A morphometric study of geographic variation in the snowshoe hare (Lepus americanus)

1985 ◽  
Vol 63 (3) ◽  
pp. 567-579 ◽  
Author(s):  
David W. Nagorsen
Keyword(s):  
North America ◽  
Great Lakes ◽  
Geographic Variation ◽  
Principal Component ◽  
Lepus Americanus ◽  
Morphometric Study ◽  
Western North America ◽  
Environmental Selection ◽  
Local Selection ◽  
Central Canada

Geographic variation in Lepus americanus was studied by multivariate analyses of 15 cranial measurements. A total of 1494 specimens from the entire geographic range were grouped into 37 geographic samples of males and females. Principal component analyses demonstrated that hares are largest in eastern North America, Alaska, and northwestern Canada, and smallest in the Pacific Northwest. Size clines exist in the Appalachian Mountains and western North America but size is relatively uniform throughout central Canada and the Great Lakes. A multiple regression of size with 16 climatic variables factors demonstrated that size and climate are strongly correlated; the size trends may reflect environmental selection. The differentiation of hares from the western Cordillera and Pacific coast, the similarity of populations from central Canada and the Great Lakes, and the clines in the Appalachians and western North America were evident in discriminant analyses. These patterns of variation among populations can be attributed to both gene flow and local selection. There is no evidence from the morphometric analyses for classifying populations into the 15 subspecies currently recognized.

Geographic Variation in Fluted Projectile Points: A Hemispheric Perspective

1999 ◽  
Vol 64 (2) ◽  
pp. 215-230 ◽  
Author(s):  
Juliet E. Morrow ◽  
Toby A. Morrow
Keyword(s):  
North America ◽  
South America ◽  
Geographic Variation ◽  
Great Plains ◽  
North American ◽  
South American ◽  
Western North America ◽  
Radiocarbon Dates ◽  
Projectile Points ◽  
Fluted Points

This paper examines geographic variation in fluted point morphology across North and South America. Metric data on 449 North American points, 31 Central American points, and 61 South American points were entered into a database. Ratios calculated from these metric attributes are used to quantify aspects of point shape across the two continents. The results of this analysis indicate gradual, progressive changes in fluted point outline shape from the Great Plains of western North America into adjacent parts of North America as well as into Central and South America. The South American “Fishtail” form of fluted point is seen as the culmination of incremental changes in point shape that began well into North America. A geographically gradual decline in fluting frequency also is consistent with the stylistic evolution of the stemmed “Fishtail” points. Although few in number, the available radiocarbon dates do suggest that “Fishtail” fluted points in southern South America are younger than the earliest dates associated with Clovis points in western North America. All of these data converge on the conclusion that South American “Fishtail” points evolved from North American fluted points.

scholarly journals Changes toward Earlier Streamflow Timing across Western North America

2005 ◽  
Vol 18 (8) ◽  
pp. 1136-1155 ◽  
Author(s):  
Iris T. Stewart ◽  
Daniel R. Cayan ◽  
Michael D. Dettinger
Keyword(s):  
North America ◽  
Large Scale ◽  
Center Of Mass ◽  
Principal Component ◽  
Warming Trend ◽  
Western North America ◽  
Climate Fluctuations ◽  
Climate Indicators ◽  
Decadal Scale ◽  
Streamflow Timing

Abstract The highly variable timing of streamflow in snowmelt-dominated basins across western North America is an important consequence, and indicator, of climate fluctuations. Changes in the timing of snowmelt-derived streamflow from 1948 to 2002 were investigated in a network of 302 western North America gauges by examining the center of mass for flow, spring pulse onset dates, and seasonal fractional flows through trend and principal component analyses. Statistical analysis of the streamflow timing measures with Pacific climate indicators identified local and key large-scale processes that govern the regionally coherent parts of the changes and their relative importance. Widespread and regionally coherent trends toward earlier onsets of springtime snowmelt and streamflow have taken place across most of western North America, affecting an area that is much larger than previously recognized. These timing changes have resulted in increasing fractions of annual flow occurring earlier in the water year by 1–4 weeks. The immediate (or proximal) forcings for the spatially coherent parts of the year-to-year fluctuations and longer-term trends of streamflow timing have been higher winter and spring temperatures. Although these temperature changes are partly controlled by the decadal-scale Pacific climate mode [Pacific decadal oscillation (PDO)], a separate and significant part of the variance is associated with a springtime warming trend that spans the PDO phases.

Geographic Variation of the Screech Owls of the Deserts of Western North America

The Condor ◽  
1951 ◽  
Vol 53 (4) ◽  
pp. 161-177 ◽  
Author(s):  
Alden H. Miller ◽  
Loye Miller
Keyword(s):  
North America ◽  
Geographic Variation ◽  
Western North America

Morphometrics and Redescription of Aphyllon fasciculatum and Aphyllon franciscanum, Two Widespread but Previously Conflated Species in Western North America

2021 ◽  
Vol 46 (2) ◽  
pp. 446-455
Author(s):  
Adam C. Schneider ◽  
Ben E. Benton
Keyword(s):  
North America ◽  
Principal Component ◽  
Calyx Lobe ◽  
Corolla Tube ◽  
Herbarium Specimens ◽  
Western North America ◽  
Widespread Species ◽  
Floral Color ◽  
Discriminant Analyses ◽  
Floral Characters

Abstract— We continue the taxonomic reevaluation of Aphyllon sect. Aphyllon by describing a widespread species throughout western North America previously recognized within a polyphyletic A. fasciculatum. To support our description and revised key, we analyzed fifteen continuous and discrete characters sampled from 186 herbarium specimens and iNaturalist observations representing the geographic and host ranges. Principal component and multiple correspondence analyses reveal clear variation in floral characters. Discriminant analyses show that three aspects of floral color, corolla lobe tip shape, the calyx cup to calyx lobe ratio, calyx lobe length, and degree of bend in the corolla tube are useful distinguishing features, but not diagnostic in every case.

scholarly journals Barrier to Gene Flow Between Eastern and Western Populations of Cronartium ribicola in North America

2000 ◽  
Vol 90 (10) ◽  
pp. 1073-1078 ◽  
Author(s):  
R. C. Hamelin ◽  
R. S. Hunt ◽  
B. W. Geils ◽  
G. D. Jensen ◽  
V. Jacobi ◽  
...  
Keyword(s):  
Gene Flow ◽  
New Mexico ◽  
North America ◽  
Random Amplified Polymorphic Dna ◽  
Principal Component ◽  
Genetic Distances ◽  
Group Method ◽  
Cronartium Ribicola ◽  
Western North America ◽  
Pair Group

The population structure of Cronartium ribicola from eastern and western North America was studied to test the null hypothesis that populations are panmictic across the continent. Random amplified polymorphic DNA markers previously characterized in eastern populations were mostly fixed in western populations, yielding high levels of genetic differentiation between eastern and western populations (φst = 0.55; θ = 0.36; P < 0.001). An unweighted pair-group method, arithmetic mean dendro-gram based on genetic distances separated the four eastern and four western populations into two distinct clusters along geographic lines. Similarly, a principal component analysis using marker frequency yielded one cluster of eastern populations and a second cluster of western populations. The population from New Mexico was clearly within the western cluster in both analyses, confirming the western origin of this recent introduction. This population was completely fixed (Hj = 0.000; n = 45) at all loci suggesting a severe recent population bottleneck. Genetic distances were low among populations of western North America (0.00 to 0.02) and among eastern populations (0.00 to 0.02), indicating a very similar genetic composition. In contrast, genetic distances between eastern and western populations were large, and all were significantly different from 0 (0.07 to 0.19; P < 0.001). Indirect estimates of migration were high among western populations, including the number of migrants among pairs of populations (Nm > 1) between New Mexico and British Columbia populations, but were smaller than one migrant per generation between eastern and western populations. These results suggest the presence of a barrier to gene flow between C. ribicola populations from eastern and western North America.

scholarly journals Northern Hemisphere Modes of Variability and the Timing of Spring in Western North America

2011 ◽  
Vol 24 (15) ◽  
pp. 4003-4014 ◽  
Author(s):  
Toby R. Ault ◽  
Alison K. Macalady ◽  
Gregory T. Pederson ◽  
Julio L. Betancourt ◽  
Mark D. Schwartz
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
Principal Component ◽  
Reanalysis Data ◽  
Onset Date ◽  
Western North America ◽  
Spatial And Temporal Patterns ◽  
Modes Of Variability ◽  
Index Model ◽  
Maximum Temperatures

Abstract Spatial and temporal patterns of variability in spring onset are identified across western North America using a spring index (SI) model based on weather station minimum and maximum temperatures (Tmin and Tmax, respectively). Principal component analysis shows that two significant and independent patterns explain roughly half of the total variance in the timing of spring onset from 1920 to 2005. However, these patterns of spring onset do not appear to be linear responses to the primary modes of variability in the Northern Hemisphere: the Pacific–North American pattern (PNA) and the northern annular mode (NAM). Instead, over the period when reanalysis data and the spring index model overlap (1950–2005), the patterns of spring onset are local responses to the state of both the PNA and NAM, which together modulate the onset date of spring by 10–20 days on interannual time scales. They do so by controlling the number and intensity of warm days. There is also a regionwide trend in spring advancement of about −1.5 days decade−1 from 1950 to 2005. Trends in the NAM and PNA can only explain about one-third (−0.5 day decade−1) of this trend.

scholarly journals Whole-genome analysis of introgression between the spotted owl and barred owl (Strix occidentalis and Strix varia, respectively; Aves: Strigidae) in western North America

2018 ◽  
Author(s):  
Zachary R. Hanna ◽  
John P. Dumbacher ◽  
Rauri C.K. Bowie ◽  
James B. Henderson ◽  
Jeffrey D. Wall
Keyword(s):  
North America ◽  
Sequence Data ◽  
Whole Genome Sequence ◽  
Whole Genome ◽  
Western North America ◽  
Whole Genome Analysis ◽  
Spotted Owl ◽  
Strix Varia ◽  
Local Selection ◽  
Spotted Owls

AbstractAs the barred owl (Strix varia; Aves: Strigiformes: Strigidae) expands throughout western North America, hybridization between barred and spotted owls (Strix varia and S. occidentalis, respectively), if abundant, may lead to genetic swamping of the endangered spotted owl. We analyzed low-coverage, whole-genome sequence data from fifty-one barred and spotted owls to investigate recent introgression between these two species. Although we obtained genomic confirmation that these species can and do hybridize and backcross, we found no evidence of widespread introgression. Plumage characteristics of western S. varia that suggested admixture with S. occidentalis appear unrelated to S. occidentalis ancestry and may instead reflect local selection.

Morphometric variation within and between populations of the pine aphid, Cinara nigra (Wilson) (Homoptera: Aphidoidea: Lachnidae), in western North America

1990 ◽  
Vol 68 (7) ◽  
pp. 1410-1419 ◽  
Author(s):  
R. G. Foottit ◽  
M. Mackauer
Keyword(s):  
North America ◽  
Morphological Variation ◽  
Pinus Contorta ◽  
Principal Component ◽  
Significant Loss ◽  
Population Variation ◽  
Species Discrimination ◽  
Western North America ◽  
Shape Variation ◽  
Morphometric Variation

Morphological variation in Cinara nigra (Wilson), found on Pinus contorta Dougl. ex Loud, throughout western North America, was characterized with the aid of univariate and multivariate statistical methods. Within-population variation in one sample collected near Edson, Alberta, was examined. Correlation and principal component analysis revealed patterns of interdependence among characters as well as patterns of size and size-related shape variation in 52 characters. To examine morphological variation between 19 geographic samples, this initial set was reduced in two steps to 49 and 32 characters, respectively; the reduction did not result in a significant loss of information content. No geographic pattern in clusters of samples was revealed either by the ordination of sample centroids or by UPGMA cluster analysis of the Mahalanobis D values. The taxonomic implications of this morphometric analysis are discussed, in particular the usefulness of various morphological attributes for species discrimination.

Revision of the Aster lanceolatus complex, including A. simplex and A. hesperius (Compositae: Astereae): a multivariate morphometric study

1987 ◽  
Vol 65 (5) ◽  
pp. 1047-1062 ◽  
Author(s):  
John C. Semple ◽  
Jerry G. Chmielewski
Keyword(s):  
North America ◽  
Morphological Variation ◽  
Multivariate Analyses ◽  
Single Species ◽  
Morphometric Study ◽  
Eastern North America ◽  
Western North America ◽  
Reproductive Structures ◽  
Infraspecific Taxa ◽  
Typical Variety

The complex is treated as a single species, Aster lanceolatus, on the basis of fieldwork, garden studies, herbarium work, and multivariate analyses of morphological variation of reproductive structures among 200 representative specimens. Two subspecies are recognized: ssp. hesperius occurring in western North America and ssp. lanceolatus occurring in central and eastern North America. Subspecies lanceolatus is further divided into four varieties: var. hirsuticaulis, var. interior, var. lanceolatus (including A. simplex), and var. latifolius. The typical variety is the most diverse and is considered to include forms most like the ancestor of the species. A key to the five infraspecific taxa is presented along with full synonymy. The following new names and combinations are proposed: Aster lanceolatus ssp. hesperius, A. lanceolatus ssp. lanceolatus var. hirsuticaulis, A. lanceolatus ssp. lanceolatus var. interior, and A. lanceolatus ssp. lanceolatus var. latifolius.

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