摘要:

AbstractGliricidia sepiumprovides a variety of products important for rural communities in tropical countries. Native populations in Meso‐America currently form an important source of seed for distribution to farmers, but concerns centre on mechanisms which may lead to their genetic erosion, including anthropogenic dispersal and subsequent introgression from the related species,G. maculata.Populations ofGliricidiawere examined genetically using approaches based on the polymerase chain reaction to test for interspecific hybridization and introgression betweenG. sepiumandG. maculata. Analysis involved 13 RAPD and two RFLP‐PCR markers which were identified to have species‐diagnostic distributions. Data from both approaches corresponded and indicated three locations where multilocus genotypes were consistent with an hybrid origin. Data at one of these sites was consistent with introgression following hybridization. The hybrid origin of populations was supported by the intermediate geographical location of these sites to ‘pure’ populations of each species. Analysis of maternally inherited organellar DNA, which involved the detection of SSCPs in mitochondrial DNA amplification products, allowed further delineation of genetic structure amongGliricidiapopulations. Mitochondrial data indicated a high degree of organelle differentiation between sampled locations and identifiedG. sepium‐andG. maculata‐diagnostic haplotypes. This data supported the interpretation of genetic structure based on RAPDs and RFLP‐PCR. In addition, cytonuclear analysis allowed the directionality of gene transfer during the formation of hybrid populations to be described. Despite evidence for the occurrence of interspecific hybridization and introgression inGliricidia, important resource populations ofG. sepiumon the Pacific coast appear to have retained their genetic integrity. Implications in terms of the conservation and utilization of genetic resources within the genu

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00294.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe use of RAPDs for comparative purposes relies on the assumption that similarity of fragment size is a dependable indicator of homology. To test the validity of this assumption, homology among 220 pairs of comigrating fragments from three wild sunflower species was determined. Ninety‐one per cent cross‐hybridized and/or displayed congruent restriction fragment profiles suggestive of homology. However, comparative linkage mapping data indicated that 13% of the homologous loci mapped to genomic locations that were incongruent with the majority of loci, suggestive of paralogous rather than orthologous relationships. Thus, of the 220 pairwise comparisons, only 174 (79.1%) identified loci that are useful for comparative genetic studies. These problems, as well as several other factors discussed in the text, will introduce noise into RAPD data sets and thereby reduce the probability of generating accurate estimates of genetic relationships. Recommended methods for reducing noise in RAPD data sets include increasing gel resolution and/or testing fragment homology. However, implementation of these approaches will not eliminate all uncertainties, and it is also recommended that RAPD data sets be tested for structure and reliabil

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00295.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractAs part of a continuing international project to characterize the population genetic (clonal) structure of arctic members of theDaphnia pulexcomplex, 34 populations from western Iceland (N= 1373), and 76 populations from western Greenland (N= 2917), were surveyed for allozymic variation at six polymorphic enzyme loci. Mean clonal richness (±SE) was 1.91±0.19 and 1.50±0.12 for Iceland and Greenland populations, respectively. Mean clonal diversity (±1 SE) was 1.20±0.07 and 1.13±0.04 for Iceland and Greenland populations, respectively. Four widely distributed clones constituted 92.2% of the total animals surveyed from Iceland, while three locally abundant clones constituted 80.1% of the total animals collected primarily from Disko Island, western Greenland. Selected populations were screened for mitochondrial (mt)DNA variation using PCR‐based RFLP analysis of a 2100 bp fragment containing part of the ND4 and ND5 genes. One mtDNA haplotype was very widespread in both western Greenland and western Iceland, although, a number of mutational derivatives were also detected. These data indicate the potential for long‐distance dispersal of mtDNA lineages, of the order of hundreds or thousands of kilometers across the arctic. Phylogenetic analysis of the sequence of a 254 base pair (bp) fragment of the control region of the mtDNA molecule revealed two major clades one of which consisted solely of non‐melanic lineages, and the other of which consisted almost exclusively of melanic lineages (i.e. one non‐melanic lineage also clustered in this clade). Sequence divergence between the two clades averaged 7.3%. Both mitochondrial analyses did not reveal any distinct intraregional clustering of lineages. We discuss our results in reference to previous molecular work done on this arcticDaphniacomplex, and we attempt to infer phylogeographic patterning based on geological/glaciological historical events in this region

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00296.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractA PCR‐based fingerprinting technique based on amplified fragment length polymorphisms (AFLP) is used to screen symbiotic fungi of the fungus‐growing antCyphomyrmex minutusfor genetic differences. AFLP fingerprints reveal several fungal ‘types’ that (a) represent distinct clones propagated vegetatively by the ant, or (b) correspond to free‐living fungi that may be acquired by the ant. Fungal types identified by AFLP fingerprints correspond to vegetative‐compatibility groups established previously, suggesting that vegetative compatibility can be used as a crude indicator of genetic differences between fungi o

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00297.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractIn order to investigate the diversity of fungal endophytes in ericoid mycorrhizal roots, about 150 mycelia were isolated from surface‐sterilized roots of 10 plants ofCalluna vulgaris. Each mycelium was reinoculated toC. vulgarisseedlings under axenic conditions, and the phenotype of the plant‐fungus association assessed by light and electron microscopy. Many isolates that were ablein vitroto produce typical ericoid mycorrhizae did not form reproductive structures under our culture conditions, whereas others could be identified as belonging to the speciesOidiodendron maius. Morphological and molecular analysis of the fungal isolates showed that the root system of a single plant ofC. vulgarisis a complex mosaic of several populations of mycorrhizal and non mycorrhizal fungi. PCR‐RFLP techniques, used to investigate the mycorrhizal endophytes, revealed up to four groups of fungi with different PCR‐RFLP patterns of the ITS ribosomal region from a single plant. Some of the mycorrhizal fungi sharing the same PCR‐RFLP pattern showed high degree of genetic polymorphism when analysed with the more sensitive RAPD technique; this technique may prove a useful tool to trace the spread of individual mycorrhizal mycelia, as it has allowed us to identify isolates with identical RAPD fingerprints on differe

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00298.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractGene transfer within bacterial communities has been recognized as a major contributor in the recent evolution of antibiotic resistance on a global scale. The linkedstrA‐strBgenes, which encode streptomycin‐inactivating enzymes, are distributed worldwide and confer streptomycin resistance in at least 17 genera of gram‐negative bacteria. Nucleotide sequence analyses suggest thatstrA‐strBhave been recently disseminated. In bacterial isolates from humans and animals,strA‐strBare often linked with thesulIIsulfonamide‐resistance gene and are encoded on broad‐host‐range nonconjugative plasmids. In bacterial isolates from plants,strA‐strBare encoded on the Tn3‐type transposon Tn5393 which is generally borne on conjugative plasmids. The wide distribution of thestrA‐strBgenes in the environment suggests that gene transfer events between human, animal, and plant‐associated bacteria have occurred. Although the usage of streptomycin in clinical medicine and animal husbandry has diminished, the persistence ofstrA‐strBin bacterial populations implies that factors other than direct antibiotic selection are involved in m

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00299.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe short‐tailed shearwater is a colonially nesting, socially monogamous seabird. Little is known about mate fidelity and breeding behaviour in this species because breeding birds are nocturnal on land and spend much of their time within subterranean nesting burrows. Colonial breeding and extended sperm storage create opportunities for extra‐pair copulations which may form a significant component of the mating strategy in this species. Multilocus DNA fingerprinting was used to examine the genetic relationship between nestlings and the male and female nest attendants in 83 burrows from two distinct breeding colonies. Genetic analyses identified nine nestlings, approximately equally distributed between the two colonies, that were not related to the attendant pair male in those burrows, implying extra‐pair paternity through extra‐pair copulations. These results are used retrospectively to discuss the characteristics of extra‐pair copulations and extra‐pair fertilizations and the implications for estimates of life‐time reproductive success in the short‐ta

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00300.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractMicrosatellites are one of the most important classes of nuclear genetic markers and offer many advantages for the study of marine mammals. Here we describe the isolation and characterization of 12 cetacean microsatellites which are then tested across 30 different cetacean species. For around half the species tested, five or more polymorphic loci were identified. Since many species were represented by only one or two specimens, this figure is likely to underestimate the usefulness of these markers. No relationship was found between microsatellite repeat length and proportion of species which gave polymorphic products.

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00301.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00302.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00303.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY