摘要:

AbstractInformation on the reproductive behaviour and population structure of female hawksbill turtles,Eretmochelys imbricata, is necessary to define conservation priorities for this highly endangered species. Two hypotheses to explain female nest site choice, natal homing and social facilitation, were tested by analysing mtDNA control region sequences of 103 individuals from seven nesting colonies in the Caribbean and western Atlantic. Under the social facilitation model, newly mature females follow older females to a nesting location, and subsequently use this site for future nesting. This model generates an expectation that female lineages will be homogenized among regional nesting colonies. Contrary to expectations of the social facilitation model, mtDNA lineages were highly structured among western Atlantic nesting colonies. These analyses identified at least 6 female breeding stocks in the Caribbean and western Atlantic and support a natal homing model for recruitment of breeding females. Reproductive populations are effectively isolated over ecological time scales, and recovery plans for this species should include protection at the level of individual nesting colonies.

ISSN:0962-1083    

DOI:10.1046/j.1365-294X.1996.00073.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractWe used sequence variation within 297 bp of control region mitochondrial DNA (mtDNA) amplified from 53 lesser long‐nosed bats,Leptonycteris curasoae(Phyllostomidae: Glossophaginae) captured at 13 locations in south‐western United States and Mexico and one site in Venezuela to infer population structure and possible migration routes of this endangered nectar‐ and fruit‐eating species. Phylogenetic analysis using maximum parsimony and UPGMA confirmed species and subspecies distinctions withinLeptonycterisand revealed two clades exhibiting 3% sequence divergence within the Mexican subspecies,L. c. yerbabuenae. Even though many roosts containedL. c. yerbabuenaefrom both clades, weak population structure was detected both by a correlation between genetic differentiation,Fstrand geographical distance and by a cladistic estimate of the number of migration events required to align bat sequences with geographical location on maximum parsimony, as compared to random, trees. Three results suggest thatL. c. yerbabuenaeare more likely to migrate between sites along the Pacific coast of Mexico or along the foothills of the Sierra Madre Occidental than between these regions. (1) Seventeen of 20 bats which shared an identical sequence were captured up to 1800 km apart but within the same putative migration corridor. (2) Residuals from a regression ofFston distance were greater between than within these regions. (3) Fewer migration events were required to align bats with these two groups than expected from random assignment. We recommend analysing independent genetic data and monitoring bat visitation to roost sites during migration to confirm these postulated mo

ISSN:0962-1083    

DOI:10.1046/j.1365-294X.1996.00081.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe spectacularly diverse cichlid fish species flocks of the East African Rift Lakes have elicited much debate on the potential evolutionary mechanisms responsible for the origin of these adaptive radiations. An historical perspective on population structure may offer insights into the processes driving population differentiation and possibly speciation. Here, we examine mitochondrial DNA (mtDNA) sequence variation in two endemic species of rock‐dwelling cichlids,Simochromis babaultiandS. diagramma, from Lake Tanganyika. Phylogeographic analyses were used to infer what factors might have been important in the genetic structuring ofSimochromispopulations. Patterns of mtDNA differentiation inSimochromiswere compared to those of other rock‐dwelling cichlids to distinguish between competing hypotheses concerning the processes underlying their evolution. In striking contrast to previous findings, populations ofSimochromis, even those separated by up to 300 km, were found to share mitochondrial DNA haplotypes. There is no correspondence between mtDNA genealogies and the geographical distribution of populations. OnlyS. babaulti, but notS. diagrammawas found to have a significant association between genetic and geographical distance. These phylogeographic patterns suggest that the evolutionary effects of abiotic and biotic factors shaping population genetic structure may differ substantially even among closely related species of rock‐dwelling cichlids. Physical events and barriers to gene flow that are believed to have had a major impact on the geographical distribution and intralacustrine speciation ofTropheusdo not seem to have equally strongly affected its close relativeSimochromis. These findings emphasize that no single mechanism can be responsible for the formation of population structure, speciation, and the adaptive radiation of all cichlid f

ISSN:0962-1083    

DOI:10.1046/j.1365-294X.1996.00093.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractPhylogenetic relationships among species ofAeoniumwere studied using morphological characters and chloroplast DNA RFLPs. Cladistic analysis of weighted morphological data indicates that the small, herbaceous and least woody species are basal in the genus. Chloroplast DNA data gave similar results, supporting the separation of the herbaceous or small, woody species from the large, hapaxanth rosettes, rosette trees, and branched subshrubs with yellow, white or red flowers as well as the only (herbaceous) species with axillary inflorescences. The relationships among the species descending from a polytomy that comprises all species of the genus as well as a polytomy which comprises 18 of the 26 species studied, are only very incompletely resolved, except for two monophyletic clades that contain the branched subshrubs with yellow flowers (A.sect.Aeonium) and the branched subshrubs and rosette trees with white or red flowers (A.sect.Leuconium), respectively. Cladistic analysis of the combined morphological and chloroplast DNA data improved resolution considerably. Four monophyletic clades are distinguished, each of which, except for three species, comprises only one of the five main growth‐form types. AlthoughAeoniumis generally regarded as an outstanding example of adaptive radiation, this mode of speciation seems to have been of minor significance in the evolution of the genus, because each growth‐form apparently evolved only once. Instead, island speciation in the absence of major ecological shifts, is probably more important in the evolution of the ge

ISSN:0962-1083    

DOI:10.1046/j.1365-294X.1996.00090.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe possibility to perform cross‐species microsatellite amplification in birds was surveyed by analysing sets of primers developed from the swallow and the pied flycatcher genomes on a panel of 48 different bird species. In total, 162 cases (species/marker combinations) of heterologous amplification were recorded. Ten amplification products were sequenced and all were found to be true homologues of the original loci. There was a significant and negative relationship between microsatellite performance and evolutionary distance between the original species and the tested species. As a rough indicator of expected cross‐species microsatellite performance we estimate that 50% of markers will reveal polymorphism in a species with a DNA‐DNA hybridization δTmH value of 5 separating it from the original species. This corresponds to a divergence time of = 11 million years before present for passerine birds. The established relationship between performance and evolutionary distance agrees very well with data obtained from some mammalian species. The proportion of polymorphic loci among those markers that amplified decreased with increasing genetic distance, suggesting that few long repeats are preserved during evolution. One of the swallow markers,HrU2, amplified a specific product in all species analysed and will thus allow access to nuclear sequence data over a broad range of species. The only predictor of cross‐species performance was the amount of non‐specific amplification seen in the original species. An analysis of 10 species from within the family Hirundinidae with the swallow primers consistently revealed extensive polymorphism with average probabilities of identical genotypes ranging from 6 times 10‐4to 6 times 10‐7. There were distinct allele frequency differences between the Hirundinidae species and we envisage that microsatellite cross‐species amplification will be a useful tool in phylogeny construction and in specie

ISSN:0962-1083    

DOI:10.1046/j.1365-294X.1996.00092.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractLizards of theSceloporus grammicuscomplex are comprised of multiple chromosome races that form several zones of parapatric hybridization in central Mexico. We scored diagnostic mitochondrial DNA (mtDNA) haplotypes and autosomal chromosome markers in a sample of 342 lizards from one well‐defined zone between 2n = 34 and 2n = 46 races. A two‐part analysis was performed on this data set in an attempt to infer the predominant evolutionary forces shaping the cytonuclear structure of this zone. The complications posed by its spatial structure were addressed by analysing a hierarchical series of smaller subsamples chosen to approximate single mating units. Two critical conclusions were drawn from this first‐stage analysis. First and foremost, the three chromosomes have largely concordant cytonuclear disequilibrium patterns within each subsample with adequate numbers of individuals for detecting nonrandom cytonuclear associations. This suggests that the cytonuclear structure of this zone is predominantly a result of deterministic genome‐wide forces rather than genetic drift or deterministic forces specific to individual chromosomes or loci. Second, the fit of a series of migration models to the data shows that the cytonuclear structure of the subsamples is well accounted for by continued gene flow from the two parental races alone, with random mating with respect to cytonuclear genotype and no other evolutionary forces. These results motivate several further empirical and theoretical investigations to refine our understanding of the relative roles of migration and other potentially important forces such as natural selection and genetic drift, in this and other hybri

ISSN:0962-1083    

DOI:10.1046/j.1365-294X.1996.00091.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThis study investigates the use of microsatellite loci for estimating relatedness between individuals in wild, outbred, vertebrate populations. We measured allele frequencies at 20 unlinked, dinucleotide‐repeat microsatellite loci in a population of wild mice (Mus musculus), and used these observed frequencies to generate the expected distributions of pairwise relatedness among full sib, half sib, and unrelated pairs of individuals, as would be estimated from the microsatellite data. In this population one should be able to discriminate between unrelated and full‐sib dyads with at least 97% accuracy, and to discriminate half‐sib pairs from unrelated pairs or from full‐sib pairs with better than 80% accuracy. If one uses the criterion that parent‐offspring pairs must share at least one allele per locus, then only 15% of full‐sib pairs, 2% of half‐sib pairs, and 0% of unrelated pairs in this population would qualify as potential parent‐offspring pairs. We verified that the simulation results (which assume a random mating population in Hardy‐Weinberg and linkage equilibrium) accurately predict results one would obtain from this population in real life by scoring laboratory‐bred full‐ and half‐sib families whose parents were wild‐caught mice from the study population. We also investigated the effects of using different numbers of loci, or loci of different average heterozygosities (He), on misclassification frequencies. Both variables have strong effects on misclassification rate. For example, it requires almost twice as many loci ofHe= 0.62 to achieve the same accuracy as a given number of loci ofHe= 0.75. Finally, we tested the ability of UPGMA clustering to identify family groups in our population. Clustering of allele matching scores among the offspring of four sets of independent maternal half sibships (four females, each mated to two different males) perfectly recovered the

ISSN:0962-1083    

DOI:10.1046/j.1365-294X.1996.00094.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractA highly polymorphic locus in the honey bee,Apis melliferaL., was detected with genomic probe pB178. Eighty‐five alleles, consisting ofMspI andDdeI RFLPs, were found among the Old and New World bees tested. Forty‐oneMspI and 43DdeI restriction fragment patterns, or variants, were identified. Variants and alleles were discontinuously distributed in Old World European and African subspecies. Principal coordinate analysis of the genetic distances between the alleles resulted in the identification of three distinct groups corresponding to three groups of honey bee races with historically different geographical distributions: east EuropeanA. m. ligusticaandA. m. caucasica; west EuropeanA. m. mellifera; and South AfricanA. m. scutellata. The clustering of alleles into these groups is consistent with previous honey bee phylogeographic studies, employing other nuclear and mitochondrial DNA markers, which in part support the evolutionary history of the honey bee hypothesized by Ruttner based on morphometric and allozyme data. The majority of alleles in bees from the USA grouped with those found in east European bees, while other alleles grouped with alleles found inA. m. mellifera. While the majority of the alleles in neotropical bees grouped with or were identical to African alleles, other alleles grouped with alleles found inA. m. mellifera, A. m. ligustica, andA. m. caucasica. Clues to the ancestry of neotropical bees may be found in the identification of alleles that were identical or more similar to alleles found in South African and west European bees; evidence for west European ancestry has been suggested using other taxonomic characters that were not unique to west European bees. Both west European and African alleles were found in individual neotropical colonies, which may indicate that honey bee subspecies which evolved allopatrically have hybridized in the human‐assisted extension of their original geographical r

ISSN:0962-1083    

DOI:10.1046/j.1365-294X.1996.00100.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractIn the Doubs River (Rhone drainage) two distinct brown trout (S. trutta) phenotypes are observed. One phenotype is locally called Doubs trout and is characterized by four black stripes on the sides, similar to perch (Perca fluviatilisL.) and the other is the common phenotype of the fluviatile ecotype of brown trout,Salmo truttaf.fario. Protein data for three samples from the Doubs show that the Doubs trout belongs to the Mediterranean population group of brown trout, whereas thefariophenotype originates from stocking with hatchery strains of Atlantic basin origin. The two forms, however, do not hybridize freely. This is indicated by considerable gametic phase disequilibrium between alleles of hatchery and Doubs trout at one sampling site, and by lack of intermediate genotypes and phenotypes at another sampling site. The introgression patterns observed at the two sites suggest that differences in local habitat conditions can affect the degree of hybridization and introgression.

ISSN:0962-1083    

DOI:10.1046/j.1365-294X.1996.00099.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThis paper describes how groundwater was sampled, DNA extracted, amplified and cloned and how information available in the ribosomal 16S rRNA gene was used for mapping diversity and distribution of subterranean bacteria in groundwater at the Bangombé site in the Oklo region. The results showed that this site was inhabited by a diversified population of bacteria. Each borehole was dominated by species that did not dominate in any of the other boreholes; a result that probably reflects documented differences in the geochemical environment. Two of the sequences obtained were identified at genus level to representAcinetobacterandZoogloea, but most of the 44 sequences found were only distantly related to species in the DNA database. The deepest borehole, BAX01 (105 m), had the highest number of bacteria and also total organic carbon (TOC). This borehole harboured only Proteobacteria beta group sequences while sequences related to Proteobacteria beta, gamma and delta groups and Gram‐positive bacteria were found in the other four boreholes. Two of the boreholes, BAX02 (34 m) and BAX04 (10 m) had many 16S rRNA gene sequences in common and they also had similar counts of bacteria, content of TOC, pH and equal conductivity, suggesting a hydraulic connection between th

ISSN:0962-1083    

DOI:10.1046/j.1365-294X.1996.d01-320.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY