Showy phlox (Phlox speciosa): COSEWIC assessment and status report: chapter 4

Distribution

Global range

Globally, Phlox speciosa ssp. occidentalisoccurs only in western North America (Figure 2). The range in Figure 2 is interpreted from distributional information provided in two floras (Hitchcock et al. 1959, Hickman 1993) and from states of occurrences reported in NatureServe (2004). The species extends from southern British Columbia to northern Oregon and eastward to Idaho and western Montana. From southern Oregon, the species extends into the Sierra Nevada of California and Nevada and the Klamanth and Northern Coast ranges of California.

NatureServe has ranked the global status of Phlox speciosa ssp. occidentalis as G5TNR, meaning “Secure” (common, widespread, and abundant) at the species level, but “not ranked” at the subspecies level (NatureServe 2004).

Figure 2.  The distribution of Phlox speciosa in North America

 

Figure 2.  The distribution of Phlox speciosa in North America.

Canadian range

The Canadian range of Phlox speciosa is illustrated in Figure 3. The taxon has a restricted range, and is known only from the southern interior of British Columbia (Scoggan 1979). All historical, unconfirmed, and confirmed locations for this species occur in the Okanagan Valley.

The nearest population in Washington state may be along the Sanpoil R., about 95 km north of Wilbur and about 128 km south of the main range of the species in British Columbia (Washington State population data courtesy Dr. David Giblin, University of Washington Herbarium).

Figure 3.  Present extent of occurrence of Phlox speciosa in British Columbia

 

Figure 3.  Present extent of occurrence of Phlox speciosa in British Columbia(range of species is represented by the shaded polygon; major lakes are shown as grey areas).

Historically, the taxon is known to occur in the Okanagan Valley from Summerland, at the northern extremity of the species range, south to Skaha Lake (formerly Dog Lake), and southwest to the Twin Lakes (Table 1). The historic Summerland (from 1919) and SkahaLake(from 1927) populations could not be relocated during the June 2003 field survey conducted by Ksenia Barton and Jan Teversham. A brief field survey was conducted in those areas in apparently suitable habitats, but there was no detailed location information available for the Summerland and Skaha Lake sites, and it is possible that the survey failed to find extant populations in those areas. The lack of recent collections/observations at those sites may, however, be an indication that those populations have been extirpated.

Table 1.  Status of Phlox speciosa populations inBritish Columbia.
Populations Number of Sub-populations First Observed Last Observed Population Status
Summerland ? 19191 19191 historical – may be extirpated
Skaha Lake
(=Dog Lake),
west of Skaha Lake (=Dog Lake)
?
?

19271

?

19271

­–

historical – may be extirpated

historical – may be extirpated
Osoyoos ? ? ­– recent unconfirmed – possibly misidentified
Twin Lakes 6 19401 20032 confirmed
Yellow Lake East 2 ­19641? 20032 may form a single population with Yellow Lake South and West; 1964 observation not specific about location
Yellow Lake South 2 19971 ­– may form a single population with Yellow Lake East and West
Yellow Lake West 1 ­19641? 20032 may form a single population with Yellow Lake East and South; 1964 observation not specific about location
White Lake 1 20023 20032 confirmed
Ford Lake 2 20032 2003 newly discovered
McKay Creek 1 20032 2003 newly discovered
Park Rill 3 20032 ­2003 newly discovered
Yellowlake Creek 2 20032 ­2003 newly discovered

1BC CDC 2002

2Field survey conducted by Ksenia Barton and Jan Teversham (June 2003)

3Krannitz, pers. comm., 2002

A recent unconfirmed observation of Phlox speciosa was made near Osoyoos. The Osoyoos observation may be a case of misidentification as the observer noted the plants flowering in February and March, while Phlox speciosa flowered in May and June 2003 in all confirmed locations.

Extant and newly discovered populations are concentrated in a cluster around Yellow Lake and Twin Lakes, between the towns of Keremeos and Penticton. Phlox speciosa has been known to occur in the Twin Lakes area since 1940. Of the nine extant populations, four are newly discovered populations and occur within the historical extent of occurrence. It is not known whether the newly discovered populations are recently established, or whether collectors have overlooked them in the past. Most of the populations have more than one sub-population.

The known extent of occurrence is approximately 57 km2. The known area of occupancy is estimated to be within the range of 0.9-1.4 km2. The trends in extent of occurrence and area of occupancy are unknown.

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