Stoloniferous pussytoes (Antennaria flagellaris) COSEWIC assessment and status report: chapter 4

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Distribution

Global range

Antennaria flagellaris ranges from southwestern British Columbia, south in the western United States to Idaho, Wyoming, Nevada and California (Cronquist 1994; Figure 2). The nearest known occurrence to the BC population is in central Washington, on the Naches River (Hitchcock 1964), about 190 km to the south. Dispersal is by wind. Considering the distance and the limited habitat available, it is unlikely that United States populations will provide emigrants that can contribute to a rescue effect.

Figure 2. Distribution of Antennaria flagellaris in North America.

Canadian range

In Canada, A. flagellaris is known only from a 3.2 length of Highway 3 in the Similkameen River valley, over about 4.8 km², southwest of Princeton in southwestern British Columbia (Douglas 1998; Douglas et al. 2002a, b; Figure 3).

Antennaria flagellaris is just one of a number of species recently discovered (since the1980s) along the British Columbia border from the Princeton area to the Roosville area. Some of these other species include: Carex vallicola, Collomia tenellus, Floerkea proserpinacoides, Hedeoma hispida, Lipocarpha micrantha, Orobanche ludoviciana, Orthocarpus barbatus, Phacelia ramosissima, Psilocarphus brevissimus, Silene spaldingii  and Trichostema oblongum (Douglas et al.1998a, b). Most of these species have at least one thing in common; the areas in which they were found were never subjected to botanical collecting. Examination of collection localities in all major herbaria in Canada reveal that none of the many active field botanists working along the border ever collected in the immediate vicinity of the recently collected plants.

This species was discovered in British Columbia in 1996 by F. Lomer. It grows in a natural ephemeral habitat type absent of non-native species in an undeveloped area, so it is unlikely that it was introduced to this site. Furthermore, the region has been generally under-collected so it was likely over-looked. Only one of the other 10 rare plant species that occur in the Princeton area was collected (on one other occasion) prior to 1996. The Princeton area may have been passed over by numerous botanists who were en route from the coast to collecting destinations in the biologically rich Okanagan Valley further east. Another argument that favors this species as a native element is the existence of numerous taxa whose distribution follows a similar pattern in the Pacific Northwest with the northern limit of the species’ range in British Columbia. The shrub steppe and open forests of southern British Columbia are part of a much larger ecological unit that extends south to Washington, Oregon and other intermountain states. In addition, it is likely a native population since it is comprised of several subpopulations, and it would have taken some time to disperse as it has over this area.

Finally, in the Species at Risk Act (Section 2.2), it states that for the purposes of a wildlife species in subsection 1, " a species, subspecies or biologically distinct population is, in the absence of evidence to the contrary, presumed to have been present in Canada for at least 50 years" (Government of Canada 2003). Therefore, since there is no support for the argument that it is a non-native species, it should be assumed native.

Figure 3.  Distribution of Antennaria flagellarisin British Columbia (numbers refer to populations in Table 2).

Frank Lomer was the first collector to intensively investigate this area, especially the areas within the Roany soil series (Figure 4). He has searched for new sites for this species ever since he found it in 1996 (Lomer, pers. com., 2003). He regularly collects throughout the interior of British Columbia in unique or interesting habitats with hopes of new discoveries and keeps an eye out for several rare species including Antennaria flagellaris. He has found no other locations during this time. In both 2002 and 2003, he was contracted to do specific searches for new sites for the rare species known in the Princeton area. He surveyed the east side of the Similkameen River opposite the known sites without success.

Figure 4.  Extent of the Roany soil series in British Columbia(four yellow areas, or pale areas in b/w copies). The three Antennaria flagellaris sites are indicated by the small open white circles between Stevenson Lake and Tracey Lake.

George Douglas also searched the Princeton area in the years 1996, 1999, 2002 and 2003. His early searches (1996, 1999) were not in the areas where A. flagellaris occurs but did encompass the areas of the Roany soil series north of Princeton. All A. flagellaris populations occur within the southwestern roany soils polygon (Figure 4). It is estimated that at least 70% of the potential habitat has been surveyed.