PHYTOGEOGRAPHY OF THE NATIVE VASCULAR PLANTS OF BRITISH COLUMBIA
Arctic willow (Salix arctica), photo by Virginia Skilton. This is a circumpolar species.
George W. Douglas, Del Meidinger
and Jim Pojar
Text reprinted from the Illustrated Flora of British Columbia, Volume 8,
The native vascular plant flora of British Columbia has a complex and varied history, especially with respect to glaciation. It consists of a total of 2316 taxa within a number of floristic elements* and sub-elements. These elements range from widespread cosmopolitan species to coastal endemics. The synopsis presented here includes the major elements in the flora, some of their sub-elements, the number of native BC taxa within these and examples of representative taxa.
[*Editor's note: Species may be grouped with others
that share similar distribution patterns to form what can be termed elements.]
This is the widest ranging of our phytogeographic
elements and contains those taxa that have a worldwide distribution
in both hemispheres. Only a small number of our taxa (27)
belong to this element. Some of these include Isolepis
cernua, Hutchinsia procumbens, Juncus bufonius, Stuckenia
pectinata, Triglochin maritima and Zostera
Plants in this element occur in both the Northern
and Southern Hemispheres. This type of disjunction is not
readily explained, although Raven (1963) has suggested that most
of these plants probably reached their disjunct areas by long-distance
dispersal relatively recently. A total of 45 BC taxa belong
to this element. Typical examples include Lilaea scilloides,
Osmorhiza berteroi, Pectocarya penicillata, Sanicula graveolens,
Schoenoplectus americanus and Trifolium
This group of widely distributed plants contains 16% (365
in total) of our flora. Although this element could be further subdivided into
circumboreal, circumarctic and circumalpine elements (sensu Schofield 1969),
we have not attempted that here. Representative species include Carex
pauciflora, Hierochloe hirta ssp. arctica, Listera cordata, Potentilla nana,
Salix arctica, Saxifraga hieracifolia var. hieracifolia and Senecio conestus (syn. Tephroseris palustris).
This element includes species that occur on both sides
of the Bering Sea, extending westward into Asia and eastward into North America. The
role of the Bering Land Bridge in the distribution of northern plants has been
the subject of numerous floristic papers (e.g. Hulten 1937, Porsild 1955) We
have also included within this element a number of North Pacific Basin species
that probably did not extend their ranges via the Bering Land Bridge, but rather
by the Aleutian Island Chain. Many of these North Pacific Basin species
(i.e. Carex macrochaeta, Hymenophyllum wrightii and Platanthera
chorisiana) are readily identified but many others, due to more continental
distribution, are not. A total of 179 taxa (8% of the flora) belong to this
amphiberingian element. Examples of these include Arnica lessingii, Antennaria
monocephala, Cardamine oligosperma, Carex membranacea, Rumex arcticus, Senecio
fuscatus (syn. Tephroseris lindstroemii) and Spiraea stevenii.
North American Maritime Species
Taxa belonging to this element occur along both the Pacific and Atlantic Coasts in North America and sometimes along the Arctic Coast. Some of the nine plants in this element include Salicornia virginica (syn.
Salicornia depressa, Sarcocornia pacifica), Senecio pseudoarnica, Spergularia canadensis var. canadensis and Puccinellia pumila.
North American Radiants
Plants in this element range across large parts of
North America. For this treatment,we have recognized this as a broad
group, without sub-elements (i.e. American Boreal, southern North America,
etc.). Twenty-six percent of the flora (a total of 612 taxa) occurs in this
species include Carex peckii, Platanthera orbiculata, Primula mistassinica,
Senecio pauperculus, Solidago multiradiata, Sporobolus compositus and Vaccinium
This group contains species that occur primarily in the
western Cordillera but which may have a small part of their range extending
into more eastern or northern regions. These taxa comprise about 35% of the
flora (a total of 816 taxa). Typical examples of Cordilleran species
are Arnica latifolia, Aster engelmannii (syn. Eucephalus engelmannii), Draba albertina, Lupinus wyethii,
Phacelia sericea, Rubus pedatus, Saxifraga mertensiana and Senecio
Packera streptanthifolia, Packera subnuda).
Alaska-Yukon-Northwestern British Columbia Endemics
This group consists of species restricted to Alaska, Yukon
and immediately adjacent northwestern British Columbia and occasionally the
Northwest Territories. Most of these endemics probably originated in
a large glacial refugium in northern Alaska and the Yukon. Some, however, must
have persisted on unglaciated munataks or other areas farther south (Douglas
et al. 1981). A small number of these (25 taxa) have reached the mountains
of extreme northwestern British Columbia. Representative taxa include Astragalus
nutzotinensis, Douglasia gormanii, Montia bostockii, Oxytropis huddelsonii,
O. scammaniana, Salix setchelliana and Senecio ogotorukensis.
Pacific Coast Endemics
This element consists of mesophytic Pacific Coast species
that have their ranges extending over large parts of the Pacific Coast between
Alaska and Mexico. The 238 taxa (10% of the flora) in this Pacific Coast
element may be further subdivided into three sub-elements:
Entire Pacific Coast Endemics
These taxa have ranges that extend from Alaska to Oregon, California or Mexico. This sub-element consists of 56 taxa and includes species such as Cardamine angulata, Carex obnupta, Malus fusca, Oenanthe sarmentosa, Oxalis oregana, Poa laxiflora, Ribes bracteosum and Sedum oreganum.
North Pacific Coast Endemics
This sub-element includes 30 plants that have ranges between Vancouver Island and Alaska. Ten of these plants have their main distribution in the Queen Charlotte Islands (Calder and Taylor 1968). Representative species include Atriplex alaskensis, Castilleja unalaschcensis, Gentiana douglasiana, Lloydia serotina var. flava, Lupinus nootkatensis, Polystichum setigerum, Salix reticulata ssp. glabellicarpa and Senecio
Packera subnuda var. moresbiensis).
South Pacific Coast Endemics
The South Pacific Coast sub-element contains taxa
with ranges that extend from Vancouver Island (usually the southern part
of the Island) southward varying distances to Mexico. In British
Columbia, this sub-element consists of about seven percent of the flora
(152 taxa) and is represented by taxa such as Artemisia suksdorfii,
Aster chilensis (Symphyotrichum ascendens), Lomatium utriculatum, Sanicula arctopoides, S. bipinnatiida,
Senecio macounii (Packera macounii) and Trifolium depauperatum var. depauperatum. A few
members of this sub-element (Bidens amplissima, Limnanthese macounii and Aster
paucicapitatus) do not have ranges extending beyond British Columbia
or northwestern Washington.
[Editor's note: Since the
writing of this text, Bidens amplissima has since been reported
from Washington and is likely present in Oregon.]
British Columbia Endemics
Another group of endemics of interest are the 46 taxa that occur in British Columbia and immediately adjacent regions (Douglas 1996). Nine of these taxa are restricted solely to British Columbia and belong to two groups: a Queen Charlotte Island/northern Vancouver Island/adjacent mainland group (7 taxa) and a southern Vancouver Island/adjacent islands and mainland group (2 taxa). A total of 19 taxa are part of the Pacific Coast endemics described above, while the remaining 27 occur in the Cordilleran region of British Columbia and immediately adjacent states and provinces.
For references used in this article, please visit the General Referenes for the Illustrated Flora of British Columbia.