Changes in the diversity structure of avian assemblages in North America

Aim To determine the major patterns of change in avian diversity structure over space and time at a local resolution and continental extent in non‐urban areas in North America. Location The contiguous United States and southern Canada. Methods We used 1673 North American Breeding Bird Survey (BBS) routes containing 547 terrestrial and aquatic species to estimate four diversity components: species richness, individual abundance, taxonomic distinctness and species evenness. We implemented three levels of analysis to examine changes in diversity structure on a yearly basis from 1968 to 2003: (1) a canonical analysis of discriminance, (2) a univariate analysis across BBS routes, and (3) a univariate analysis at individual BBS routes. We estimated changes in similarity in species composition over time between 470,730 BBS route pairs. We also estimated the level of human activity at BBS routes using three spatial anthropogenic databases. Results BBS routes were located in non‐urban areas in association with low nighttime light activity and moderately low human population densities. The analysis of diversity structure indicated the presence of two independent patterns: (1) a temporally consistent pattern defined by increasing species richness (12% increase from 1968 to 2003) associated with limited gains in taxonomic distinctness, and (2) an association between species abundance and evenness related to variability in abundance associated with the most abundant species. The similarity analysis indicated that BBS routes located closer to the Atlantic and the Pacific coasts of the United States experienced the strongest patterns of homogenization of species composition. Main conclusions Our results suggest that avian diversity structure has changed at the local scale in non‐urban areas in North America. However, there was no evidence for a consistent continent‐wide pattern. Instead, the evidence pointed to the presence of regional factors influencing diversity patterns. This study provides a foundation for more detailed investigations of the spatiotemporal and taxonomic details of these general patterns.     

Population structure of North American beluga whales (Delphinapterus leucas) based on nuclear DNA microsatellite variation and contrasted with the population structure revealed by mitochondrial DNA variation

Beluga whales ( Delphinapterus leucas ) in North American waters migrate seasonally between wintering areas in broken pack ice and summering locations in estuaries and other open water areas in the Arctic and sub-Arctic. Results from our previous investigation of beluga whale mitochondrial DNA (mtDNA) revealed genetic heterogeneity among beluga from different summering locations that was interpreted as representing a high degree of summering site philopatry. However, mtDNA is maternally inherited and does not reflect mating that may occur among beluga from different summering locations in wintering areas or during annual migrations. To test the possibility that breeding occurs among beluga from different summering locations, genetic variability at five nuclear DNA (nDNA) microsatellite loci was examined in the same animals tested in the mtDNA study. Beluga samples ( n = 640) were collected between 1984 and 1994 from 24 sites across North America, mostly during the summer. Whales from the various sites were categorized into eight summering locations as identified by mtDNA analysis, as well as four hypothesized wintering areas: Bering Sea, Hudson Strait (Hudson Strait, Labrador Sea, southwest Davis Strait), Baffin Bay (North Water, east Davis Strait), and St Lawrence River. Microsatellite allele frequencies indicated genetic homogeneity among animals from summering sites believed to winter together but differentiation among whales from some of the wintering areas. In particular, beluga from western North America (Bering Sea) were clearly distinguished from beluga from eastern North America (Hudson Strait, Baffin Bay, and St Lawrence River). Based upon the combined data set, the population of North American beluga whales was divided into two evolutionarily significant units. However, the population may be further subdivided into management units to reflect distinct groups of beluga at summering locations.     

Population structure of North American beluga whales (Delphinapterus leucas) based on nuclear DNA microsatellite variation and contrasted with the population structure revealed by mitochondrial DNA variation

Beluga whales ( Delphinapterus leucas ) in North American waters migrate seasonally between wintering areas in broken pack ice and summering locations in estuaries and other open water areas in the Arctic and sub-Arctic. Results from our previous investigation of beluga whale mitochondrial DNA (mtDNA) revealed genetic heterogeneity among beluga from different summering locations that was interpreted as representing a high degree of summering site philopatry. However, mtDNA is maternally inherited and does not reflect mating that may occur among beluga from different summering locations in wintering areas or during annual migrations. To test the possibility that breeding occurs among beluga from different summering locations, genetic variability at five nuclear DNA (nDNA) microsatellite loci was examined in the same animals tested in the mtDNA study. Beluga samples ( n = 640) were collected between 1984 and 1994 from 24 sites across North America, mostly during the summer. Whales from the various sites were categorized into eight summering locations as identified by mtDNA analysis, as well as four hypothesized wintering areas: Bering Sea, Hudson Strait (Hudson Strait, Labrador Sea, southwest Davis Strait), Baffin Bay (North Water, east Davis Strait), and St Lawrence River. Microsatellite allele frequencies indicated genetic homogeneity among animals from summering sites believed to winter together but differentiation among whales from some of the wintering areas. In particular, beluga from western North America (Bering Sea) were clearly distinguished from beluga from eastern North America (Hudson Strait, Baffin Bay, and St Lawrence River). Based upon the combined data set, the population of North American beluga whales was divided into two evolutionarily significant units. However, the population may be further subdivided into management units to reflect distinct groups of beluga at summering locations.     

Matriarchal genetic population structure of North American beluga whales Delphinapterus leucas (Cetacea: Monodontidae)

The North American beluga whale Delphinapterus leucas population has been divided into a number of putative geographical stocks based upon migration routes and areas of summer concentration. Nucleotide sequences of the mitochondrial DNA (mtDNA) control region were used to assess whether these geographical stocks are genetically distinct. Beluga whale samples from 25 sites were collected primarily from aboriginal subsistence hunts across North America from 1984 to 1994. Thirty-nine mtDNA haplotypes were identified in 628 beluga samples. No differences were found in the distribution of haplotypes between male and female beluga whales at any sampling site. These haplotypes segregated into two distinct assemblages in both a haplotype network and a neighbour-joining tree. The haplotype assemblages had a geographically disjunct distribution that suggests postglacial recolonization of the North American Arctic from two different refugia.
An analysis of molecular variance based on haplotype relationships and frequency indicated genetic heterogeneity among beluga whale summering groups ( P ≤ 0.001). Sequence divergence estimates between sampling sites also indicated geographical differentiation, particularly between samples taken at east Hudson Bay or St Lawrence River and the western or central Arctic. The results of this study show a high degree of philopatry to specific summering areas by this highly mobile animal.     

Comparing naturalized alien plants and recipient habitats across an east–west gradient in the Mediterranean Basin

Aim To investigate alien plant species invasion levels in different habitats and alien species traits by comparing the naturalized flora in different areas of the same biogeographical region. Location Spain, Italy, Greece and Cyprus. Methods Comparison of floristic composition, species traits and recipient habitats of naturalized alien neophytes across an east–west gradient comprising four countries in the European Mediterranean basin. Results A total of 782 naturalized neophytes were recorded; only 30 species were present in all four countries. Although floristic similarity is low, the four alien floras share the same patterns of growth form (mostly herbs), life cycle (mostly perennials) and life form (mostly therophytes, hemicryptophytes and phanerophytes). The majority of the recipient habitats were artificial. Wetlands were the natural habitats, with the highest numbers of naturalized species. Floristic similarity analyses revealed: (1) the highest floristic similarity between Italy and Spain, both of which were more similar to Greece than to Cyprus; (2) two groups of floristic similarity between habitat categories in each country (Greece–Cyprus and Italy–Spain); (3) a higher degree of homogenization in the plant assemblages in different habitats in Greece and Cyprus and a lower degree of homogenization in those in Italy and Spain; and (4) a higher degree of homogenization in artificial and natural fresh‐water habitats than in the other natural habitats. Main conclusions The floristic similarity of naturalized neophytes between the four countries is low, although the overall analysis indicates that the western group (Italy–Spain) is separated from the eastern group (Greece–Cyprus). Similar patterns emerged regarding the life‐history traits and recipient habitats. The artificial habitats and the natural wet habitats are those that are invaded most and display the greatest homogenization in all four countries. Coastal habitats display a lower degree of homogenization but a high frequency of aliens. Dry shrubs and rocky habitats display a lower degree of homogenization and a low frequency of aliens.     

Biogeographical patterns of rocky intertidal communities along the Pacific coast of North America

Aim Our aim in this paper is to present the first broad‐scale quantification of species abundance for rocky intertidal communities along the Pacific coast of North America. Here we examine the community‐level marine biogeographical patterns in the context of formerly described biogeographical regions, and we evaluate the combined effects of geographical distance and environmental conditions on patterns of species similarity across this region. Location Pacific coast of North America. Methods Data on the percentage cover of benthic marine organisms were collected at 67 rocky intertidal sites from south‐eastern Alaska, USA, to central Baja California Sur, Mexico. Cluster analysis and non‐metric multidimensional scaling were used to evaluate the spatial patterns of species similarity among sites relative to those of previously defined biogeographical regions. Matrices of similarity in species composition among all sites were computed and analysed with respect to geographical distance and long‐term mean sea surface temperature (SST) as a measure of environmental conditions. Results We found a high degree of spatial structure in the similarity of intertidal communities along the coast. Cluster analysis identified 13 major community structure ‘groups’. Although breaks between clusters of sites generally occurred at major biogeographical boundaries, some of the larger biogeographical regions contained several clusters of sites that did not group according to spatial position or identifiable coastal features. Additionally, there were several outliers – sites that grouped alone or with sites outside their region – for which localized features may play an important role in driving community structure. Patterns of species similarity at the large scale were highly correlated with geographical distance among sites and with SST. Importantly, we found community similarity to be highly correlated with long‐term mean SST while controlling for the effects of geographical distance. Main conclusions These findings reveal a high degree of spatial structure in the similarity of rocky intertidal communities of the north‐east Pacific, and are generally consistent with those of previously described biogeographical regions, with some notable differences. Breaks in similarity among clusters are generally coincident with known biogeographical and oceanographic discontinuities. The strong correlations between species similarity and both geographical position and SST suggest that both geography and oceanographic conditions have a large influence on patterns of intertidal community structure along the Pacific coast of North America.     

Northern circumpolar distribution of brackish-water plathelminths

The composition of brackish-water faunas on both sides of North America shows a high degree of similarity with the corresponding faunas in European brackish waters in terms of species of the Plathelminthes. Twenty species are common to both the Atlantic coast of Canada and Northern Europe; a further nine brackish-water plathelminths are common to the Pacific coast of Alaska and Europe; and two species occur in all three areas. These patterns of distribution must be regarded as the result of past or present connections between the American and European populations of brackish-water species. The most parsimonious explanation is the hypothesis that a species-rich community of brackish-water plathelminths has a northern circumpolar distribution.     

Population genetic analysis of safflower (Carthamus tinctorius; Asteraceae) reveals a Near Eastern origin and five centers of diversity

Analyses of genetic variation in crop gene pools are a powerful tool for investigating the origin and early evolution of crop lineages. Such analyses also have the potential to identify unique genetic resources for continued crop improvement. The oilseed crop safflower (Carthamus tinctorius) is believed to have been domesticated in the Fertile Crescent region, but up to 10 geographic centers of similarity throughout the world have been proposed based on morphology. Nuclear microsatellite analysis of accessions from each of the 10 proposed centers of similarity, as well as individuals of the progenitor species, suggested the presence of five genetic clusters (1, Europe; 2, Turkey-Iran-Iraq-Afghanistan; 3, Israel-Jordan-Syria; 4, Egypt-Ethiopia; and 5, the Far East-India-Pakistan). North American accessions, products of a secondary introduction from the native range, suggest that a subset of the native accessions harbor unique genetic diversity that could be useful in future breeding efforts. Overall, a Near Eastern origin of safflower was confirmed based on the genetic similarity between the progenitor and the Near Eastern safflower accessions, as well as previous archaeological finds. Genetic differentiation between geographical clusters of accessions is evident, although not to the degree proposed based on morphology.     

Biogeographic patterns in scaled chrysophytes from the east coast of North America

1. We assessed the distribution of scaled chrysophytes in fresh waters along 3200 km of the east coast of North America (29° to 48°N) to determine any biogeographic patterns in relation to chemical, physical, climatic and spatial variables. 2. Scaled chrysophytes were identified using scanning electron microscopy and counted from 264 waterbodies in nine regions (20 subregions). Eighteen chemical, physical and climate variables were determined for each waterbody. We used Sorensen’s similarity index and analysis of similarity (ANOSIM) to evaluate whether the floras differed between regions, subregions, glaciated and non‐glaciated areas, as well as within sets of waterbodies with similar chemical and physical characteristics but situated in different regions. Distance‐based linear modelling (DISTLM) was used to evaluate the relative importance of the chemical, physical and climate factors in explaining the variability in the assemblages of scaled chrysophytes, and the resulting models were visualised using redundancy analysis (RDA). 3. Significant differences in the flora were found between all regions and most subregions, and between glaciated and non‐glaciated areas. Significant differences were also recorded between waterbodies with similar chemical and physical characteristics but situated in different regions. Many species were abundant along specific sections of the latitudinal gradient, but lacking from others. A set of environmental variables explained significant and independent portions of the variation in scaled chrysophytes, with pH and mean minimum July temperature accounting for 20% of the total. 4. The distribution of scaled chrysophytes along the east coast of North America is not homogeneous and there are biogeographic patterns, despite apparent dispersal mechanisms (migratory birds and wind events) that might act to reduce differences between regions. Rather, differences exist even between neighbouring subregions containing sites with statistically similar chemical and physical attributes. Environmental variables clearly play a significant role in determining whether species will inhabit a given site. However, species were not always found in waterbodies likely to support growth, implicating inadequate dispersal, poor transportability or both.     

On genetic differentiation of the Pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> tilesius, 1810 (Gadiformes: Gadidae)

The variability of the Gmo3, Gmo34, Gmo35, and Pgmo32 DNA microsatellite loci in Pacific cod Gadus macrocephalus samples from different areas of the North Pacific was analyzed. The data obtained show that Pacific cod from the southern Kuril Islands significantly differs from the populations of the Bering Sea, the Sea of Okhotsk, and the coastal waters of Canada (the microsatellite loci Gmo3 and Pgmo32 bear the highest differentiating capacity). Despite the significant geographical remoteness of these areas from one another, the above three Pacific cod populations exhibit a high degree of similarity (I = 0.997–0.999).     

Comparative Insect Faunas between Ganghwado and Six others Islands of West Coastal in Incheon,Korea

This paper is intended as an investigation of the biogeographic characteristics of insect faunas of the seven islands in West Coastal of Incheon, Korea, using quantitative analysis. The faunal similarity is examined using the Bray & Curtis similarity. The obtained similarity value matrix was examined by a cluster analysis using UPGMA method. The number and the distribution records of each species in the areas are 1,001 species of insects belonging to 12 orders from the seven investigated islands. Among above seven islands, Seokmodo has the highest number of species, 497 species, while Yeonpyeongdo has the lowest, 136 species. The species composition of insects reported in Ganghwado was 309 species under seven orders. The similarity values between seven localities investigated range from 24.907(Gyodongdo to Yeonpyeongdo) to 49.899(Baengnyeongdo to Ganghwado). That is, the species composition of Baengnyeongdo(47.90%) was similar to that of Ganghwado, while that of Yeonpyeongdo(25.28%) was different from that. The cluster analysis using a similarity index shows that all the islands of these areas can be divided into 3 groups at the level of 30.97%.     

Maintenance and dissemination of avian-origin influenza A virus within the northern Atlantic Flyway of North America

Wild waterbirds, the natural reservoirs for avian influenza viruses, undergo migratory movements each year, connecting breeding and wintering grounds within broad corridors known as flyways. In a continental or global view, the study of virus movements within and across flyways is important to understanding virus diversity, evolution, and movement. From 2015 to 2017, we sampled waterfowl from breeding (Maine) and wintering (Maryland) areas within the Atlantic Flyway (AF) along the east coast of North America to investigate the spatio-temporal trends in persistence and spread of influenza A viruses (IAV). We isolated 109 IAVs from 1,821 cloacal / oropharyngeal samples targeting mallards (Anas platyrhynchos) and American black ducks (Anas rubripes), two species having ecological and conservation importance in the flyway that are also host reservoirs of IAV. Isolates with >99% nucleotide similarity at all gene segments were found between eight pairs of birds in the northern site across years, indicating some degree of stability among genome constellations and the possibility of environmental persistence. No movement of whole genome constellations were identified between the two parts of the flyway, however, virus gene flow between the northern and southern study locations was evident. Examination of banding records indicate direct migratory waterfowl movements between the two locations within an annual season, providing a mechanism for the inferred viral gene flow. Bayesian phylogenetic analyses provided evidence for virus dissemination from other North American wild birds to AF dabbling ducks (Anatinae), shorebirds (Charidriformes), and poultry (Galliformes). Evidence was found for virus dissemination from shorebirds to gulls (Laridae), and dabbling ducks to shorebirds and poultry. The findings from this study contribute to the understanding of IAV ecology in waterfowl within the AF.     

Genetic differentiation in pikeperch (Sander lucioperca): the relative importance of gene flow, drift and common history

To investigate the relative importance of homogenizing factors, such as gene flow, and diversifying factors, such as drift, genetic variation in pikeperch ( Sander lucioperca ) in two Fennoscandian regions (North and South) was analysed with microsatellites. Allelic richness and the degree of differentiation were significantly higher in the North ( F _ST= 0·20) than in the South ( F _ST= 0·064). In northern areas, assignments of genotypes were almost exclusively to the population of origin, but in southern areas, the proportion of correct assignments was significantly lower. Most samples exhibited significant heterozygote deficits, and the level of relatedness was higher than expected from randomness. These combined results suggest that there has been more gene flow between populations in southern areas than in northern areas, where the importance of genetic drift has been greater. Effective population sizes were small ( c. 100) and did not differ between areas. The effect of a common history appears minor, and thus processes such as genetic drift and gene flow have been more influential in shaping the patterns of genetic diversity in this species.     

PHYLOGEOGRAPHY AND WITHIN-STREAM GENETIC VARIATION OF BATRACHOSPERMUM HELMENTOSUM (RHODOPHYTA) USING INTER-SIMPLE SEQUENCE REPEATS

A relatively new molecular marker technique, inter-simple sequence repeats (ISSR), was used to assess the within-stream reach genetic variation and phylogeography of the freshwater red alga, Batrachospermum helmentosum. The within-stream reach study was undertaken in Southeastern Ohio, where 58 individuals were collected from an approximately 200 m stream length. Individuals appeared to be congregated into three distinct areas, with no plants between areas. Using three primers, 100 polymorphic bands were scored. Although it was hypothesized that genetic variation would reflect physical distance, the results showed six distinct genetic groupings, some of which consisted of physically distant individuals. Overall, genetic diversity was greater among individuals than between geographic and genetic groups. To investigate phylogeography, 11 stream reaches (3 from Ohio and one each from Connecticut, Massachusetts, Rhode Island, North Carolina, Tennessee, Indiana, Michigan and Louisiana) were sampled throughout the alga's known distribution in North America. Approximately 15 individuals were collected per stream for ISSR analysis. Five primers, yielding 243 polymorphic bands, were used to examine variation among all individuals. Neighbor-joining trees generated from the Dice, Jaccard and Excoffier coefficients showed that individuals from the same stream formed a clade. Among streams there was no distinct correlation between geographic distance and genetic similarity. Genetic groupings varied slightly among distance coefficients employed. Michigan and Tennessee, Connecticut and Rhode Island, and Indiana and Massachusetts streams consistently showed the same relationship, but the relationships among the three Ohio streams and Louisiana stream were variably related to each other.     

Multivariate hierarchical analyses of Early Jurassic Ostracoda assemblages

Palaeobiogeographic patterns of Early Jurassic ostracods from the northern and southern hemispheres (96 sections located in Europe, North Africa, Western Australia and North and South America) based on 243 species-level records document global patterns of distribution that can be compared to those previously published on ostracods from the European Epicontinental Sea and Tethyan and South Panthalassa areas. All described records of ostracods from both hemispheres spanning the Hettangian to Early Toarcian have been compiled and verified, and their patterns of origin and distribution have been interpreted. Jaccard coefficient of similarity was used to asses similarities among European, American and Tethyan ostracod shelf faunas. The numerical analysis shows a progressive longitudinal gradient in provincialism through the Early Jurassic, consistent with the northward drift of Tethyan ostracod faunas towards the European Epicontinental Sea and the southward movement of European taxa into Tethys and Panthalassa oceans. The spread of cosmopolitan species and extinction of endemic species, allied to the disappearance of geographical barriers, warmer climate conditions and rising sea levels can explain the reduction in ostracod diversity and the east-west provincialism throughout the Early Jurassic. Interchange between hemispheres, including bipolar distributions, are recognized from the Sinemurian time, pointing out that for most of the studied period, the climate worldwide was warm and tropical.     

毛木耳种质资源的RAPD分析

利用22个随机引物对来源不同的56个木耳菌株进行了RAPD分析。结果表明,所有引物的扩增产物DNA片段均表现出明显的多态性,供试菌株总共扩增出164条多态性片段,占总扩增片段的99%;供试菌株两两间的遗传相似系数变化较大(平均GS值0.2143￣0.8764)。采用系统聚类法中的类平均法,对供试的所有菌株两两间相似系数进行聚类,可将它们分为四大类,各大类的类间和类内菌株的遗传变异程度较大,以IV类内各菌株间的最高(平均GS值0.3891),II和III类间的最低(平均GS值0.5887),表明遗传变异也较丰富(总平均GS值0.4918)。将RAPD技术应用于不同菌株间遗传差异的研究,具有反应迅速、不受外界环境条件影响、能从DNA分子水平上揭示菌株间遗传差异等优点,是一种快速准确评估木耳种质资源的有效方法。     

Comparative analysis of alternative statistical models for differentiation of herring stocks based on meristic characters

A basic stock assessment problem is the mixing and separation of herring populations in their specific areas. Within the transition zone between the North and the Baltic seas (Skagerrak, Kattegat, The Sound) a mixing of two herring populations ( Clupea harengus L.) temporarily takes place. One major component stems from the Baltic Sea (spring spawner), and the other from the North Sea (autumn spawner); each stock exhibits different meristic characteristics. In order to separate the two herring populations, 'pure' learning samples of meristic characters were created in 1995 as differential variables. Mainly gained during two research surveys at two geographically remote areas where a mixing of herring components was relatively unlikely, these learning samples were considered as representative for one or the other herring population. This paper compares the current (ICES) separation approach for herring stock assessment with two alternative methods wherein vertebra counts (vc) are used as meristic characters. The two proposed methods are (a) an inverted variance weighted linear model, and (b) a separation rule based on a quadratic discriminant analysis. The paper summarizes and discusses the results of predicting fractions of the two herring components derived from all three separation models. The underlying example data set stems from a 1991–97 routine Swedish survey in the transition zone. In comparison, the quadratic discriminant analysis separation model was identified as superior to the two other methods. Furthermore, the model suggests a higher degree of mixing of the two herring stocks in the transition area than was previously thought; inter-annual changes in the geographical distribution of the two populations are suggested as being less variable than previously assumed.     

INTERCHANGE AND ISOLATION OF HUMPBACK WHALES OFF CALIFORNIA AND OTHER NORTH PACIFIC FEEDING GROUNDS

Humpback whales feed in several high-latitude areas of the North Pacific. We examined the interchange of humpback whales between one of these areas, off California, and those in other feeding grounds in the eastern North Pacific:. Fluke photographs of 597 humpback whales identified off California between 1986 and 1992 were compared with those off Oregon and Washington (29); British Columbia (81); southeastern Alaska (343); Prince William Sound, Alaska (141); Kodiak Island, Alaska (104); Shumagin Islands, Alaska (22); and in the Bering Sea (7). A high degree of interchange, both inter-and intrayear, was found among humpback whales seen off California, Oregon, and Washington., A low rate of interchange was found between British Columbia and California.: two whales seen near the British Columbia/Washington border were photographed off California in a different year, No interchange was found between California and the three feeding areas in Alaska. Humpback whales off California, Oregon, and Washington form a single intermixing feeding aggregation with only limited interchange with areas farther north. These findings are consistent with photographic identification studies in the North Atlantic and with genetic studies in both the North Atlantic and North Pacific.     

Phytogeographical and community similarities of alpine tundras of Changbaishan Summit,China, and Indian Peaks,USA

Abstract. We compared the diversity, phytogeography, and plant communities in two mid-latitude alpine tundras with comparable aerial and elevational extents: Changbaishan Summit in eastern Asia and Indian Peaks in western North America. Despite wide separation, the two areas shared 72 species. In all, 43% of the species on Changbaishan Summit are also distributed in the alpine zones of western North America, while 22% of the species on Indian Peaks are also distributed in the alpine zones of eastern Asia. Almost all the shared species also occur in the Beringian region. Phytogeographical profiles of species and genera showed that 69% of species and over 90% of genera in both alpine tundras belong to the three phytogeographical categories: cosmopolitan, circumpolar, and Asian-North American. We attributed the current floristic relationship between these widely separated areas to the periodic past land connection between the two continents during the Tertiary and Pleistocene. Indian Peaks has a closer floristic relationship with the Arctic tundra than does Changbaishan Summit. Indian Peaks also has 45% higher species richness and lower vegetation cover than Changbaishan Summit. Plant communities from the two areas were completely separated in the two-way indicator species analysis and non-metric multidimensional scaling on floristic data at both species and generic levels, whereas ordination of communities by soil data produced a greater overlap. The plant communities on Changbaishan Summit in general have lower alpha diversity, higher beta diversity (lower between-community floristic similarity), and more rare species than does Indian Peaks. Mosaic diversity does not differ in the two alpine tundras, although the analysis suggests that Changbaishan Summit communities are more widely spaced on gradients than the Indian Peaks communities.     

GEOGRAPHICAL VARIATION IN METRIC SKULL CHARACTERS AMONG PROPOSED SUBPOPULATIONS AND STOCKS OF HARBOR PORPOISE, PHOCOENA PHOCOENA, IN THE WESTERN NORTH ATLANTIC

A total of 433 skulls of harbor porpoises, Phocoena phocoena , were examined to evaluate geographical variation within the western North Atlantic, using analysis of covariance and discriminant analysis based on 45 measurements of skull components. The relationship between condylobasal length and body length was sigmoid in both sexes. Condylobasal length is generally less in adult males than in adult females.
Despite some overlap, morphological differences between different regions and even adjacent local stocks could be recognized by ANCOVA and discriminant analysis. The percentage of correct classification by discriminant functions was 65.2% for the four regional samples: (1) North Canadian Atlantic (which includes Gulf of St. Lawrence and Newfoundland), (2) Bay of Fundy, (3) Gulf of Maine-New York, and (4) Maryland-South Carolina. It was 65.9% for the four local geographical areas (10s of km) within the Bay of Fundy; Quoddy-region porpoises revealed a closer relationship with the southwestern Nova Scotia population than with other adjacent stocks. The results at this level imply that gene flow is restricted to some degree even among closely adjacent geographical units. Management of this species should aim, therefore, for conservation of a variety of local stocks.