Phyllodoce empetriformis (Sm) D. Don. (G4-S1S2): Pink mountain-heather is a low, matted, evergreen shrub of mesic, acidic soils in montane and alpine habitats. The leaves are needlelike and shiny; the flowers are rose-pink nodding, and open (Fig. 41) rather than constricted at the mouth like P. caerulea and P. glanduliflora (Szczawinski 1962). Phyllodoce gladuliflora was found co-occurring with P. empetriformis in KLGO. In British Columbia, P. empetriformis is known to hybridize with the more widespread, yellow-flowered, P. glanduliflora, producing an intermediate form of white to pale rose corollas and other intermediate forms (Meidinger 1999). The hybrid can be quite common and has been described as P. x intermedia (Hook.) Camp.
The range of this species is Cordilleran, occurring occasionally from the mountains of California and Wyoming northwest through Washington and British Columbia. The species enters Alaska only at the head of Lynn Canal. While the range of pink mountain-heather is not particularly narrow, populations are restricted to a specific and uncommon high-elevation habitat type. The Washington National Heritage Program identifies two community types composed of P. empetriformis as being “high-quality or rare habitat.â€ÂÂÂ
Four collections of P. empetriforims are reliably known from Alaska and these are clustered in mountains along the Klehini River near Haines. Duffy and McWorter made collections in 2000 at Flower Mountain and Four Winds Mountain (ALA 2003). Carolyn Parker (2001) made collections from a population on a granitic outcrop on Takhin Ridge. One collection is from a nunatak on the Juneau Icefield, the east side of Taku Towers. Beschel collected the specimen in 1965 and stated that it was the only one seen on the Juneau Icefield (AKNHP database 2003). There are a few historic collections (e.g., Bolton 1898, cited in Hultén 1941-1950), likely on the Canadian side, from the White Pass - Summit Lake area.
In a broader, regional context, P. empetriformis is relatively common in the Cassiar Mountains and Yukon Plateau in the north and the Columbia and Cascade mountains of southern British Columbia, but is absent from the west side of the Coast Mountains, except from Vancouver Island south into Washington (Fig. 42). This distribution suggests that the species was primarily found to the south during glacial maxima and has migrated north and up in elevation, tracking appropriate climate and habitat zones (as many species are known to have done, e.g., Vaccinium: Camp 1942, Pinus contorta: MacDonald and Cwynar 1985, and see Pielou 1992 for additional discussion). A few populations of pink mountain-heather are now stranded on high elevation mountain “islands†in New Mexico and Idaho.
Alternatively, the presence of P. empetriformis on a nunatak in southeast Alaska indicates that it is possible the species may have persisted in situ and later spread to current locations. This seems unlikely since only a single individual has been observed on southeast Alaskan nunataks and may be the result of a chance dispersal event (e.g., mountain goats are known to travel long distances across ice fields often stopping to feed and rest at nunataks – plant propagules caught in their wool could thus be deposited at such sites).
The pattern of species expanding their ranges through interior B.C. and then only spilling across the Coast Range in Lynn Canal, rather than migrating along the coastal corridor (with apparently appropriate habitats) from Vancouver Island is curious. However, long-distance dispersal is likely limited for this species (fruits are dry, dehiscent capsules and seeds are not adapted for wind dispersal) and the numerous fjords of the Alexander Archipelago may be a significant barrier to migration. Interior British Columbia is much less geographically fractured and may have offered an unimpeded advance at the heels of retreating glaciers.
Regardless, of the mechanism behind the occurrence of P. empetriformis in the White Pass area, it highlights the importance of this area as a corridor for species interchange.