| dc.description.abstract | Larix Iyallii Parl, (alpine larch) is a small to medium tree
restricted to the timberline zone of the mountainous regions
of the Pacific Northwest of the United States and the adjacent
southwest of Canada. To examine the pattern of phenotypic
variation expressed in alpine larch cones and needles, field
collections were made in 1985 and 1986 from 11 populations
covering most of the species' range. Additionally, samples
were collected from 6 populations of L. occidentalis Nutt,
(western larch) to compare these two closely related species.
Morphometric analyses were based on 45 needle and 11
cone characters. Alpine larch cones averaged 32.2 mm in
length, 14.8 mm in diameter and possessed close to 50 cone
scales. Short shoot needles were 26.0 mm long, 0.7 mm wide
and 0.5 mm thick. An average of 7.8 epithelial cells
surrounded each of the two resin canals In the needles.
Both principal component analysis (PCA) and discriminant
analysis (DA) distinguished the two species. PCA of the alpine
larch needle data indicated limited differentiation between
populations. The principal components could not be correlated
to latitude, longitude or elevation. DA variation expressed in
the needle and cone characters was difficult to interpret:
neighbouring populations were often more distinct than
distant ones. Microgeographic variation in site and climate may influence alpine larch populations to such an extent that
broad geographic patterns, if present, were not detectable.
Alternatively, genetic drift may be responsible for the
variation displayed. Overall, phenotypic variation within L.
Iyallli appears to be less than that observed In L. occldentalis.
The general methodology used to examine alpine and
western larch populations was applied to herbarium specimens
made from the living collection of larches of the Arnold
Arboretum of Harvard University, representing 7 of the 10
recognized species of Larix Mill. Based on the limited number
of samples available, DA correctly classified all specimens
Into their correct species groups. The expressed pattern of
variation was loosely associated with the geographic
distribution of the species. DA, and PCA, also distinguished,
and thus provided some support for, the two proposed sections
of Larix. Multiserlales Patschke and Pauciseriales Patschke. | |
