including characteristics of species, habitats and locations. Laws and protocols for human relationships with the environment are passed on through teachings and stories, and Indigenous languages, and can be based on long-term observations. Place names provide information about harvesting areas, ecological processes, spiritual significance or the products of harvest. ATK can identify the life history characteristics of a species or distinct differences between similar species.

Cultural significance to Indigenous peoples

There is no species-specific ATK in the report. However, Rough-leaved Aster is important to Indigenous Peoples, who recognize the interrelationships of all species within the ecosystem.

Distribution

Global range

Rough-leaved Aster is found from Vancouver Island in British Columbia, south through the U.S. states of Washington and Oregon, and into the southern Coast Range mountains, northern Channel Islands and central Sierra Nevada range of California (Figure 6). It occurs primarily west of the Cascade Mountains (Brouillet 2006).

Figure 6. Global distribution of Rough-leaved Aster. Map prepared by A. Filion, Scientific and GIS Project Officer, Environment and Climate Change Canada, Gatineau, QC. Locality data for the United States from Global Biodiversity Information Facility (GBIF 2022).

Canadian range

The historical range of Rough-leaved Aster in Canada extends from Horne Lake (west of Qualicum Beach) south to Mount Braden (Langford) on southeastern Vancouver Island. The status of the northern subpopulations is unknown due to imprecise locality data. However, given the pervasive land alteration and development on Vancouver Island, it is unlikely that these subpopulations persist, and therefore they are considered historical. The most northerly confirmed subpopulation is in the Cowichan Valley west of Duncan (Figure 7). Less than 1% of the global population occurs in Canada, and the Canadian subpopulations are about 250 km disjunct from the closest occurrence in the United States (a historical record from Orcas Island, U.S., Beattie 1909 WS 30600).

Figure 7. Canadian distribution of extant and historical Rough-leaved Aster occurrences. Map prepared by A. Filion, Scientific and GIS Project Officer, Environment and Climate Change Canada, Gatineau, QC.

Biology and habitat use

Life cycle and reproduction

Published information on the biology and ecology of Rough-leaved Aster is limited. The information presented below is compiled primarily from research on other species in the subtribe Astereae, the report writers’ personal observations and grey literature.

Rough-leaved Aster is a herbaceous, somewhat woody, perennial that reproduces from seed and spreads by underground rhizomes. It is propagated for horticulture both from seeds and from pieces of the root crown (Lady Bird Johnson Wildflower Center 2023).

Plants flower from June through September in the central part of its range, in the U.S. (Brouillet 2012; Lady Bird Johnson Wildflower Center 2023). In three of the subpopulations in Canada (Thetis Lake Regional Park, Mt. MacDonald and Mt. Braden), flowering is sparse and infrequent. From 1969 to 1974, no flowers were observed in either the Francis/King Regional Park or Thetis Lake Regional Park subpopulations; however, material that was collected and potted up from three separate sites in 1973 bloomed from June through August of the following year (Armstrong and Armstrong 1974). Vegetative samples collected from Mt. MacDonald and Francis/King Regional Park have been successfully cultivated in containers for several years, but viable seed has not yet been collected (Miskelly pers. comm. 2023; Figure 4). Flowering occurs regularly in the two roadside subpopulations (Francis/King Regional Park and Cowichan River), presumably because of the higher light levels.

There is no published information available on age at sexual maturity or longevity in Rough-leaved Aster. An expert on Eurybia has made the informed guess that, although Rough-leaved Aster may flower the first year after germination under optimal conditions, flowering is more likely to occur in the second year (Brouillet pers. comm. 2023). Western Silvery Aster (Symphyotrichum sericeum), another clonal species in the Astereae tribe (but in a different subtribe), has been observed in the same locality for over 20 years (COSEWIC 2021b), and the Montreal Botanical Garden has cultivated White Wood Aster (Eurybia divaricata) for 15 to 20 years (Brouillet pers. comm. 2023). Stems of Large-leaved Aster (Eurybia macrophylla) have grown from the same patch for over 20 years (Blaney pers. comm. 2023). It is presumed that Rough-leaved Aster has a similar lifespan and that ramets are equally long-lived. Generation time (defined as the average age of individuals capable of vegetative and/or sexual reproduction) is estimated at 10 or more years.

The fecundity of Rough-leaved Aster is not known. Although each flowering stem has 5 to 30 floral heads, each with 30 to 70 disc florets (Brouillet 2006), the number of viable seeds produced is unknown. Seed set is low in other rare perennial aster species (COSEWIC 2009, 2021b); Eurybia and other aster genera in the subtribe Astereae are primarily self-incompatible (Gavin-Smyth et al. 2001; Ferrer and Good-Avila 2006). All subpopulations in Canada are small (four of the five subpopulations have 101 shoots or fewer), and it is impossible to know how many different individuals are present without excavating the plants, so the true population size is unknown. Seeds that appear to be viable have been observed on herbarium specimens (Batten pers. obs. 2023), but have not been tested. Germination and seedling establishment have not been observed in the wild in Canada. Longevity in the seed bank is unknown (Brouillet pers. comm. 2023; Semple pers. comm. 2023). The seeds of some Canadian species in the same, albeit large, subtribe as Eurybia are short-lived and persist for only a few years in the seed bank (for example, Chmielewski and Semple 2003; Kemp and Lacroix 2006).

The age at which stems reproduce via a rhizome is unknown. Colonies, which are presumed to be composed of a single genet, are small (several metres in diameter) and rhizome spread does not appear to be limited by habitat. The number of stems per clone is not known.

Rough-leaved Aster is primarily diploid, with some triploids found in the southern part of the species’ U.S. range (2n = 18, 3n = 27) (Semple et al. 2001; Brouillet 2006; Selliah and Brouillet 2008; Semple 2014).

Habitat requirements

In the United States, Rough-leaved Aster habitat is described as consisting of forest edges, open forests and dry rock outcrops in oak woodlands or Ponderosa Pine (Pinus ponderosa) forests, at elevations ranging from 100 m to 1,600 m (Brouillet 2006). These sites are often disturbed by human influence, and severe habitat degradation (that is, invasion by non-native species, erosion and habitat conversion due to development) may be the primary limit to longevity (Semple pers. comm. 2023).

In Canada, known subpopulations of Rough-leaved Aster are found in mixed Douglas-fir (Pseudotsuga menziesii), Garry Oak (Quercus garryana), Arbutus (Arbutus menziesii), and Shore Pine (Pinus contorta var. contorta) forests with partial canopy closure (Table 2). The habitat at the historical occurrence at Englishman River is described as being “on dry rocks” (CAN 506453; RBCM V005005, V043034) and, at the historical occurrence at Wellington, as being “on dry ridge” (RBCM V043035). The Francis/King Regional Park subpopulation is next to a rock outcrop, but the other extant subpopulations are found on level ground or on slight slopes. These sites are moderately moist and with moderately rich soils, occurring at elevations ranging from 60 m to 427 m.

The composition of the vegetation understory at these sites is variable, with most having some shrub cover. The shrub species present vary by site, with the most common being Saskatoon (Amelanchier alnifolia), Bristly Bearberry (Arctostaphylos columbiana), Oceanspray (Holodiscus discolor), Barberry (Mahonia spp.), Falsebox (Paxistima myrsinites), Trailing Blackberry (Rubus ursinus) and Thin-leaved Snowberry (Symphoricarpos albus). The forb cover is also variable and includes a mix of native and non-native species.

All the known extant subpopulations are located next to hiking trails or roads, with plants not observed to extend more than 5 m from these linear features. The species’ preferred habitat is presumed to be on the edges of disturbed areas, where there are higher light levels; however, it is possible that this distribution is related to human-mediated dispersal mechanisms.

Movements, migration, and dispersal

The seeds of Rough-leaved Aster are connected to a quadruple pappus (that is, composed of four whorls) (Semple and Hood 2005; Semple 2014). Dispersal is presumed to be facilitated by wind and updrafts. Most wind-dispersed Asteraceae seeds fall close to the parent plant (within 2 m), but long-distance dispersal of over 100 m has been observed in 0.05% of seeds (Tackenberg et al. 2003; Greene 2005; Cummins et al. 2008). The migration rate of a wind-dispersed Eurybia species typical of open forests in eastern North America was found to be 12 m per year (Singleton et al. 2001). All known extant subpopulations of Rough-leaved Aster in Canada occur next to hiking trails or roads, suggesting that dispersal along these linear features could also be human mediated.

In other Asteraceae species, the pappus, in addition to acting as a mechanism for wind dispersal, protects the ovary and fruit from predation and increases the percentage and speed of seed germination (Pliszko and Kostrakiewicz-Gierałt 2020).

Interspecific interactions

Predators and competitors:

Stems grazed by native Black-tailed Deer (Odocoileus hemionus) and possibly non-native Eastern Cottontail rabbits (Sylvilagus floridanus) have been noted, including during the 2022 field surveys (Roemer pers. comm. 2014 in BC CDC 2014; Maslovat and Batten pers. obs. 2022). The impact on the species’ reproductive success is not known.

Other interactions:

No studies have been done on pollinators of Rough-leaved Aster in Canada. In California, Rough-leaved Aster is a confirmed host of the Northern Checkerspot butterfly (Chlosyne palla) and is also likely used by Hoffmann’s Checkerspot (C. hoffmanni) and the moths Scrobipalpula psilella and Lyonetia prunefoliella (California Native Plant Society 2022). Although some of these pollinator species occur in British Columbia, their range does not overlap with that of the Rough-leaved Aster (eFauna 2023). Other Eurybia species are important to a wide range of pollinators and are commonly recommended for pollinator gardens (for example, Missouri Botanical Garden 2023; North Carolina State Extension 2023; Northeast Pollinator Plants 2023). There have been no studies on seed predation.

Physiological, behavioural, and other adaptations

No studies have been conducted on Rough-leaved Aster physiology or adaptations. The species tolerates the summer drought conditions on southeastern Vancouver Island. It is successfully propagated in the United States for horticultural purposes and has been readily grown in containers from vegetative material collected in the wild in British Columbia (Armstrong 1974; Miskelly pers. comm. 2023; Figure 4).

Limiting factors

Limiting factors are generally not human-induced and include intrinsic characteristics that make the species less likely to respond to conservation efforts. These factors may become threats if they result in population decline. Grazing by native Black-tailed Deer may limit successful reproduction, although its impact is not known. Failure to flower in subpopulations that occur in shady habitat may limit successful reproduction; it is presumed that these subpopulations were established when canopy conditions were more open and that they require some disturbance to maintain sufficient light for flowering. The life history traits of Rough-leaved Aster (self-incompatibility, clonal growth and small, fragmented populations) can magnify the negative impacts of genetic bottlenecks, and reduced genetic diversity and adaptive potential (Gavin-Smyth et al. 2001). It is unknown whether the species is suffering from genetic bottlenecks or genetic drift, or if it produces viable seed in Canada.

Population sizes and trends

Data sources, methodologies, and uncertainties

The population size of Rough-leaved Aster was determined by summing the 2022 counts of flowering and non-flowering shoots in all subpopulations. All known extant subpopulations (that is, excluding historical subpopulations with insufficient locality information) were surveyed by the report writers prior to the drafting of this status report. It is presumed that the historical subpopulations have been extirpated, so these sites are not included in the population size estimates.

Abundance

Rough-leaved Aster is currently known from five extant subpopulations, which correspond to BC CDC element occurrences. These subpopulations contain a total of 330 flowering shoots and 788 non-flowering shoots (Table 1). The number of flowering shoots per subpopulation ranges from 0 to 308 and the number of non-flowering shoots, from 8 to 645.

Given the species’ rhizomatous growth form, it is reasonable to assume that, at each site, flowering and non-flowering shoots are connected underground and are clones of the same individual. Therefore, the number of genetic individuals (genets) is less than the number of flowering shoots. However, in colonial organisms, a mature individual should be defined as the smallest entity that an organism can be divided into (that is, a ramet) and still survive and reproduce (IUCN Standards and Petitions Committee 2024). In total, there are 1,108 shoots of Rough-leaved Aster. Not all severed shoots are likely to survive and reproduce, due to competition for resources and the size of the fragment. Furthermore, many non-flowering shoots are simply a small cluster of leaves. Without data on the viability of individual stem fragments, the number of mature individuals must be considered to be greater than the number of flowering shoots (330) and less than the total number of shoots (1,108), and is estimated to be below 1,000.

Fluctuations and trends

No long-term monitoring or population modelling data are available to determine fluctuations and trends. Rough-leaved Aster appears to be a long-lived species; the population is expected to remain relatively stable over time in the absence of habitat destruction, excessive competition and canopy overgrowth. Previous subpopulation size estimates by botanists surveying the species were made within the last ten years, so long-term trends are not available.

Continuing decline^{Footnote 2} in number of mature individuals:

Unknown due to lack of long-term monitoring.

Evidence for past decline (3 generations or 10 years, whichever is longer) that has either ceased or is continuing:

Unknown due to lack of monitoring. Previous estimates of subpopulation size suggest that subpopulations are stable, but all counts date to the last 10 years or less, which is shorter than three generations. The status of historical subpopulations that lack sufficient locality data and could not be surveyed are unknown. Some of the historical subpopulations may have been destroyed by habitat conversion.

Evidence for projected or suspected future decline (next 3 generations or 10 years, whichever is longer, up to a maximum of 100 years):

Unknown due to the lack of previous long-term population estimates for carrying out trend analysis. Ongoing habitat conversion due to development and impacts from invasive species and fire and fire suppression will likely continue to degrade habitat over the long term.

Long-term trends:

Unknown due to lack of long-term monitoring data for carrying out trend analyses. Habitat destruction on Vancouver Island associated with land conversion is ongoing and it is possible, based on these habitat trends, that subpopulations may be destroyed before they are recorded. The impacts of invasive species and fire and fire suppression will continue to degrade habitat.

Population fluctuations, including extreme fluctuations:

Unknown due to a lack of monitoring. Known subpopulations appear stable over the short term based on previous estimates. The increase in the number of individuals in two subpopulations represents the discovery of new sites in those subpopulations due to the increased survey effort rather than to an actual increase in numbers.

Severe fragmentation

More than 50% of the known population in Canada is found in one subpopulation, Cowichan River. Although this subpopulation has persisted since it was first recorded in 2013, it is unknown if the habitat patches hosting this subpopulation will be able to continue to support a viable population over the long term. The other extant subpopulations are widely separated by distances greater than the species can be expected to disperse; however, there appears to be suitable habitat between these patches that could support Rough-leaved Aster.

Rescue effect

Rough-leaved Aster is abundant and not at risk outside Canada, but the closest extant occurrence is approximately 250 km away, in the state of Washington. Long-distance dispersal events (that is, over 100 m) are possible, but the distance required for natural immigration from outside Canada is extreme. Propagules dispersing from Washington would need to cross the Strait of Juan de Fuca to become established. The habitat conditions in the United States and Canada appear to be similar, and it is presumed that plants from the United States would be able to survive in Canada. However, since Canadian plants have not expanded into what appears to be suitable adjacent habitat, other factors appear to be limiting.

Threats

Historical, long-term, and continuing habitat trends

Rough-leaved Aster is found exclusively in the Coastal Douglas-fir biogeoclimatic zone, where 49% of the land base has been permanently converted by human activities (Hectares BC 2010 in CDFCP 2022) and where forestry activities have altered over 50% of the remaining land (Madrone Environmental Services 2008).

Six historical subpopulations could not be relocated due to a lack of locality data and insufficient funding for surveys (Pike Lake, Englishman River, Wellington, Horne Lake, Mt. Finlayson and Sea’s Farm). It is unknown whether these subpopulations persist, although the habitat has most likely been destroyed by residential and commercial development.

Plants in the Cowichan River subpopulation grow along the roadside on land owned by First Nations and multiple private landowners, while the Francis/King Regional Park subpopulation is located on private land in a highway right-of-way. Landowners may inadvertently damage the habitat by activities such as lawn mowing, ditch clearing and the addition of gravel to road surfaces; however, the immediacy of this threat is unknown and possibly outside the time frame of the threats assessment. Future threats associated with development in known subpopulations in regional parks are presumed to be minimal.

Current and projected future threats

Rough-leaved Aster is vulnerable to the cumulative effects of various threats. The nature, scope and severity of these threats are described in Appendix A, following the IUCN-CMP (International Union for the Conservation of Nature – Conservation Measures Partnership) unified threats classification system (see Salafsky et al. 2008 for definitions and Master et al. 2012 for guidelines). The threat assessment process involves assessing impacts for each of the 11 main categories of threats and their subcategories, based on the scope (proportion of population exposed to the threat over the next 10‑year period), severity (predicted population decline within the scope during the next 10 years or 3 generations, whichever is longer, up to ~100 years) and timing of each threat. The overall threat impact is calculated by taking into account the separate impacts of all threat categories and can be adjusted by the species experts participating in the threats evaluation.

The overall threat impact to Rough-leaved Aster is considered to be Medium – Low. These values must be interpreted with caution, as they may be based on subjective information such as expert opinion, although efforts have been made to corroborate the scores with available studies and quantitative data.

Natural system modifications: other ecosystem modifications (IUCN # 7.3; medium – low)

The invasive shrub Scotch Broom (Cytisus scoparius) is present in Rough-leaved Aster habitat in all but one subpopulation, affecting 99% of the population. Scotch Broom degrades habitat conditions by casting shade and changing soil chemistry, which can create more favourable conditions for other invasive species (Slesak et al. 2016). Scotch Broom also changes the habitat structure by increasing the density of the shrub layer, which may affect pollinators’ access to Rough-leaved Aster. The invasive shrub Spurge-laurel (Daphne laureola) was also present at one site.

Non-native invasive grasses are present at most sites. Invasive grass species include Creeping Bentgrass (Agrostis stolonifera), Sweet Vernalgrass (Anthoxanthum odoratum), Barren Brome (Bromus sterilis), Orchard Grass (Dactylis glomerata), Tall Ryegrass (Lolium arundinaceum) and Kentucky Bluegrass (Poa pratensis). These grasses likely compete with Rough-leaved Aster for moisture and light and may occupy the protected sites that the latter requires for germination.

The presence of non-native forbs is variable and includes Oxeye Daisy (Leucanthemum vulgare), Common Nipplewort (Lapsana communis), Common St. John’s-wort (Hypericum perforatum), Hairy Cat’s-ear (Hypochaeris radicata), English Plantain (Plantago lanceolata) and Curled Dock (Rumex crispus); these species may compete for resources with Rough-leaved Aster. Poison-hemlock (Conium maculatum) has been recorded within 200 m of the Thetis Lake Regional Park subpopulation (Ministry of Forests 2023), but poses a low risk owing to the distance involved (Brown pers. comm. 2023).

Natural system modifications: fire and fire suppression (IUCN # 7.1 low)

The role of fire in the successful reproduction of Rough-leaved Aster is not known; fire suppression has resulted in the encroachment of forest and other vegetation on formerly open habitat, causing decreased light levels and possibly resulting in limited flowering. The closely related Western Showy Aster (Eurybia conspicua), a perennial aster found in Douglas-fir forests, is top-killed by fire but resprouts from its surviving rhizomes, resulting in extensive flowering 1 to 2 years following a burn. The lack of competition after a burn also allows regeneration from wind-dispersed and soil-banked seed (FEIS 2023). However, ongoing fire suppression in coastal Douglas-fir ecosystems has led to higher fuel loads, which could result in high-intensity catastrophic fires that could kill Rough-leaved Aster crowns.

Although human-caused fires are possible along roadsides and trails, such fires are quickly suppressed in populated areas. The impact of fires with higher fuel loads and fire suppression on Rough-leaved Aster dispersal, persistence and fecundity is unknown.

Transportation and service corridors: roads and railroads (IUCN #4.1 unknown)

The two subpopulations with the largest number of flowering stems (Francis/King Regional Park and Cowichan River) are adjacent to paved roads that are maintained by the B.C. Ministry of Transportation and Infrastructure (MOTI). Maintenance includes mowing road rights-of-way, and cut stems were observed in the portion of the Francis/King Regional Park subpopulation that occurs on a nearby public road outside the park. Depending on the timing, maintenance activities may limit sexual reproduction in these subpopulations. However, mowing may also benefit the plants by keeping roadsides open, limiting shrub competition and maintaining the high light conditions required for flowering. More intensive road work could severely impact plants, but no plans to widen roads are known at this time.

The role of disturbance in maintaining light conditions for successful reproduction is unclear. The lack of flowering in three of the five subpopulations appears to be associated with shade. It is unclear if these subpopulations became established when conditions were more open.

Pollution: agricultural and forestry effluents (IUCN #9.3 unknown)

Fire retardants used for fire suppression may increase nitrogen levels, which may favour non-native species, as well as covering the plants for short periods. Asbestos from brake pads and tire wear pollutes roadsides. Brining of roads with salt does occur in the winter months, but high levels of precipitation may limit the threat. The impact of these pollutants either individually or in combination on Rough-leaved Aster is not known.

Invasive and other problematic species, genes and diseases: invasive non-native/alien species/diseases (IUCN #8.1 unknown)

Non-native Eastern Cottontails are pervasive on eastern Vancouver Island. Although browsing on plants has been reported, there is no direct evidence that the rabbits are involved; this could potentially limit reproduction (Roemer pers. comm. 2014 in BC CDC 2014; Maslovat and Batten pers. obs. 2022).

Invasive and other problematic species, genes and genes: problematic native species/diseases (IUCN #8.2 unknown)

Overgrazing by Black-tailed Deer (Odocoileus hemionus) has been observed and may limit successful reproduction (Roemer pers. comm. 2014 in BC CDC 2014; Maslovat and Batten pers. obs. 2022). This deer, although native, is found in high abundance in some localized areas, including extreme southeastern Vancouver Island.

Geological events: earthquakes/tsunamis (IUCN #10.2 unknown)

Although Vancouver Island is in an earthquake zone, there is no indication as to when a big earthquake would happen and what its impact would be on this plant.

Climate change and severe weather: droughts (IUCN #11.2 unknown)

Climate change is predicted to bring less summer rain and more days over 30 °C to the region, which will increase drought conditions (Province of British Columbia 2023). Rough-leaved Aster is tolerant of the current summer drought conditions in southeastern Vancouver Island and is capable of surviving farther south in California where more extreme drought conditions occur; however, the impact of the increased frequency of drought associated with climate change is unknown.

Climate change and severe weather: temperature extremes (IUCN # 11.3 unknown)

Increased summer temperatures, including more days over 30 °C, is predicted for southwestern British Columbia (Province of British Columbia 2023). Although the plants survived the 2021 western heat dome, the impact of future temperature extremes associated with climate change is unknown.

Climate change and severe weather: storms and flooding (IUCN #11.4 unknown)

Extreme storm events and more intense autumn rain events are predicted to occur with future climate change (Province of British Columbia 2023). Plants have survived recent severe atmospheric river events; however, the future impact from storms and flooding is unknown.

Number of threat locations

There are five subpopulations as defined by the BC CDC’s element occurrence records. Using the COSEWIC definition of location (that is, a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals present), there are six locations because the site of the Cowichan River subpopulation has multiple landowners (threats categorized by location are included in Table 3).

Protection, status, and recovery activities

Legal protection and status

COSEWIC assessed Rough-leaved Aster as Threatened in May 2024 and it is not listed under the Species at Risk Act.

Non-legal status and ranks

Rough-leaved Aster is provincially assessed as Imperilled (S2) and is on the province’s Red List (BC CDC 2022; NatureServe 2022). In 1988, NatureServe ranked Rough-leaved Aster as Imperilled (N2) in Canada and Apparently Secure/Secure (G4G5) globally (B.C. Conservation Data Centre 2022; NatureServe 2022). In the United States, the species is Unranked (NNR) nationally, as well as at the state level (SNR) in California, Oregon and Washington (NatureServe 2022). It is not listed under the Convention on International Trade in Endangered Species (CITES 2022) and has not been assessed by the International Union for Conservation of Nature (IUCN) (IUCN 2022).

Land tenure and ownership

The ownership of Rough-leaved Aster subpopulations is listed in Table 3. Among the five extant subpopulations, the three smallest ones are in regional parks and are therefore protected from development (approximately 7% of the total population based on the number of shoots). The other two subpopulations are found in and next to MOTI rights-of-way. Of the two subpopulations found in rights-of-way, the largest is on First Nations reserve land and nearby private land (83% of the total population based on the total number of shoots) and the second largest is on private land (10% of the total population based on the total number of shoots).

Information sources

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Collections examined

The following collections were queried and/or examined for the preparation of this report:

• National Herbarium of Canada, Canadian Museum of Nature (CAN): 102254 (Macoun 1887); 506453 (Carter 1916)
• Consortium of Pacific Northwest Herbaria Specimen Database (accessed online): Specimens listed under herbarium of origin
• National Collection of Vascular Plants (previously Department of Agriculture, Ottawa) (DAO): 102253 (Macoun 1893); 543636 (Armstrong 1974); 543637 (Armstrong 1974); 543639 (Armstrong 1974); 651773 (Armstrong and Armstrong 1973)
• Royal British Columbia Museum (V): V005005 (Carter 1916), V043034 (Carter 1916), V043035 (Carter 1916); V101755 (Melburn 1969); V140296 (Armstrong and Armstrong 1974); V140297 (Armstrong and Armstrong 1975); V209061 (Miskelly and Allen 2011); V217816 (Roemer 2013); V217815 (Roemer 2013); V217840 (Roemer 2014)
• University of British Columbia Herbarium (UBC): V253015 (Lomer, Batten and Roemer 2018)

Authorities contacted

• Asencio, S. Collections Manager, National Collection of Vascular Plants, Agriculture and Agri-Food Canada. Ottawa, Ontario
• Batten, R. Botanist, B.C. Conservation Data Centre and Beacon Botanical Research. Victoria, British Columbia
• Blaney, S. Executive Director and Senior Scientist, Atlantic Canada Conservation Data Centre
• Brouillet, L. Professor (retired), University of Montreal. Montreal, Quebec
• Brown, B. Invasive Plant Specialist, Provincial Early Detection Rapid Response Coordinator, Ministry of Forests. Nanaimo, British Columbia
• De Forest, L. Species Conservation Specialist, Parks Canada Agency. Halifax, Nova Scotia
• Doubt, J. Curator, Botany, Canadian Museum of Nature. Ottawa, Ontario
• Filion, A. Scientific and GIS Project Officer, COSEWIC Science Support, Canadian Wildlife Service, Environment and Climate Change Canada. Gatineau, Quebec
• Govindarajulu, P. Unit Head, Species Conservation Unit, Conservation Science Section, Ecosystems Branch, Ministry of Environment and Climate Change Strategy. Victoria, British Columbia
• Kroeker, N. Species Conservation Implementation Manager, Parks Canada Agency, Western Canada Region. Victoria, British Columbia
• Lake, R. Head, Regulatory Affairs, Canadian Wildlife Service, Environment and Climate Change Canada. Nanaimo, British Columbia
• Miskelly, K. Owner, Satinflower Nursery. Metchosin, British Columbia
• Mollin, J. Permitting Officer, Capital Regional District Parks. Colwood, British Columbia
• Robinson, J. Senior Conservation Biologist, Capital Regional District Parks. Colwood, British Columbia
• Roemer, H. Botanist. Victoria, British Columbia
• Sadler, K. Head, Species at Risk Recovery, Canadian Wildlife Service, Environment and Climate Change Canada. Nanaimo, British Columbia
• Schnobb, S. Program Support Specialist, COSEWIC Secretariat. Gatineau, Quebec
• Semple, J.C. Professor Emeritus and Adjunct Professor, University of Waterloo. Waterloo, Ontario
• Shepherd, P. Species Conservation and Management Ecosystem Scientist III, Parks Canada Agency. Sidney, British Columbia
• Wu, J. Scientific Project Officer, Environment and Climate Change Canada. Gatineau, Quebec

Acknowledgements

Funding for the preparation of this report was provided by Environment and Climate Change Canada. The writers would like to thank Jill Robinson and Jeanette Mollin for facilitating the permits to access Capital Regional District Regional Parks for surveys. Alain Filion prepared the distribution map and calculated the EOO and IAO for this report. John Semple and Luc Brouillet provided important information about the biology of the species. Kristen Miskelly provided information about propagation. Many thanks to Del Meidinger for his assistance in supporting this document through to completion. The authorities listed above provided valuable data and/or advice.

Biographical summary of report writer(s)

Carrina Maslovat works as a botanist specializing in plant communities at risk, primarily Garry Oak ecosystems. Her work includes conducting inventories of rare plants in regional, municipal, federal and provincial parks; finding new subpopulations of species at risk and monitoring the abundance and vitality of rare plant populations over time. She has drafted a number of reports as part of her work, including management plans for nature reserves, best management practices for minimizing impacts on species at risk, four COSEWIC status reports, four status report updates, and several recovery planning documents. She has also designed and implemented ecological restoration projects to provide habitat for species at risk.

Ryan Batten is a botanist and plant ecologist with 15 years of experience, specializing in rare plants, wetlands and biodiversity inventories. He brings a broad floristic knowledge from conducting field work in British Columbia, Alberta, Saskatchewan, Ontario and Nunavut. He is an active member of the B.C. Flora Update Committee and has been affiliated with the Royal BC Museum Herbarium for the last decade. In 2019, he prepared the status ranks for all of B.C.’s vascular plants for the federal government’s General Status of Wild Species in Canada program. Ryan works frequently with the B.C. Conservation Data Centre, where he spends the majority of his time drafting conservation status reports, mapping the ranges of rare species and providing training on NatureServe’s status assessment methodology. His current research interests include geospatial floristics, human-mediated dispersal and traits of rarity.

Appendix A. Threats calculator

Threats assessment worksheet

Species or ecosystem scientific name

Rough-leaved Aster - Eurybia radulina

Date

2023-03-28

Assessor(s)

Del Meidinger and Bruce Bennett (SSC Co-chairs); Anna Hargreaves, Brenda Costanzo and David Mazzerole (SSC members); Ryan Batten and Carrina Maslovat (report writers); Alyssa Pogson (COSEWIC Secretariat)

Assigned overall threat impact

CD = Medium - Low

Overall threat comments

Generation time estimated at 5 to 10 years; three generations, at 15 to 30 years. Cowichan River site has 80 to 90% of population; Francis-King Park (regional park), 5 to 10%.