Abiotic constraints on the competitive ability of exotic and native grasses in a Pacific
Northwest prairie.Preview By: Pfeifer-Meister, Laurel; Cole, Esther M.; Roy, Bitty A.;
Bridgham, Scott D.. Oecologia, Feb2008, Vol. 155 Issue 2, p357-366, 10p, 2 charts, 5
graphs; DOI: 10.1007/s00442-007-0909-6; (AN 29983708)
Abstract:
In prairie ecosystems, abiotic constraints on competition can structure plant communities;
however, the extent to which competition between native and exotic plant species is
constrained by environmental factors is still debated. The objective of our study was to
use paired field and greenhouse experiments to evaluate the competitive dynamics
between two native ( Danthonia californica and Deschampsia cespitosa) and two exotic (
Schedonorus arundinaceus and Lolium multiflorum) grass species under varying nutrient
and moisture conditions in an upland prairie in the Willamette Valley, Oregon. We
hypothesized the two invasive, exotic grasses would be more competitive under highnutrient, moderate-moisture conditions, resulting in the displacement of native grasses
from these environments. In the field, the experimental reduction of competition resulted
in shorter, wider plants, but only the annual grass, Lolium multiflorum, produced more
aboveground biomass when competition was reduced. In the greenhouse, the two exotic
grasses produced more total biomass than the two native grasses. Competitive hierarchies
were influenced by nutrient and/or moisture treatments for the two exotic grasses, but not
for the two native grasses. L. multiflorum dominated competitive interactions with all
other grasses across treatments. In general, S. arundinaceus dominated when in
competition with native grasses, and D. cespitosa produced the most biomass in
monoculture or under interspecific competition with the other native grass, D. californica.
D. californica, D. cespitosa, and S. arundinaceus all produced more biomass in highmoisture, high-nutrient environments, and D. cespitosa, L. multiflorum, and S.
arundinaceus allocated more biomass belowground in the low nutrient treatment. Taken
together, these experiments suggest the competitive superiority of the exotic grasses,
especially L. multiflorum, but, contrary to our hypothesis, the native grasses were not
preferentially excluded... [ABSTRACT FROM AUTHOR]
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Author Affiliations:
1Center for Ecology and Evolutionary Biology, University of Oregon, Eugene, OR
97403, USA
ISSN:
00298549
DOI:
10.1007/s00442-007-0909-6
Accession Number:
29983708
Biotic interactions and plant invasions. Has a PDF
By: Mitchell, Charles E.; Agrawal, Anurag A.; Bever, James D.; Gilbert, Greogory S.; Hufbauer, Ruth
A.; Klironomos, John N.; Maron, John L.; Morris, William F.; Parker, Ingrid M.; Power, Alison G.;
Sealbloom, Eric W.; Torchin, Mark E.; Vázquez, Diego P.. Ecology Letters, Jun2006, Vol. 9 Issue 6,
p726-740, 15p, 2 charts, 1 diagram, 2 graphs; DOI: 10.1111/j.1461-0248.2006.00908.x; (AN
20857584)
Introduced plant populations lose interactions with enemies, mutualists and competitors
from their native ranges, and gain interactions with new species, under new abiotic
conditions. From a biogeographical perspective, differences in the assemblage of
interacting species, as well as in abiotic conditions, may explain the demographic success
of the introduced plant populations relative to conspecifics in their native range. Within
invaded communities, the new interactions and conditions experienced by the invader
may influence both its demographic success and its effects on native biodiversity. Here,
we examine indirect effects involving enemies, mutualists and competitors of introduced
plants, and effects of abiotic conditions on biotic interactions. We then synthesize ideas
building on Darwin's idea that the kinds of new interactions gained by an introduced
population will depend on its relatedness to native populations. This yields a heuristic
framework to explain how biotic interactions and abiotic conditions influence invader
success. We conclude that species introductions generally alter plants’ interactions with
enemies, mutualists and competitors, and that there is increasing evidence that these
altered interactions jointly influence the success of introduced populations. [ABSTRACT
FROM AUTHOR]
Copyright of Ecology Letters is the property of Blackwell Publishing Limited and its content may not be
copied or emailed to multiple sites or posted to a listserv without the copyright holder's express
written permission. However, users may print, download, or email articles for individual use. This
abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to
the original published version of the material for the full abstract. (Copyright applies to all
Abstracts)
Natural and land-use history of the Northwest mountain ecoregions (USA) in relation to
patterns of plant invasions.
Preview
By: Parks, Catherine G.; Radosevich, Steven R.; Endress, Bryan A.; Naylor, Bridgett J.;
Anzinger, Dawn; Rew, Lisa J.; Maxwell, Bruce D.; Dwire, Kathleen A.. Perspectives in Plant Ecology,
Evolution & Systematics, Dec2005, Vol. 7 Issue 3, p137-158, 22p; DOI: 10.1016/j.ppees.2005.09.007;
(AN 19045253)
Abstract: Although the Northwest currently has the least proportion of non-native
invasive plant species relative to other regions of North America, invasions continue to
increase into the mountainous areas of the region. Landscape structure, such as the
variation found along the complex gradients of the Northwest mountain ecoregions,
affects the expansion of invasive plant species and the invasibility of plant communities.
Also, the history of land use and current use patterns affect the expansion of invasive
plants, and many of the deteriorated environments in the region's mountains may invite
and stabilize plant invasions. We examined the patterns of invasive plant diversity in
Northwest mountain ecoregions, as derived from literature sources, to analyze which
factors influence plant invasions. Our analysis found altered riparian systems and
disturbed forests to be especially vulnerable to plant invasion. Conversely, alpine and
wilderness areas are still relatively unaffected by invasive plants. Both riparian and
alpine communities, while making up a relatively small area across Northwest mountain
ecoregions, have significant ecological importance and deserve special protection from
invasive plant introductions. Human settlement at low elevations and intense land use of
upland forests will likely continue to enhance invasive plant introductions into Northwest
mountain ecosystems. Knowledge of the relationships between biological and
environmental factors, disturbance, and human land use will be critical for future
management strategies that proactively locate, prevent, or contain plant invasions in the
mountains of the Northwest. [Copyright 2005 Elsevier]
Copyright of Perspectives in Plant Ecology, Evolution & Systematics is the property of
Elsevier Science and its content may not be copied or emailed to multiple sites or posted
to a listserv without the copyright holder's express written permission. However, users
may print, download, or email articles for individual use. This abstract may be abridged.
No warranty is given about the accuracy of the copy. Users should refer to the original
published version of the material for the full abstract. (Copyright applies to all Abstracts)
Evaluation of Rubus leucodermis Populations from the Pacific Northwest.
Preview
By: Finn, Chad; Wennstrom, Kirsten; Link, Janessa; Ridout, Jill. HortScience, Oct2003, Vol.
38 Issue 6, p1169-1172, 4p, 2 charts; (AN 12686474)
Sixteen western black raspberry (Rubus leucodermis Douglas ex Torrey & A. Gray)
populations, collected from throughout the Pacific Northwest, and 'Munger', the most
widely grown black raspberry (R. occidentalis L.) cultivar, were established in 1994 in a
replicated trial in Corvallis, Ore. In 1996 and 1997 the seedlings were evaluated for date
of budbreak, flowering date, ripening date, fruit size, and disease tolerance. Fruit within a
replication were pooled for evaluation of pH, soluble solids, titratable acidity, and
anthocyanin content. The plants were vigorous and had produced solid hedges by the
time evaluation commenced. The populations were significantly different within each
year for all traits except for anthocyanin content in 1996. Rubus leucodermis populations
were identified that broke bud and ripened fruit earlier or later than 'Munger'; however,
all flowered with or sooner than 'Munger'. Despite the fact that R. occidentalis is native to
eastern North America and R. leucodermis to the West, 'Munger' was much less affected
by foliar and cane diseases than the R. leucodermis populations. Several populations were
as vigorous as 'Munger'. 'Munger' had fruit that were 30% larger than the mean for any R.
leucodermis population. Generally, R. leucodermis had higher pH and lower titratable
acidity than 'Munger', but many populations had similar soluble solids; lower acidity may
partly explain the blandness of R. leucodermis fruit compared with 'Munger'. Despite the
lighter appearance of R. leucodermis, the anthocyanin levels of some populations were
higher than 'Munger'. Rubus leucodermis may be a source of earlier fruiting, later
budbreak, and vigor when used in breeding but careful selection for fruit size (for the
fresh market), acidity (for the processing market), and disease resistance must be done.
Rubus leucodermis may also be an excellent source of raspberry bushy dwarf virus
(RBDV) resistance in black and red raspberry breeding programs. [ABSTRACT FROM
AUTHOR]
Initial Effects of Prescribed Fire on Morphology, Abundance, and Phenology of Forbs in
Big Sagebrush Communities in Southeastern Oregon.
Preview
By: Wrobleski, David W.; Kauffman, J. Boone. Restoration Ecology, Mar2003, Vol. 11 Issue
1, p82-90, 9p; DOI: 10.1046/j.1526-100X.2003.00084.x; (AN 9133079)
Abstract Historic fire return intervals in Artemesia tridentata (big sagebrush) ecosystems
have been altered by livestock grazing, fire suppression, and other land management
techniques resulting in ecological changes in these areas. Increases in abundance of
woody vegetation may be causing declines in native herbaceous understory species. We
examined the effects of prescribed fire on the morphology, abundance, and phenology of
nine abundant forb (herbaceous dicot) species used selectively by Centrocercus
urophasianus (Sage Grouse). In September 1997 prescribed fire was applied to four of
eight randomly assigned 400-ha A.t. wyomingensis (Wyoming big sagebrush) study plots
at Hart Mountain National Antelope Refuge, Oregon. Livestock had not grazed
experimental plots since 1991. Burning caused morphological changes such as
significantly greater numbers of racemes and flowers per raceme in Astragalus malachus
(shaggy milkvetch-Legumoideae) (9 in burn vs. 6 in control; 23 in burn vs. 21 in control,
respectively). Also, prescribed burning caused greater numbers of flowers in Phlox
gracilis (microsteris-Polemoniaceae) (57 vs. 13), greater numbers of umbels and
umbelletts in Lomatium nevadense (Nevada desert parsley-Umbellifereae) (4 vs. 2 and 59
vs. 31, respectively), greater numbers of flower heads in Crepis modocensis (Modoc
hawksbeard-Compositae) (32 vs. 21), and greater number of flowers/cm³ in
Phlox longifolia (longleaf phlox-Polemoniaceae) (0.11 vs. 0.06). Crown volume of
Crepis modocensis (7,085 vs. 4,179 cm³ ) and Astragalus malachus (2,854
vs. 1,761 cm³ ) plants was greater in burned plots than control plots.
However, burning resulted in a smaller crown area of Antennaria dimorpha (low
pussytoes-Compositae) (20 vs. 37 cm² ). Phenology and time of flowering
were also affected by fire. The period of active growth for each species was extended
later into the summer in burned plots ( p < 0.01). In addition, Crepis... [ABSTRACT
FROM AUTHOR]
Prescribed Fire and the Response of Woody Species in Willamette Valley Wetland
Prairies.Preview By: Pendergrass, K. L.; Miller, P. M.; Kauffman, J. B.. Restoration
Ecology, Sep98, Vol. 6 Issue 3, p303-311, 9p, 5 charts; DOI: 10.1046/j.1526100X.1998.06311.x; (AN 6146909)
A single fall-season prescribed burn and two consecutive fall-season prescribed burns
were conducted in 1988 and 1989 to quantify the effects of fire intensity and frequency
on woody species in two Willamette Valley wet prairies. Fuel biomass, fuel properties,
fire behavior, biomass consumption, and changes in woody species density and height
were documented before and after the burns. Before burning, Rosa nutkana (Nootka rose)
was the most abundant woody species at both sites. In 1988, burns were significantly
more intense, produced more heat per unit area at Fisher Butte than at Rose Prairie, and
were fairly complete, with 37% and 35% woody biomass consumption, respectively. In
1989, burns were spotty; only 11% of woody biomass was consumed at Fisher Butte. The
one-burn treatment did not affect R. nutkana density in 1 × 15 m transects at either site;
the two-burn treatment significantly increased its density in three of the five communities
sampled. Burning significantly reduced height growth by eliminating taller individuals
while stimulating sprouts from belowground tissues. Redistribution of R. nutkana and
trees into shorter height classes indicates the possibility of reducing the visual dominance
of woody species if periodic burns were conducted in native Willamette Valley prairie.
The low-intensity burns in this study were sufficient to remove the woody shoots under 3
m tall but did not reduce their capacity to regenerate and did not reduce the density of
woody species. After decades of fire suppression, two burns were not sufficient to
reestablish the desired balance between native herbaceous and woody species or to
reduce the presence of introduced woody species. A long-term commitment to the
reintroduction of fire as a management tool will be required to maintain native wetland
prairies in the Willamette Valley. [ABSTRACT FROM AUTHOR]
Copyright of Restoration Ecology is the property of Blackwell Publishing Limited and its
content may not be copied or emailed to multiple sites or posted to a listserv without the
copyright holder's express written permission. However, users may print, download, or
email articles for individual use. This abstract may be abridged. No warranty is given
about the accuracy of the copy. Users should refer to the original published version of the
material for the full abstract. (Copyright applies to all Abstracts)
Crop Damage Estimates for Crown Rot of Wheat and Barley in the Pacific Northwest.
Preview By: Smiley, Richard W.; Gourlie, Jennier A.; Easley, Sandra A.; Patterson, LisaMarie; Whittaker, Ruth G.. Plant Disease, Jun2005, Vol. 89 Issue 6, p595-604, 10p, 7
charts, 2 graphs; DOI: 10.1094/PD-89-0595; (AN 17175145)
Crown rot of wheat and barley in the Pacific Northwest is caused by a complex of
Fusarium pseudograminearum, F. culmorum, F. avanaceum, Bipolaris sorokniana, and
Microdochium nivale. Yield-loss estimates were made by evaluating yield components
on tillers collected from commercial fields and sorted by disease severity classes, and by
comparing yields for field plots inoculated with F. pseudograminearum with yields in
naturally infested soil. Increasing crown rot severity caused an increase in grain protein
content and reduction in grain yield, kernels per head, kernel weight, test weight, tiller
height, and straw weight. Crown rot reduced winter wheat yield as much as 1,550 kg/ha
(35%, $219/ha) in commercial fields, with a 13-field mean of 9.5% ($51/ha). Inoculation
reduced yields as much as 2,630 kg/ha (61%, $372/ha) over that caused by the native
pathogen flora. Rain-induced crusting of the soil surface greatly amplified pre-emergence
damping-off caused by F. pseudograminearum. Crown rot caused the greatest losses
during seasons of lowest precipitation but also damaged crops under wet conditions.
Aboveground symptoms were not always apparent under conditions of moderate
infection and yield constraint. Damage from crown rot in the Pacific Northwest is more
widespread and damaging than previously recognized. [ABSTRACT FROM AUTHOR]
Copyright of Plant Disease is the property of American Phytopathological Society and its
content may not be copied or emailed to multiple sites or posted to a listserv without the
copyright holder's express written permission. However, users may print, download, or
email articles for individual use. This abstract may be abridged. No warranty is given
about the accuracy of the copy. Users should refer to the original published version of the
material for the full abstract. (Copyright applies to all Abstracts)
Fire and Litter Effects on Seedling Establishment in Western Oregon Upland
Prairies.Preview By: Maret, Mary P.; Wilson, Mark V.. Restoration Ecology, Sep2005,
Vol. 13 Issue 3, p562-568, 7p; DOI: 10.1111/j.1526-100X.2005.00071.x; (AN 17922515)
PDF Full Text (86KB)
Prescribed burning is an important tool for managing and restoring prairies and other
ecosystems. One effect of fire is plant litter removal, which can influence seedling
establishment. Four experimental treatments (burned, clipped and raked to remove litter,
burned with litter reapplied, and unmanipulated) were applied to 2 × 2.5–m plots in three
western Oregon, United States, upland prairies to determine how burning affects seedling
establishment. Seeds of common exotic and native prairie species were sowed into the
experimental plots after treatments. Seedlings were censused the following spring. The
experiment was repeated on each of the three sites, representing three common types of
prairie vegetation: an Annual Exotic Grass site, a Perennial Exotic Grass site, and a
Native Bunchgrass site. In both the Annual Exotic Grass and the Perennial Exotic Grass
sites, burning significantly improved native, but not exotic, seedling establishment over
those on unburned plots. Litter removal was a significant component of this burn effect,
particularly on the Perennial Exotic Grass site. In these winter-moist systems, the net
effect of litter is to inhibit seedling establishment. Burning treatments on the Native
Bunchgrass site significantly increased seedling establishment only of short-lived exotic
species. These results suggest that in prairie ecosystems similar to the Annual and
Perennial Exotic Grass sites, prescribed burning followed by sowing native seeds can be
an effective restoration technique. Burning alone or sowing alone would be counterproductive, in the first case because increased establishment would come from exotic
species and in the second case because establishment rates are low in unburned plots.
[ABSTRACT FROM AUTHOR]
Copyright of Restoration Ecology is the property of Blackwell Publishing Limited and its
content may not be copied or emailed to multiple sites or posted to a listserv without the
copyright holder's express written permission. However, users may print, download, or
email articles for individual use. This abstract may be abridged. No warranty is given
about the accuracy of the copy. Users should refer to the original published version of the
material for the full abstract. (Copyright applies to all Abstracts)
WEB SREACHS
NATIVE WILLAMETTE VALLEY PRAIRIE RESTORATION
http://www.oregonoaks.org/documents/prairierestinfo.html
Landmarks of botanical history
http://isbndb.com/d/book/landmarks_of_botanical_history.html
Full text of "Publications of the Bureau of Plant Industry"
http://www.archive.org/stream/bureauofplantind00unitiala/bureauofplantind00unitiala_dj
vu.txt
PDF]
PATTERNS OF RARITY IN THE OREGON FLORA: IMPLICATIONS FOR
CONSERVATION ...
http://www.appliedeco.org/reports/rarity_in_oregon.pdf
Oregon Flora Project
www.oregonflora.org
[PDF]
RESTORING RARE NATIVE HABITATS IN THE WILLAMETTE VALLEY
www.ser.org/sernw/pdf/DefOWild_willamette_hab_restore_manual.pdf
New Strings
Crop Damage Estimates for Crown Rot of Wheat and Barley in the Pacific Northwest.
Preview By: Smiley, Richard W.; Gourlie, Jennier A.; Easley, Sandra A.; Patterson, LisaMarie; Whittaker, Ruth G.. Plant Disease, Jun2005, Vol. 89 Issue 6, p595-604, 10p, 7
charts, 2 graphs; DOI: 10.1094/PD-89-0595; (AN 17175145)
Crown rot of wheat and barley in the Pacific Northwest is caused by a complex of
Fusarium pseudograminearum, F. culmorum, F. avanaceum, Bipolaris sorokniana, and
Microdochium nivale. Yield-loss estimates were made by evaluating yield components
on tillers collected from commercial fields and sorted by disease severity classes, and by
comparing yields for field plots inoculated with F. pseudograminearum with yields in
naturally infested soil. Increasing crown rot severity caused an increase in grain protein
content and reduction in grain yield, kernels per head, kernel weight, test weight, tiller
height, and straw weight. Crown rot reduced winter wheat yield as much as 1,550 kg/ha
(35%, $219/ha) in commercial fields, with a 13-field mean of 9.5% ($51/ha). Inoculation
reduced yields as much as 2,630 kg/ha (61%, $372/ha) over that caused by the native
pathogen flora. Rain-induced crusting of the soil surface greatly amplified pre-emergence
damping-off caused by F. pseudograminearum. Crown rot caused the greatest losses
during seasons of lowest precipitation but also damaged crops under wet conditions.
Aboveground symptoms were not always apparent under conditions of moderate
infection and yield constraint. Damage from crown rot in the Pacific Northwest is more
widespread and damaging than previously recognized. [ABSTRACT FROM AUTHOR]
Copyright of Plant Disease is the property of American Phytopathological Society and its
content may not be copied or emailed to multiple sites or posted to a listserv without the
copyright holder's express written permission. However, users may print, download, or
email articles for individual use. This abstract may be abridged. No warranty is given
about the accuracy of the copy. Users should refer to the original published version of the
material for the full abstract. (Copyright applies to all Abstracts)
Eocene-Oligocene extinction and paleoclimatic change near Eugene, Oregon.Preview By:
Retallack, Gregory J.; Orr, William N.; Prothero, Donald R.; Duncan, Robert A.; Kester,
Paul R.; Ambers, Clifford P.. Geological Society of America Bulletin, Jul/Aug2004, Vol.
116 Issue 7/8, p817-839, 13p, 4 charts, 12 diagrams, 16 graphs, 1 map, 23 bw; DOI:
10.1130/B25281.1; (AN 14009990)
Thick ash-flow tuffs provide marker beds through fossiliferous Eocene and Oligocene
marine and non-marine sedimentary rocks near Eugene, Oregon. New mapping,
radiometric dating, and paleomagnetic stratigraphy of these tuffs and rocks now allow
dating of local fossil floras. The Comstock, Goshen, Rujada, and Willamette floras have
been widely used as evidence for Eocene-Oligocene climatic cooling and drying. Eocene
leaves from Comstock and Hobart Butte included such thermophilic taxa as Liquidambar.
The early Oligocene Goshen flora lacked Liquidambar but retained many thermophillc
species with large leaves that have entire margins and acuminate apices (drip tips). In
contrast, fossil leaves from later Oligocene Rujada and Willamette floras are small and
serrate, and most lack drip tips. Marine faunas also indicate climatic cooling and local
disappearance of thermophilic molluscs such as Anadara, Ficus, and Conus. Our dating
and compilation of plant and molluscan fossil occurrences indicate a steady rise in
species diversity from 46 Ma to maximal diversity of thermophilic taxa at 35-34 Ma, then
extinctions of 60% of plant species after 33.4 Ma and 32% of marine invertebrates after
33.2 Ma, both significantly postdating the Eocene-Oligocene boundary at 33.7 Ma. Plant
diversity rebounds during the early Oligocene, but marine invertebrates continue to
decline into the Oligocene in part due to the retreat of fully marine environments from the
Eugene area. Neither these data, nor evidence from coeval fossil plants and soils in
central Oregon, support the notion of a "Terminal Eocene Event," nor any other single,
abrupt paleoclimatic shift or extinction. The Eocene-Oligocene biotic and climatic
transition was drawn out over some 6 m.y. Abrupt forcings such as meteorite impacts or
volcanic eruptions are less likely explanations for cooling and diversity decline than longterm processes such as mountain building, changing ocean currents, or reorganization of
the carbon... [ABSTRACT FROM AUTHOR]
Copyright of Geological Society of America Bulletin is the property of Geological
Society of America and its content may not be copied or emailed to multiple sites or
posted to a listserv without the copyright holder's express written permission. However,
users may print, download, or email articles for individual use. This abstract may be
abridged. No warranty is given about the accuracy of the copy. Users should refer to the
original published version of the material for the full abstract. (Copyright applies to all
Abstracts)
Paleobotanical section.
Preview American Journal of Botany, Jun96 Abstracts Supplement, Vol. 83, p110, 1/3p;
(AN 9608050887)
Presents an abstract of the study `Trochodendron infructesence from the 15 Ma Succor
Creek flora in Oregon: A geographic and possibly temporal range extension,' by Patrick
F. Fields, presented during the 1996 Annual Meeting of the Botanical Society of America
at the University of Washington in Seattle, Washington.
[PDF]
HOLOCENE VEGETATION AND FIRE HISTORY OF THE FLORISTICALLY
DIVERSE ...
https://scholarsbank.uoregon.edu/xmlui/bitstream/handle/1794/7486/Doctoral_thesis_win
ter2008_Christy_Briles.pdf?sequence=1
JSTOR: Natural Floristic Areas of the Western United States
http://www.jstor.org/pss/2845260
Insights into the Biogeography of the Pacific Northwest of North America: Evidence
from the Phylogeography of Salix Melanopsis
Steven J. Brunsfeld1, Terry R. Miller1, and Bryan C. Carstens2,3
The disjunction of the mesic coniferous forests of the Pacific Northwest (PNW) has long
been of interest to biogeographers, and several hypotheses have been posed to explain the
disjunct distribution pattern. Analysis of intraspecific chloroplast DNA variation (1785
bp of matK and 400 bp of rpl16) in Salix melanopsis allows these hypotheses to be
tested. Our study confirmed the existence of three genetic races (uncorrected sequence
divergence ranged from 0.7-1.1%) within the species, which differ in distribution and
ecology. The mesic race, associated with mesic coniferous forests, was the focus of this
study. This race consists of two major lineages (uncorrected sequence divergence ranged
up to 0.28%), one of which is associated with an apparent glacial refugium south of
glaciation in the northern Rocky Mountains. The three haplotypes that comprise the first
lineage are largely segregated into separate river canyons that comprise the “Greater
Clearwater Refugium”. The other major lineage includes three haplotypes that occur
throughout the PNW, except in the core of the Clearwater refugium. Vicariance is
implicated in the origin of this latter lineage. Dispersal both before and during the
Holocene appears to have occurred: the colonization of the Cascade Range from the
Rocky Mountains, and later the dispersal of the Cascade haplotype into the area formerly
buried by Cordilleran ice. More limited dispersal of Rocky Mountain haplotypes has
resulted in contact zones with elevated haplotype diversity. The results of this study allow
us to refine previous phylogeographic hypotheses of the PNW. Phylogenetic relationships
within Salix sect. Longifoliae, the group that includes S. melanopsis, were also inferred.
The sequence data produced phylogenetic hypotheses that were congruent with those
obtained from an earlier analysis of cpDNA restriction site data.