ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00284.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.tb00285.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe Swedish moose was analysed for genetic variability at major histocompatibility complex (MHC) class I and class IIDQA, DQBandDRBloci using restriction fragment length polymorphism (RFLP) and single strand conformation polymorphism (SSCP) techniques. Both methods revealed limited amounts of polymorphism. Since the SSCP analysis concerned an expressedDRBgene it can be concluded that the level of functional MHC class II polymorphism, at least at theDRBlocus, is low in Swedish moose. DNA fingerprinting was used to determine if the unusual pattern of low MHC variability could be explained by a low degree of genome‐wide genetic diversity. Hybridizations with two minisatellite probes gave similarity indices somewhat higher than the average for other natural population, but the data suggest that the low MHC variability cannot be explained by a recent population bottleneck. However, since minisatellite sequences evolve more rapidly than MHC sequences, the low levels of MHC diversity may be attributed to a bottleneck of more ancient origin. The selection pressure for MHC variability in moose may also be reduced and we discuss the possibility that its solitary life style may reduce lateral transmission of pathogens in the populatio

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00286.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractOver 10000Glossina pallidipestsetse flies were collected during two field studies in the Zambezi Valley, Zimbabwe and one in the Luangwa Valley, Zambia. These were screened for mature trypanosome infections and 234 dot‐blot preparations were made of infected midguts, which were screened using DNA probes or PCR with primers specific to different species or types of the trypanosome subgenusNannomonas. Over 70% of midgut infections were successfully identified as eitherTrypanosoma godfreyi, T. simiaeor three types ofT. congolense, savannah, riverine‐forest and Kilifi. The relative abundance of species and types did not vary significantly between study locations, habitat, season or tsetse age or sex, although there were differences between DNA probe and PCR results. Mixed species and/or mixed type infections were common and were more often detected using PCR. The distribution of infections among flies was highly aggregated, but there was no tendency for multiple infections to accumulate in older flies, implying that sequential superinfection may be uncommon. Possible explanations for these patterns are discus

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00287.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractTen microsatellite loci and a partial sequence of the COII mitochondrial gene were used to investigate genetic differentiation inB. terrestris, a bumble bee of interest for its high‐value crop pollination. The analysis included eight populations from the European continent, five from Mediterranean islands (six subspecies altogether) and one from Tenerife (initially described as a colour form ofB. terrestrisbut recently considered as a separate species,B. canariensis). Eight of the 10 microsatellite loci displayed high levels of polymorphism in most populations. InB. terrestrispopulations, the total number of alleles detected per polymorphic locus ranged from 3 to 16, with observed allelic diversity from 3.8 ± 0.5 to 6.5 ± 1.4 and average calculated heterozygosities from 0.41 ± 0.09 to 0.65 ± 0.07.B. canariensisshowed a significantly lower average calculated heterozygosity (0.12 ± 0.08) and observed allelic diversity (1.5 ± 0.04) as compared to both continental and island populations ofB. terrestris. No significant differentiation was found among populations ofB. terrestrisfrom the European continent. In contrast, island populations were all significantly and most of them strongly differentiated from continental populations.B. terrestrismitochondrial DNA is characterized by a low nucleotide diversity: 0.18%± 0.07%, 0.20%± 0.04% and 0.27%± 0.04% for the continental populations, the island populations and all populations together, respectively. The only haplotype found in the Tenerife population differs by a single nucleotide substitution from the most common continental haplotype ofB. terrestris. This situation, identical to that of Tyrrhenian islands populations and quite different from that ofB. lucorum(15 substitutions betweenterrestrisandlucorummtDNA) casts doubts on the species status ofB. canariensis. The large genetic distance between the Tenerife andB. terrestrispopulations estimated from microsatellite data result, most probably, from a severe bottleneck in the Canary island population. Microsatellite and mitochondrial DNA data call for the protection of the island populations ofB. terrestrisagainst importation of bumble bees of foreign origin which are used as crop p

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00288.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractWe studied effects of physical isolation on geographical variation in mtDNA RFLP polymorphisms and a suite of morphological characters within three species of neotropical forest birds; the crimson‐backed tanagerRamphocelus dimidiatus, the blue‐gray tanagerThraupis episcopus, and the streaked saltatorSaltator albicollis. Variation among populations within continuous habitat on the Isthmus of Panama was compared with that among island populations isolated for about 10000 years. Putative barriers to dispersal were influential, but apparent isolation effects varied by species, geographical scale, and whether molecular or morphological traits were being assessed. We found no geographical structuring among the contiguous, mainland sampling sites. Migration rates among the islands appeared sufficient to maintain homogeneity in mtDNA haplotype frequencies. In contrast, variation in external morphology among islands was significant within two of three species. For all species, we found significant variation in genetic and morphological traits between the island (collectively) and mainland populations. Interspecific variation in the effects of isolation was likely related to differential vagility. These data generally corroborate other studies reporting relatively great geographical structuring within tropical birds over short distances. Behaviourally based traits ‐ low vagility and high ‘sensitivity’ to geographical barriers ‐ may underlie extensive diversification within neotropical forest birds, but more extensive ecological and phylogeographic information are needed on a diverse sample

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00289.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractWe used 11 restriction endonucleases to study mtDNA variation in 101 Dall's porpoisesPhocoenoides dallifrom the Bering Sea and western North Pacific. There was little phylogeographic patterning among the 34 mtDNA haplotypes identified in this analysis, suggesting a strong historical connection among populations across this region. Nonetheless, mtDNA variation does not appear to be randomly distributed in this species. BothGSTand AMOVA uncovered significant differences in the distribution of mtDNA variation between the Bering Sea and western North Pacific populations. These mtDNA results, coupled with differences in allozyme variation and parasite infestation, support the demographic distinctiveness of Bering Sea and western North Pacific stocks of Dall's porpoise. The lack of a strong phylogeographic orientation of mtDNA haplotypes within the Dall's porpoise is similar to the pattern reported in other vertebrates such as coyotes, blackbirds, chickadees, marine catfish, and catadromous eels. Like Dall's porpoise, these species are broadly distributed, and have large populations linked by moderate to high levels of gene flow. However, the more complex, deeply branched phylogenetic network of mtDNA haplotypes within Dall's porpoise, relative to these other vertebrates, suggests important differences between these species in the forces shaping mtDNA variation. One such force is the effective size of female populations, which appears to have been comparatively large and stable in Dall's porpoise.

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00290.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThymus vulgarisis a gynodioecious species (in which females and hermaphrodites coexist) with a highly variable frequency of females among natural populations (5–95%) and a high average female frequency (60%). Sex determination involves both cytoplasmic genes responsible for male sterility, i.e. the female phenotype, and specific nuclear factors responsible for the restoration of male fertility, and thus a hermaphrodite phenotype. In this study, molecular markers of the mitochondrial genome have been used to quantify the cytoplasmic diversity in 11 clumps of individuals observed in four recently founded populations. The very low diversity within patches in conjunction with the strong diversity among patches strongly suggests that clumps of individuals are the result of single matrilinear families. In clumps that contain mainly females, all the analysed females showed the same cytoplasmic pattern. This pattern differed from that shown by neighbouring hermaphrodites, indicating that the determination of sex is locally cytoplasmic. A comparison of genetic diversity before and after fire in one population showed that disturbances may cause a reduction in genetic diversity and a concurrent induction of local cytoplasmic determination of sex. Such cytoplasmic determination of sex in colonizing populations, together with the greater seed set of females, may largely improve the colonizing ability of the specie

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00291.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractSystemic acquired resistance (SAR) and microbial biocontrol each hold promise as alternatives to pesticides for control of plant diseases. SAR andBacillus cereusUW85, a microbial biocontrol agent, separately suppress seedling damping‐off diseases caused by oomycete pathogens. The purposes of this study were to investigate how expression of SAR affected the efficacy of biocontrol by UW85 and if UW85 treatment of plants induced SAR. We devised a laboratory assay in which seedling damping‐off disease, induction of SAR, and growth of UW85 could be quantified. Seedlings ofNicotiana tabacumXanthi nc were germinated on moist filter paper and transferred after 7 days to water agar plates (40 seedlings per plate). Zoospores of oomycete pathogens (Pythium torulosum, Pythium aphanidermatum, orPhytophthora parasitica) were applied at concentrations that caused 80% seedling mortality within 10 days. Seedling mortality was dependent on zoospore inoculum concentration. The level of disease suppression caused by treatment with UW85 depended on the UW85 dose applied. SAR was induced with 0.5‐mM salicylic acid or 0.1‐mM 2,6‐dichloroisonicotinic acid. Expression of an SAR‐related gene was confirmed by northern analysis with a probe prepared from a tobacco PR‐1a cDNA. Induction of SAR suppressed disease caused by each of the oomycete pathogens, but did not alter the growth of UW85 on roots. Treatment of seedlings with UW85 did not induce the expression of PR‐1a. The combination of induction of SAR and treatment with UW85 resulted in additive suppression of disease as measured by se

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00292.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractPredation by the red foxVulpes vulpesis believed to be threatening the little penguinEudyptula minoron Phillip Island in Victoria. Polymorphism at seven microsatellite loci was examined to estimate the extent of differentiation between Phillip Island and mainland populations ofV. vulpes. Loss of alleles has occurred on Phillip Island where foxes first appeared = 88 years ago compared with mainland populations. Genetic differentiation between the Phillip Island and mainland populations was high. The relatively high differentiation found between the two populations could be due to either low migration rates, the effect of the composition of founder animals or both effects. Further ecological and historical information about the populations is needed to explore the likely significance of these effects.

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1996.tb00293.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY