摘要:

AbstractBuffalograss,Buchloë dactyloides, is widely distributed throughout the Great Plains of North America, where it is an important species for rangeland forage and soil conservation. The species consists of two widespread polyploid races, with narrowly endemic diploid populations known from two regions: central Mexico and Gulf Coast Texas. We describe and compare the patterns of allozyme and RAPD variation in the two diploid races, using a set of 48 individuals from Texas and Mexico (four population samples of 12 individuals each). Twelve of 22 allozyme loci were polymorphic, exhibiting 35 alleles, while seven 10‐mer RAPD primers revealed 98 polymorphic bands. Strong regional differences were detected in the extent of allozyme polymorphism: Mexican populations exhibited more internal gene diversity (He= 0.20, 0.19) than did the Texan populations (He= 0.08, 0.06), although the number of RAPD bands in Texas (n= 62) was only marginally smaller than in Mexico (n= 68).F‐statistics for the allozyme data, averaged over loci, revealed strong regional differentiation (meanFRT=+ 0.30), as well as some differentiation among populations within regions (meanFPR=+ 0.09). In order to describe and compare the partitioning of genetic variation for multiple allozyme and RAPD loci, we performed an Analysis of Molecular Variance (AMOVA). AMOVA for both allozyme and RAPD data revealed similar qualitative patterns: large regional differences and smaller (but significant) population differences within regions. RAPDs revealed greater variation among regions (58.4% of total variance) than allozymes (45.2%), but less variation among individuals within populations (31.9% for RAPDs vs. 45.2% for allozymes); the proportion of genetic variance among populations within regions was similar (9.7% for RAPDs vs. 9.6% for allozymes). Despite this large‐scale concordance of allozyme and RAPD variation patterns, multiple correlation Mantel techniques revealed that the correlations were low on an individual by individual basis. Our findings of strong regional differences among the diploid races will facilitate further study of polyploid evolution in buffal

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00203.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractCyclic parthenogenesis is the ancestral mode of reproduction in the cladoceran crustacean,Daphnia pulex, but some populations have made the transition to obligate parthenogenesis and this is the only mode of reproduction known to occur in arctic populations. Melanism and polyploidy are also common in arctic populations of this species. Prior allozyme studies of arcticD. pulexrevealed substantial levels of clonal diversity on a regional scale. Clonal groupings based on cluster analysis of allozyme genotypes do not conform to groupings based on the presence/absence of melanin or on ploidy level. In order to further elucidate genetic relationships among arcticD. pulexclones, mitochondrial DNA (mtDNA) variation was examined in 31 populations from two Canadian high‐arctic sites. The data were also compared to a previous study of mtDNA variation in populations from a Canadian low‐arctic site. Cladistic analysis of restriction site variation of the entire mitochondrial genome and nucleotide sequence variation of the mitochondrial control region was used to construct genetic relationships among mitochondrial genotypes. Three distinct mitochondrial lineages were detected. One lineage was associated with diploid, nonmelanic clones and is the same as the lineage that is found in temperate populations ofD. pulex.The other two lineages (A&B) were associated with polyploid, melanic clones. Sequence divergence between the A and B lineages was 2.4%. Sequence divergence betweenD. pulexand either of these two lineages exceeded 3%. It is suggested that the melanic, polyploid clones are hybrids between males ofD. pulex(and/or a closely related congener,D. pulicaria) and females of either of two ancestral melanic species that have mitochondrial lineages A and B. Geographic patterns of mitochondrial diversity in ‘melanic’ lineage B support the hypothesis of an high‐arctic refuge for the ancestral species during the last glaci

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00204.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractWe employed restriction site variation in mitochondrial (mt)DNA to determine if significant phylogeographic structure occurs in the North American cyprinid fishCyprinella lutrensis. Digestion patterns from 16 restriction endonucleases identified fifty mtDNA haplotypes among 127 individuals ofCyprinella lutrensisassayed from localities in the Gulf Coastal Plain, the Great Plains, and the Central Lowlands. Nucleotide sequence divergence among haplotypes was highly variable (mean ± SE: 2.87%± 0.08; range: 0.14–9.24%). Maximum‐parsimony analysis and the neighbour joining method of tree construction revealed three major groupings (clades) of haplotypes that differed in geographic distribution. Divergence estimates between the basal clade, comprised of haplotypes primarily from the Brazos River in east Texas, and the remaining two clades, place C.lutrensisin the western Gulf Coastal Plain prior to Pleistocene glaciation. Nucleotide sequence divergence between the second clade, comprised of haplotypes from the Trinity and Calcasieu rivers in east Texas and southwestern Louisiana, respectively, and the third clade (comprised primarily of haplotypes from localities north of Texas and affected directly by Pleistocene glaciation), suggest thatC. lutrensiscolonized gladated regions to the north during the mid‐ to late Pleistocene. This hypothesis is supported by levels of intrapopulational nucleotide diversity in geographic localities outside of Texas and by geological evidence. Despite marked geographic variation in morphometries, meristics, and nuptial coloration, mtDNA variation in glaciated regions was not geographically structured, and subspecies ofC. lutrensiswere not identifiable by phylogenetic analysis o

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00205.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe cyprinid fishesLuxilus cornutusandLuxilus chrysocephalushybridize extensively in a zone extending through the Great Lakes region with extensive introgression ofL. cornutusmtDNA occurring in populations ofL. chrysocephalussouth of the present hybrid zone in Ohio. Western populations of these two species occur adjacent to one another in Missouri but hybridization has never been observed. In order to determine if hybridization has occurred historically in Missouri, allopatric populations ofL. chrysocephaluswere analysed for mtDNA introgression. Extensive introgression ofL. ***cornutusmtDNA was observed in most populations ofL. chrysocephalusin Missouri resulting in the elimination ofL. chrysocephalusmtDNA in many populations.Luxilus cornutusmtDNA inL. chrysocephalusis found approximately 300 km south of extantL. cornutuspopulations in Missouri.Luxilus chrysocephalusmtDNA was replaced by four uniqueL. cornutusmtDNA haplotypes, with one particular haplotype becoming fixed in severalL. chrysocephaluspopulations. The pattern of introgression suggests that historicallyL. cornutusoccupied a more southern distribution in Missouri bringing it into contact with western populations ofL. chrysocephalusand resulting in a hybrid zone.

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00206.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractInsertion sequence (IS) hybridization was used to define the structure of a population ofRhizobium melilotiisolated directly from soil and from nodules ofMedicago sativa(alfalfa) andMelilotus alba(sweet clover) grown under controlled conditions and inoculated with a suspension of the same soil. The detection ofR. melilotiisolated from soil on agar plates was facilitated by use of a highly species specific DNA probe derived from ISRm5. All R.melilotiobtained directly from soil proved to be symbiotic (i.e. nodulated and fixed nitrogen with alfalfa). Analysis of 293R. melilotiisolates revealed a total of 17 distinct IS genotypes of which 9, 9 and 15 were from soil,M. albaandM. sativa, respectively; 8 genotypes were common to soil and both plant species. The frequency ofR. melilotigenotypes from soil differed markedly from that sampled from nodules of both legume species: 5 genotypes represented about 90% of the isolates from soil whereas a single genotype predominated among isolates from nodules accounting for more than 55% of the total. The distribution of genotypes differed betweenM. sativaandM. albaindicating species variation in nodulation preferences for indigenousR. meliloti. The data are discussed in the context of competition for nodulation of the host plant and the selection ofRhizobiumstrains for use in legume inoculants. This study has ecological implications and suggests that the composition ofR. melilotipopulations sampled by the traditionally used host legume may not be representative of that actually present in soil.

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00207.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractDeclines in the number of anadromous brown trout in the Karup River in Denmark, due to environmental degradation, led to the stocking of large numbers of hatchery trout during the 1980s. This practice was gradually replaced by stocking with the offspring of electrofished local trout The genetic contribution of the hatchery fish to the current population of anadromous trout in the river was estimated by restriction fragment length polymorphism analysis of mitochondrial DNA, using seven restriction endonucleases. Fish from the hatchery strain as well as from five locations in the river system, and from a further unstocked river were screened. Eight haplotypes were observed. The distribution and frequencies of the observed haplotypes revealed little genetic differentiation among stocked populations. The hatchery strain differed significantly from the stocked populations. One haplotype which was found at a high frequency in the hatchery strain was almost absent from the stocked populations. This suggests that the genetic contribution of the hatchery trout to the current population is much less than would be expected from the number of stocked fish. The possible reasons for the failure of the hatchery trout to contribute to the gene pool, and also the implications for conservation biology, are discussed.

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00208.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA survey of allozyme diversity within and between populations ofSilene acaulisfrom Spitsbergen, Norway, Iceland and Scotland, showed that populations from the high Arctic (Spitsbergen,>76°N) contained high levels of diversity and were genetically similar to populations from more southern locations. Indirect measures of gene flow (Nm), calculated from Wrigh's F indicated that there had been extensive gene flow between Spitsbergen and some Norwegian populations. A restriction site analysis of chloroplast DNA (cpDNA) inS. acaulisrevealed that all populations contained a single identical cpDNA haplotype, except one population from Norway which also contained a second haplotype. In contrast, five different cpDNA haplotypes were distinguished in a more limited survey of cpDNA variation inSaxifraga oppositifolia, with all five haplotypes present in one of two Spitsbergen populations surveyed. The contrasting cpDNA results for the two species suggest that whereas high‐Arctic populations ofSilene acaulishave most likely been derived from immigrants which arrived from the south after the last glacial period, high‐Arctic populations ofSaxifraga oppositifoliamay be derived, in part, from ancient northern stocks which survived the last glaciation in high‐Arctic r

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00209.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA collection of 121 isolates ofRhizobium leguminosarumbiovar (bv.)trifoliiwas obtained from root nodules ofTrifolium subterraneumL. (subclover) plants growing in an established pasture. The collection consisted of a single isolate from each of 18 plants sampled from seven microplots. The following year, a further 28 and 27 isolates were collected from the first and seventh sampling points, respectively. Analysis of restriction fragment length polymorphisms (RFLPs) of both chromosomal and Sym (symbiotic) plasmid DNA and multilocus enzyme electrophoresis (MLEE) were used to assess the diversity, genetic relationships and structure of this population. Symbiotic effectiveness tests were used to examine the symbiotic phenotype of each isolate collected in the first year. Analysis of RFLPs of the first year isolates revealed 13 chromosomal types and 25 Sym plasmid types. Similar Sym plasmid types were grouped into 14 families containing 1–6 members. No new chromosomal types and six new Sym plasmid types were detected in the second year. The symbiotic effectiveness of the first year isolates of the same Sym plasmid type was similar. Significant differences in symbiotic effectiveness were detected between different Sym plasmid types in the same plasmid family. Representative isolates of each chromosomal type Sym plasmid type identified in the first year were analysed using multilocus enzyme electrophoresis. Mean genetic diversity per locus was high (0.559). Enzyme electrophoresis revealed 17 electrophoretic types (ETs). Ouster analysis of the enzyme data revealed large genetic diversity amongst the ETs. Strong linkage disequilibrium was observed for the population as a whole, i.e. clonal population structure, but significantly less disequilibrium was observed among a cluster of ETs suggesting that recombination occurred between ETs within the cluster. Our results revealed that a population of naturally occurring isolates ofRhizobium leguminosarumbv.trifoliican be genetically diverse and support the possibility that recombination plays a role in generating new genotype

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00210.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of a genetically engineeredPseudomonas aureofaciens(Ps3732RNL11) strain (GEM) and the parental wild‐type (Ps3732RN) on decomposition of cellulose paper, straw and calico cloth was assessed after 18 weeks incubation in laboratory soil microcosms. Effect(s) of inoculum density (103, 105, and 108cells/ g dry soil) and single versus multiple bacterial inoculations were also investigated. Cellulose paper was completely decomposed after 18 weeks in all treatments. There were no significant differences (95% level), between treatments, in percentage decomposition of either straw or calico cloth. Recovery of the GEM at 18 weeks, using viable plating, was limited to treatments originally receiving 108cells/g dry soil. Log 1.8 CFU/g dry soil were recovered from the single dose treatment while log 4.2 CFU/g dry soil were recovered from the multiple dose treatment Biolog metabolic tests were used to determine if the GEM or parental wild‐type had any effect on overall carbon utilization in soil. Results suggested they did not. Detection of the recombinantlacZY gene sequence in soil using PCR suggested the possibility of viable but nonculturable cells and/or persistence of chromosomal

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00211.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractTo gain a deeper understanding of the mechanisms underlying associations between allozyme genotypes and rates of respiration inLolium perenne, VmaxKmand rates of glucose flux through glycolysis and the pentose phosphate pathway were estimated for the three genotypes of the6pgdlocus. KmVmaxand Vmax/Kmdiffered significantly among genotypes. Values of Kmfor the 11, 12, and 22 genotypes were 0.29, 0.25, 0.13, while the values of Vmax/Kmfor die 11, 12, and 22 genotypes were 3.79, 3.85, 6.70. Flux through the pentose shunt did not differ among genotypes at 20 °C, but at 35 °C the rates of flux for the 11, 12, and 22 genotypes were 0.15, 0.25 and 0.42, respectively. Thus, the 6PGD allozyme genotypes differ markedly in both enzyme kinetic characteristics and in flux through a metabolic pathway. These associations reveal potentially causal relationships between allozyme genotypes and rates of respiratio

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00212.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY