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The article documents the occurrence of unusual nonepidemic strains of Vibrio cholerae from Calcutta, India, carrying pilin and cholera toxin genes. Results indicate that the genes are components of the VPI- and CTXphi-type genetic elements, suggesting that the genetic diversity in the virulence-associated gene cluster is evolution related.

The major human sugingival plaque microbial population consists of 347 phenotypes that can be grouped into 9 bacterial phyla based on the 16S rRNA sequence data. Data indicate that the total species diversity in the oral cavity is about 500 species when unidentified and those present on other oral surfaces are considered.

Research discusses differences in population genetic structure of four species of littorinid snails, two with planktonic larval and two with benthic egg mass mode of hatching behavior. Data indicate differences in the genetic structure within the same type of species and development cycle.

Research findings support phylogenetic relationships between morphostatic taxa of the genus Hydrobia s.s. that are distinguishable as species based on cytochrome c oxidase subunit I sequence analysis. Data reveal that each of the populations of Hydrobia sp. A and Hydrobia sp. B are genetically distinct from all other taxa analyzed.

The gene sequence of the oocyst wall protein can be used to differentiate Cryptosporidium species. Substantial diversity of this gene was found in C. wrairi, C. felis, C. meleagridis, C. baileyi, C. andersoni, C. muris, C. serpentis, and C. parvum.

Results show significant allozymic loci frequency differences between flowering dogwood fly and the apple maggot fly with no definite pattern of differences within the individual populations. These data suggest that the flowering dogwood fly can be classified as a separate species.

Research was conducted to examine biodiversity at the genome level in four deep-sea molluscan morphospecies. Haplotype variations in the mitochondrial 16S ribosomal gene of a snail Frigidoalvania brychia and three bivalves, namely Nuculoma similis, Deminucula atacellana and Malletia abyssorum, were studied. Results demonstrate that species diversity may be even higher than estimated by using traditional phenotypic criteria. Some morphologically coherent populations are apparently composed of genetically distinct populations that may represent cryptic species.

DNA sequence analysis is an effective technique for identifying the source of samples that are derived from endangered species. Application of the method and the three-times rule to retail whale meat markets has confirmed the value of mitochondrial and nuclear gene sequences in the conservation of whale populations. Thus, phylogenetic sorting at nuclear loci may produce species-specific sequences when mitochondrial alleles are reciprocally monophyletic and the branches leading to the mitochondrial DNA sequences of a particular whale species are longer than the difference within species.

Patterns of intraspecific genetic differentiation among cetacean populations in parapatry, sympatry and mixed assemblages within a geographic region were investigated. An analysis of examples of resource specialization in vertebrate species showed that the assemblages can be spatially and temporally dynamic, presenting a special problem for conservation managers when cetacean species are hunted on feeding grounds. Intraspecific foraging specializations might play an important role in limiting gene flow between parapatric and sympatric cetacean populations.

Marine organisms pose unique challenges and opportunities for molecular genetic research in conservation biology. Geneticists are showing great interest in conservation issues for marine organisms such as dispersal behavior, demography and population structure. The explosion of interest in conservation genetics can be attributed to the development of usable laboratory methods for the direct assay of DNA and proteins, including the mitochondrial DNA assays for characterizing matrilineages within and among species and direct nucleotide sequencing techniques.

Molecular diversity and population sizes of the mitochondrial 16S rRNA gene were investigated in two species of the North Atlantic planktonic copepods, Nannocalanus minor and Calanus finmarchicus. The objective of the study was to determine whether the two species, which differ in patterns of distribution, abundance and life history, would have different patterns of population genetic diversity and structure in response to climatic changes during the last glacial period. Results showed that both copepods have small effective population sizes and low mitochondrial diversity.

Possible gene flow and introgression within and among three species of rockfishes, namely, Sebastes auriculatus, Sebastes caurinus and Sebastes maliger, were investigated. Nuclear and cytoplasmic evidence were analyzed to determine the geographic variability within each species. Results showed that abrupt changes in allele frequency over relatively short geographic distances occurred in nearshore species when there is no interruption in gene flow or habitat. Changes in gene frequencies of Sebastes maliger were very noticeable.

Spatial and temporal variation in restriction sites of mitochondrial DNA among seven species of marine fishes from the northern Gulf of Mexico and the southeast US Atlantic was investigated. The aim of the study was to find out whether population structure exists in species with an apparent large dispersal potential. Results showed that dispersal and gene flow in three sciaenids follow an isolation-by-distance model. Furthermore, population structuring was nonexistent in the three reef-associated species.

The population genetic structure of widely distributed pelagic marine fishes was investigated. The study focused on four marine fish species with circumtropical populations as well as four species of cosmopolitan temperate fishes with disjunct distributions. Results showed that continuously distributed marine fish species had population structures that are shallow but significant within an ocean basin. In contrast, greater intraspecific genetic divergence was found within discontinuously distributed marine fishes.

Shallow population genetic architectures in deep evolutionary lineages of marine fish species were investigated by reviewing genetic evidence from allozyme and mitochondrial DNA datasets for anchovies and sardines. In addition, factors that influence mitochondrial DNA diversity were examined to gain a better understanding of population regulation in marine fishes. Results showed that regional populations of anchovies and sardines are attenuated by periodic extinctions and recolonizations, apparently resulting in low levels of nucleotide diversity and shallow population histories.

An ancestral sequence of twin microsatellites of rice on separate regions of chromosomes 11 and 12 of has been found in a wild species. The microsatellites had different allele diversities in A genome species of the genus Oryza. The mutation may have been on one of the chromosomes of an ancestor of the A genome species before duplication of the chromosome segments.

The mitochodrial DNA (mtDNA) of several populations of Phonocoena phonocoena harbor porpoises in the Baltic Sea and Norway's joint Kattegat-Skakegerrak Seas were analyzed to determine their genetic identities. Analysis of the restriction fragments of mtDNA from eastern North Atlantic populations of harbor porpoises indicated the presence of five new restriction patterns and seven new haplotypes. However, subpopulations of North Atlantic harbor porpoises exhibited low genetic diversity.

The presence of allozyme and mitochondrial DNA variants was investigated in subpopulations of southern bluefin tuna from South Africa, Tasmania, Western and Southern Australia to determine their genetic diversity. Genetic screening of subpopulations of Thunnus maccoyii indicated the absence of statistically significant genetic differentiation. Furthermore, there was no evidence of selection mechanisms that operate to change gene or mitochondrial DNA haplotype frequencies in response to aging in fish populations.

Cloning and sequencing of two DNA polymerase chain reaction products having different sizes reveal that they possess the same DNA sequence barring a stretch of tandem repeats (microsatellite) of AAG.TTC. The microsatellites differ in size. This method of identifying microsatellite loci in fungal genome can be used to determine the genotypic and ecological diversity of fungi. The frequency of microsatellite loci in fungal genome is an indication of the potential of the genetic marker approach to fungal diversity studies.

Genetic variation among wheat (Triticum aestivum L.) parents is necessary to derive superior progeny from crossing and selection. However, crosses are often performed among elite lines with similar agronomic and end-use characteristics. Thus, the potential exists for an undesirable narrowing of the germplasm base for any particular class of wheat. The relative genetic diversity within hard red spring wheat was determined in comparison to a sample of wheat accessions representing an array of types and geographic origins. Three groups of accessions were assayed for the frequencies of DNA polymorphism using a total of 38 sequence-tagged-site primer sets with polymerase chain reaction. Group I contained 10 elite hard red spring wheat cultivars under production in Montana and North Dakota, Group II included 15 hard red spring wheat cultivars and lines from the North American Great Plains, and Group III contained 20 accessions representing a wide range of collection and morphological types. Twenty-four of 38 primer sets (63%) and 31 of 76 primer-enzyme combinations (41%) revealed polymorphisms. The range of genetic similarity estimated by percentage of shared restriction fragments varied from 0.65 to 0.99 among all pairwise comparisons among the 45 lines. Average genetic similarity was 0.81. Genetic similarity among the hard red spring wheats was 0.88, whereas genetic similarity among the broadly based Group III was 0.78. Our results showed that the breeding pool for hexaploid hard red spring wheat is narrow relative to levels of diversity among and within classes in hexaploid wheat.

The reported genetic diversity of North American soybean [Glycine max (L.) Merr.] cultivars is low. Public and industry breeders have initiated programs to expand the diversity. This paper assesses the impact of diversification efforts on the extent and pattern of diversity among elite lines and estimates the impact of industry on diversity. Coefficient of parentage (CP) analyses were performed with 122 lines from the northern and southern regions of the USA. The average CP was 0.173: this value was 0.233 among northern lines, 0.261 among southern lines, and 0.100 between lines from different regions. These values, and an analysis of the number of ancestors and their contribution of parentage to the elite population, were similar to values in previous reports, thereby indicating that recent efforts of public and proprietary breeders have had little impact on diversity among current elite lines. Minor differences in genetic diversity were noted between lines from public or proprietary sources. Industry has affected diversity by introducing parentage from PI 257.435, and the development of 'A3127' has served as a genetic bridge between regions. Cluster analysis distinctly separated northern lines from Maturity Group V and VI lines and suggested four clusters within each region. Principal component analyses interpreted the clusters as groups of lines with genetic similarity to recently developed parents that were used extensively to generate the elite population. Genetic diversity within and between regions could be exploited by crossing pairs of lines that have a low CP. The effectiveness of this approach could be enhanced by using cluster patterns to achieve a more thorough sampling of the genetic diversity.

The central part of the mitochondrial coxII gene was amplified from 38 different dicots and two monocots using polymerase chain reaction. In 30 of the 40 plants studied, the amplified coxII gene-fragment contains an intron, ranging from 930 bp in Capsicum (pepper) in Solanaceae to 1,635 bp in Ampelamus albidans (climbing milkweed) in Asclepiadaceae. The composition of this intron varies as revealed by Southern hybridizations using oligonucleotide probes specific to the coxII intron-regions in maize, wheat, and rice. In the Apocynaceae, Catharanthus roseus (Madagascar periwinkle) and Vinca minor (common periwinkle) lack the coxII intron, while other members of the same family (various Mandevilla species, Nerium oleander and Apocynum cannabinum) and members of the closely related Asclepiadaceae (Asclepias incarnata, Ampelamus albidans and Asclepias tuberosa) retain the intron. Analysis of these data suggest a selective loss of the coxII intron from a plant, ancestral to both Catharanthus and Vinca, after the divergence of the Asclepiadaceae and Apocynaceae. The remaining eight plants from the Brassicaceae, Cucurbitaceae, Fabaceae, and Onagraceae lacking the intron fall into a single group or clade using the phylogenetic tree proposed by Chase et al. (Annals of the Missouri Botanical Garden: 80: 528-580, 1993) based on sequence of the chloroplast rbcL gene.

Enzyme electrophoresis was employed to assess genetic diversity within and divergence among four species of Robinsonia (R. evenia, R. gayana, R. gracilis, R. thurifera), a genus endemic to the Juan Fernandez Islands, Chile. The genus consists of treelike perennial plants, and all species are dioecious. Morphological diversity within the genus is reflected by recognition of two subgenera, with three sections in one subgenus. Total gene diversity is highest in the two species (R. gayana and R. gracilis) that are most common and have the largest population sizes. Robinsonia evenia has only half and the rare R. thurifera only 20% of the diversity detected in the other two species. The diversity measured in R. gayana and R. gracilis is comparable to the values typical of continental species of flowering plants with similar life history attributes. The genetic identities between species range from 0.560 to 0.706, which is similar to or below many values for congeneric species, but much lower than most reports for congeners on oceanic islands. The higher diversity within and divergence among species of Robinsonia compared to many insular endemics may result from several factors. The genus probably arose from self-incompatible plants of the genus Senecio, which means that several to perhaps many colonizers carried considerable allozymic variation to the Islands. Large population sizes and obligate outcrossing are additional factors that would account for higher diversity. Sorting of alleles during radiation and the process of mutation probably combined to produce divergence among the species. Estimated divergence times calculated for the species from allozyme data range from 1.7 to 5.5 million years depending on the assumptions made in the calculations; the age of the island (Masatierra) on which these four species are confined is approximately 4.0 million years. The electrophoretic data suggest that Robinsonia arrived early in the archipelago, and radiated and speciated rapidly after colonization.

MtDNAs from 2 protein coding regions comprising 576 base pairs were sequenced from 17 individual sea urchins of the species Stronglocentrotus pallidus collected from the north Pacific and north Atlantic oceans. Twelve of 17 individual sequences were identical. Two of these were further sequenced in a third, 441 base pair region, and were also found to be identical. We show how to interpret these results using a simplified Markov model of mtDNA evolution at silent sites. The model was calibrated using 3 urchin species with a published fossil record, and shows that identical S. pallidus mtDNAs in different oceans shared a common ancestor at most 90,000-150,000 years ago (95% confidence interval of upper limit of divergence). The Markov model, used to examine patterns of genetic distance within and between species, shows unexpected variation in the rate of base substition. The rate of change of G's at fourfold sites in nearly 20 times greater than the rate of change of C's. At twofold sites, this range is less extreme, although purines consistently have a higher rate of change than pyrimidines. Striking genetic similarity and recent genetic exchange between oceans for these urchins is in marked contrast to to most other trans-Arctic marine populations, which usually show morphological and genetic differentiation at the species or subspecies level. Recent fossil evidence shows that the north Atlantic and northeastern Pacific have been the scene of radical faunal changes during the Pliocene and Pleistocene. The genetic results presented here extend this conclusion to intraspecific patterns of genetic variability, and direct attention to the northwest Pacific where higher productivity and less environmental change may have left a heritage of greater marine genetic diversity. Diversity, genetic exchange, Markov model, mtDNA, population biology, Strongylocentrotus pallidus, trans-Arctic populations.

Lathyrus latifolius (everlasting pea) is a perennial vine native to Europe. Naturalized populations of L. latifolius occur in fields and on roadsides over large areas of the United States. Widely cultivated as a garden flower, L. latifolius produces abundant racemes of showy flowers that are bumblebee-pollinated. The seeds areheavy, large, and round, and exhibit no specialized means of dispersal. Allozyme diversity and population structure were determined for 32 populations of L. latifolius -- 30 from the southeastern United States and two from Oregon. Results from 21 allozyme loci indicate that genetic diversity is higher and population divergence is lower than expected based on the life history characteristics of the species. No association was found between genetic identity statistics and geographic distance between populations. Although the range in genetic diversity statistics among populations was unusually large, genetic drift did not appear to play a major role in structuring genetic variation. We conclude that the level of genetic diversity maintained within L. latifolius populations, and the level of population divergence found, is strongly influenced by its status as a cultivated garden flower and its human-associated mode of gene flow via seed dispersal.

This study surveys genetic variation in two clonal, monoecious, water-pollinated species that differ in their extent of sexuality and distributional range. Electrophoresis was used to quantify allozyme variability in 12 Wisconsin populations of the widespread Ceratophyllum demersum and the rare C. echinatum. Electrophoretic data indicate that populations of both species have low levels of sexual recombination, low levels of variation, and are structured genetically like inbreeding terrestrial plants. Ceratophyllum populations differ from 'typical' clonal terrestrial plants by lower genetic diversity, lower proportions of multiclonal populations, and fewer genotypes per population. In two populations where sexual recombination is documented, heterozygosit is low with significant deficiencies. Monoecy in Ceratophyllum may be related to historical evolutionary factors, whereas vegetative reproduction has a greater influence on the genetic population structure of extant populations. The low genetic identity between C. demersum and C. echinatum support their recognition as distinct species.

This study describes levels of allozyme diversity and patterns of genetic structure within and among populations of honey locust (Gleditsia triacanthos L.). Using data from starch gel electrophoresis, honey locust was found to have high genetic diversity within populations ([H.sub.E] = 0.198), and low, but significant genetic differentiation among populations ([G.sub.ST] = 0.059). Temporal and spatial substructuring were also investigated in two populations from eastern Kansas. Few genetic differences were found among nine age classes in one population and between juveniles and adults in the second population. Separate autocorrelation analyses of juveniles and adults revealed significant spatial substructuring in both age classes. Three conclusions were reached from these analyses. First, even small amounts of clonal growth can cause large increases in the amount of substructuring in populations. Second, spatial genetic substructuring among juveniles at both sites most likely represents the presence of family groups. Last, the overall level of spatial genetic substructuring at both sites was somewhat greater in the juvenile classes than in the nonclonal adult classes. This latter conclusion is consistent with theoretical studies suggesting that limited gene movement causes a steady increase in spatial structure from generation to generation.

Genic analyses of cytotypes of Peromyscus truei and p.difficilis were conducted to determine the magnitude to genic evolution that has accompanied chromosomal divergence. Two species currently assigned to the boylii group were included. The distinctness of northern and southern cytotypes of P.truie was documented and supports other investigators who concluded than the southern cytotype should be elevated to specific status. Cytotypes of P.difficilis were not genically distinct at 28 presumptive loci and do not appear to represent separate species. P.attwateri, currently placed in the boylii group, is related closely to P.difficilis. P.difficilis is the sister taxon of P.gratus.

Patterns of variation at 13 isozyme loci were examined in 11 populations in three Cistus species strictly endemic to the Canary Islands. Cistus osbaeckiaefolius and C. chinamadensis display low levels of isozyme variation associated with moderate to high interpopulation differentiation, which probably arose through historical bottlenecks in a landscape of habitat fragmentation, grazing, and human influence. By contrast, C. symphytifolius ranks among the subset of narrow endemics with high levels of isozyme variation and features different degrees of genetic structuring that are closely associated with taxonomic ascription. Low interpopulation differentiation in var. leucophyllus is possibly a reflection of its recent origin or of moderate levels of gene flow between its populations. High interpopulation differentiation in var. symphytifolius probably arose due to slight ecological differences between populations coupled with low levels of gene flow. Interpretation of neighbor-joining trees in the light of geological data substantiates the hypothesis that C. symphytifolius (or a very close relative) might be the ancestor of the other stands of Cistus in the islands. Conservation implications of our survey are the identification of the two populations of C. chinamadensis with the highest allele and genotype richness for preservation on genetic grounds and advice to prevent artificial gene flow in this taxon lest it might disrupt locally adapted gene combinations. All populations of C. osbaeckiaefolius should be given conservation priority on ecological grounds despite their genetic depauperation. Key words: allozymes; Canary Islands; Cistaceae; Cistus; conservation genetics; genetic differentiation; genetic variability.

Rapid divergence in postmating-prezygotic characters suggests that selection may be responsible for generating reproductive barriers between closely related species. Theoretical models indicate that this rapid divergence could be generated by a series of male adaptations and female counteradaptations by means of sexual selection or conflict, but empirical tests of particular mechanisms are generally lacking. Moreover, although a male-female genotypic interaction in mediating sperm competition attests to an active role of females, molecular or morphological evidence of the female's participation in the coevolutionary process is critically needed. Here we show that postmating-prezygotic variation among populations of cactophilic desert Drosophila reflects divergent coevolutionary trajectories between the sexes. We explicitly test the female's role in intersexual interactions by quantifying differences in a specific postmating-prezygotic reproductive character, the insemination reaction mass, in two species, Drosophila mojavensis and Drosophila arizonae. A series of interpopulation crosses confirmed that population divergence was propelled by male-female interactions, a prerequisite if the selective forces derive from sexual conflicts. An association between the reaction mass and remating and oviposition behavior argues that divergence has been propelled by sexually antagonistic coevolution, and potentially has important implications for speciation.

Developmental Evolution (DE) contributes to various research programs in biology, such as the assessment of homology and the determination of the genetic architecture underlying species differences. The most distinctive contribution offered by DE to evolutionary biology, however, is the elucidation of the role of developmental mechanisms in the origin of evolutionary innovations. To date, explanations of evolutionary innovations have remained beyond the reach of classical evolutionary genetics, because such explanations require detailed information on the function of genes and the emergent developmental dynamics of their interactions with other genetic factors. We argue that this area has the potential to become the core of DE's disciplinary identity. The main challenge in developing a research program for DE along these lines, however, is to provide a methodological framework that accounts for the fact that developmental mechanisms continue to evolve after a character has originated. Developmental mechanisms elucidated in a derived species may therefore not provide insights into the evolutionary origin of the character in question. To meet this challenge, we propose a set of questions that may guide us in our search for valid inferences on the role of developmental mechanisms in the explanation of evolutionary innovations.

Taraxacum officinale complex was introduced from Europe into Korea about a hundred years ago. This species widely occurs on Korean penninsula and take over the habitats of native species of Taraxacum and increasingly common in open habitats. Taraxacum officinale complex produce more aboundant apomictic seeds than native species, however, some populations also show facultative sexual reproduction. Native species consist of diploid, triploid, and tetraploid and show a series of facultative sexual reproduction. In order to measure the degree of gene flow between native and introduced species, we analyzed the maternally inherited chloroplast DNA markers and biparentally inherited nuclear DNA markers from 130 populations of Taraxacum. Nuclear ITS tree show the morphologically circumscribed species boundaries both in native and introduced species. However, cpDNA trees was substantially different from that of nuclear rDNA and show mixed patterns between European and Asian species. The results suggest that the introgressive hybridizations are relatively common between native and introduced species of Taraxacum. The unidirectional intrgression from introduced species into native species is one of major driving force to extiction of native populations. Hybridizations are relatively rare among native species because of disjunctive distribution.

Cytogenetic relationships among three races of pocket gophers (Geomys bursarius complex) at two hybrid zones in eastern Texas were examined by use of chromosome-banding and meiotic analyses. Race E (2n = 74, FN = 72) interacts with races F (2n = 70, FN = 74) and G (2n = 70, FN = 72) at a narrow (0.8 km) hybrid zone in Burleson Co., Texas. Of 78 pocket gophers collected there, three (3.8%) were [F.sub.1] hybrids and none was a backross or [F.sub.2] hybrid. Races f and G contacted one another at a second hybrid zone 35 km in width, located in Milam and Burleson counties, Texas. Backcross and [F.sub.2] hybrids between races F G could not be distinguished chromosomally from [F.sub.1] hybrids, but distribution patterns of parental and hybrid pocket gophers suggest that hybrids included backcross or [F.sub.2] animals. G-band chromosome analysis revealed that races F and G differ from race E by at least two centric fission-fusion events. Further chromosomal rearrangements distinguishing race E from the other two races were indicated by G-bands, but could not be identified specifically. C-banded karyotypes revealed heterochromatic differences between race E and races F and G. Races F and G differed in one whole-arm heterochromatic change, as evidenced by C-banding, and by a paracentric inversion, demonstrated by G-banding. Chromosomal distinctions among the races were supported by meiotic analyses of hybrids. Degree of hybridization among the three races and the width of the hybrid zones reflect the extent of cytogenetic divergence of the races. The narrow zone between the 2n = 74 form and the 2n = 70 forms is most likely the result of meiotic imbalances and associated decreases in viability from a minimum of two and probably more rearrangements. The broad zone of hybridization between the two 2n = 70 forms is characterized by much higher hybrid production. The identified rearrangements in the karyotypes of races F and G and their hybrids have not resulted in the degree of reduced fitness evident in hybrids involving race E. Races F and G, and race E interact as species, recognized as Geomys attwateri and G. breviceps, respectively.

Genotypic diversity is restricted within local colonies of mayapple (Podophyllum peltatum), due to extensive asexual reproduction. Transplant experiments were used to examine whether disease impact from a specialist fungal pathogen (Puccinia podophylli) was affected by the local frequency of host genotypes within colonies. In each of six large mayapple colonies, I measured infection intensity on 1) ramets replanted in their native colony (which were thus surrounded mostly by identical genotypes) and 2) transplants from two foreign colonies (surrounded by different genotypes). Disease incidence during the pathogen's first generation did not vary significantly between native (11% infected) and foreign host genotypes (6% infected). In the pathogen's second generation, significant variation in infection intensity occurred among ramets from different source populations. However, at five of the six transplant sites, mean infection intensity was higher on some nonnative plants (locally rare host genotypes) than on natives (locally common host genotypes). In this system, pathogen attack does not act in a frequency-dependent manner to promote local genetic diversity among hosts.