18. Biodiversity of Canadian Forests
355
reported a relatively high level of population differentiation within a
small geographic area of coastal Douglas fir in British Columbia. This
they interpreted to be the result of large elevational gradients for Douglas
fir habitats in the sampled region.
Typically, vertebrates have lower levels of genetic diversity than invertebrates, which in turn are less heterozygous than plants (Nevo, 1987).
Because animals are more mobile than plants, differentiation tends to be
detectable only over much larger areas than for plants (Liu & Godt,
1983). Paradoxically, barriers to vertebrate migration tend to be more
significant than for plants that rely on wind for pollination and/or seed
dispersal. Consequently, genetic differentiation in vertebrates is more
commonly recognized at the subspecies levels (see below for further
discussion on west coast fauna).
Species Diversity
There is generally a gradient in tree species diversity from north to south,
with exceptional areas of diversity in southern Ontario, and southern and
western British Columbia (Hosie, 1979). In the enormous boreal forest
region in Canada, only 38 species of tree are found, compared with 36
species in the much more restricted Coastal forest region of British
Columbia and 79 species in the Deciduous forest region of southern
Ontario.
Microorganisms and invertebrates have received little attention from
taxonomists and ecologists despite their species diversity and their major
roles in ecosystem functioning. There have been few studies on these
groups of organisms in Canada's west coast forests. A current study of
canopy arthropods in old-growth, second growth, and clear-cut sites in
the Carmanah Valley of Vancouver Island represents the first of its kind
in temperate rain forests (Winchester, 1993). Analyses of the distribution
of phytophagous and predator/parasitoid arthropods indicate significant
differences among individual trees for both groups in terms of species
densities, as well as among the different sites. The phytophagous arthropods were also affected by seasonal changes. Although there were
no vertical distribution differences for these species, there were highly
significant differences for mites. In particular, the canopy soil litter
associated with moss mats that develop in the old-growth canopy are
dominated by Collembola and Acari, with significant differences at the
generic level, compared with forest floor communities. Due to the absence
of such moss mats in second growth forests , these canopy communities
are obviously not present.
Nonvascular plants have also been relatively little studied in comparison
with vascular plants. About half of the 1013 species of lichens and associated fungi of British Columbia have been reported from five or fewer
sites (Goward, 1991). Although many of these species may indeed be
355
reported a relatively high level of population differentiation within a
small geographic area of coastal Douglas fir in British Columbia. This
they interpreted to be the result of large elevational gradients for Douglas
fir habitats in the sampled region.
Typically, vertebrates have lower levels of genetic diversity than invertebrates, which in turn are less heterozygous than plants (Nevo, 1987).
Because animals are more mobile than plants, differentiation tends to be
detectable only over much larger areas than for plants (Liu & Godt,
1983). Paradoxically, barriers to vertebrate migration tend to be more
significant than for plants that rely on wind for pollination and/or seed
dispersal. Consequently, genetic differentiation in vertebrates is more
commonly recognized at the subspecies levels (see below for further
discussion on west coast fauna).
Species Diversity
There is generally a gradient in tree species diversity from north to south,
with exceptional areas of diversity in southern Ontario, and southern and
western British Columbia (Hosie, 1979). In the enormous boreal forest
region in Canada, only 38 species of tree are found, compared with 36
species in the much more restricted Coastal forest region of British
Columbia and 79 species in the Deciduous forest region of southern
Ontario.
Microorganisms and invertebrates have received little attention from
taxonomists and ecologists despite their species diversity and their major
roles in ecosystem functioning. There have been few studies on these
groups of organisms in Canada's west coast forests. A current study of
canopy arthropods in old-growth, second growth, and clear-cut sites in
the Carmanah Valley of Vancouver Island represents the first of its kind
in temperate rain forests (Winchester, 1993). Analyses of the distribution
of phytophagous and predator/parasitoid arthropods indicate significant
differences among individual trees for both groups in terms of species
densities, as well as among the different sites. The phytophagous arthropods were also affected by seasonal changes. Although there were
no vertical distribution differences for these species, there were highly
significant differences for mites. In particular, the canopy soil litter
associated with moss mats that develop in the old-growth canopy are
dominated by Collembola and Acari, with significant differences at the
generic level, compared with forest floor communities. Due to the absence
of such moss mats in second growth forests , these canopy communities
are obviously not present.
Nonvascular plants have also been relatively little studied in comparison
with vascular plants. About half of the 1013 species of lichens and associated fungi of British Columbia have been reported from five or fewer
sites (Goward, 1991). Although many of these species may indeed be