bluuebunny/crossref_metadata_2025_split huggingface dataset:
Species‐specific detection ofLobaria pulmonaria(lichenized ascomycete) diaspores in litter samples trapped in snow cover
Authors: Walser J.‐C. , Zoller S. , Büchler U. , Scheidegger C. 
Published: March 2003

AbstractThe foliose lichenLobaria pulmonariahas suffered a substantial decline in central and northern Europe during the twentieth century and is now considered to be critically endangered in many European lowland regions. Based on demographic studies, it has been proposed that under the present environmental conditions and forest management regimes, dispersal of diaspores and subsequent establishment of new thalli are insufficient to maintain the remnant small lowland populations. Chances of long‐term survival may therefore be reduced. The data and analytical power of these demographic studies are limited. Since lichen diaspores show very few species‐specific morphological characteristics, and are therefore almost indistinguishable, the accurate assessment of diaspore flux would be a fundamental first step in better understanding the life cycle ofL. pulmonaria. Here we present a new molecular approach to investigate the dispersal ofL. pulmonariadiaspores in its natural environment by specifically identifying small amounts of DNA in snow litter samples at varying distances from known sources. We used a species‐specific polymerase chain reaction (PCR) primer pair to amplify the ribosomal internal transcribed spacer region (ITS rDNA) and a sensitive automated PCR product detection system using fluorescent labelled primers. We detected considerable amounts of naturally dispersed diaspores, deposited as far as 50 m away from the closest potential source. Diaspores were only found in the direction of the prevailing wind. Diaspore deposition varied from 1.2 diaspores per m2per day at 50 m distance from the source to 15 diaspores per m2per day at 1 m distance. The method described in this paper opens up perspectives for studies of population dynamics and dispersal ecology mainly in lichenized ascomycetes but also in other organisms with small, wind‐dispersed diaspores.
Intraspecific phylogeography of Percina evides (Percidae: Etheostomatinae): an additional test of the Central Highlands pre‐Pleistocene vicariance hypothesis
Authors: Near Thomas J. , Page Lawrence M. , Mayden Richard L. 
Published: March 2003

AbstractNorth America exhibits the most diverse freshwater fish fauna among temperate regions of the world. Species diversity is concentrated in the Central Highlands, drained by the Mississippi, Gulf Slope and Atlantic Slope river systems. Previous investigations of Central Highlands biogeography have led to conflicting hypotheses involving dispersal and vicariance to explain the diversity and distribution of the freshwater fish fauna. In this investigation predictions of the Central Highlands pre‐Pleistocene vicariance hypothesis are tested with a phylogeographic analysis of the percid species Percina evides, which is widely distributed in several disjunct areas of the Central Highlands. Phylogenetic analysis of complete gene sequences of mitochondrially encoded cytochrome b recover three phylogroups, with very low levels of sequence polymorphism within groups. The two western phylogroups are monophyletic with respect to the eastern phylogroup. The recovery of two monophyletic lineages with an eastern and western distribution in the disjunct highland areas is a pattern expected from vicariance, but is not predicted by the Central Highlands pre‐Pleistocene vicariance hypothesis. The recovery of very limited mitochondrial DNA polymorphism and lack of phylogeographic structuring across the entire range of the eastern clade, very shallow polymorphism between the disjunct Missouri River and upper Mississippi River populations, and lack of sequence polymorphism in the upper Mississippi River populations, support a hypothesis of dispersal during or following the Pleistocene. The present distribution of P. evides is best explained by both vicariant and dispersal events.
The contribution of haploids, diploids and clones to fine‐scale population structure in the seaweedCladophoropsis membranacea(Chlorophyta)
Authors: Van Der Strate H. J. , Van De Zande L. , Stam W.T. , Olsen J. L. 
Published: March 2003

AbstractLocal populations ofCladophoropsis membranaceaexist as mats of coalesced thalli composed of free‐living haploid and diploid plants including clonally reproduced plants of either phase. None of the phases are morphologically distinguishable. We used eight microsatellite loci to explore clonality and fine‐scale patch structure inC. membranaceaat six sites on the Canary Islands. Mats were always composites of many individuals; not single, large clones. Haploids outnumbered diploids at all sites (from 2:1 to 10:1). In both haploid and diploid plants, genetic diversity was high and there was no significant difference in allele frequencies. Significant heterozygote deficiencies were found in the diploid plants at five out of six sites and linkage disequilibrium was associated with the haploid phase at all sites. Short dispersal distances of gametes/spores and small effective population sizes associated with clonality probably contribute to inbreeding. Spatial autocorrelation analysis revealed that most clones were found within a radius of ≈ 60 cm and rarely further than 5 m. Dominance of the haploid phase may reflect seasonal shifts in the relative frequencies of haploids and diploids, but may alternatively reflect superiority of locally adapted and competitively dominant, haploid clones; a strategy that is theoretically favoured in disturbed environments. Although sexual reproduction may be infrequent inC. membranacea, it is sufficient to maintain both life history phases and supports theoretical modelling studies that show that haploid–diploid life histories are an evolutionarily stable strategy.
Mitochondrial DNA variation in a species with two mitochondrial genomes: the case of Mytilus galloprovincialis from the Atlantic, the Mediterranean and the Black Sea
Authors: Ladoukakis E.D. , Saavedra C. , Magoulas A. , Zouros E. 
Published: March 2003

AbstractWe have examined mitochondrial DNA (mtDNA) variation in samples of the mussel Mytilus galloprovincialis from the Black Sea, the Mediterranean and the Spanish Atlantic coast by scoring for presence or absence of cleavage at 20 restriction sites of a fragment of the COIII gene and at four restriction sites of the 16S RNA gene. This species contains two types of mtDNA genomes, one that is transmitted maternally (the F type) and one that is transmitted paternally (the M type). The M genome evolves at a higher rate than the F genome. Normally, females are homoplasmic for an F type and males are heteroplasmic for an F and an M type. Occasionally molecules from the F lineage invade the paternal transmission route, resulting in males that carry two F‐type mtDNA genomes. These features of the mussel mtDNA system give rise to a new set of questions when using mtDNA variation in population studies and phylogeny. We show here that the two mtDNA types provide different information with regard to amounts of variation and genetic distances among populations. The F genome exhibits higher degrees of diversity within populations, while the M genome produces higher degrees of differentiation among populations. There is a strong differentiation between the Atlantic and the Black Sea. The Mediterranean samples have intermediate haplotype frequencies, yet are much closer to the Black Sea than to the Atlantic. We conclude that in this species gene flow among the three Seas is restricted and not enough to erase the combined effect of mutation and random drift. In one sample, that from the Black Sea, the majority of males did not contain an M mtDNA type. This suggests that a molecule of the maternal lineage has recently invaded the paternal route and has increased its frequency in the population to the point that the present pool of paternally transmitted mtDNA molecules is highly heterogeneous and cannot be used to read the population’s history. This liability of the paternal route means that in species with doubly uniparental inheritance, the maternal lineage provides more reliable information for population and phylogenetic studies.
Reconstructing recent divergence: evaluating nonequilibrium population structure in New Zealand chinook salmon
Authors: Kinnison M. T. , Bentzen P. , Unwin M. J. , Quinn T. P. 
Published: March 2003

AbstractNewly established or perturbed populations are often the focus of conservation concerns but they pose special challenges for population genetics because drift−migration equilibrium is unlikely. To advance our understanding of the evolution of such populations, we investigated structure and gene flow among populations of chinook salmon that formed via natural straying following introduction to New Zealand in the early 1900s. We examined 11 microsatellite loci from samples collected in several sites and years to address two questions: (i) what population differentiation has arisen in the ≈ 30 generations since salmon were introduced to New Zealand, relative to temporal variation within populations; and (ii) what are the approximate effective population sizes and amounts of gene flow in these populations? These questions are routinely addressed in studies of indigenous populations, but less often in the case of new populations and rarely with consideration of equilibrium assumptions. We show that despite the recent introduction, continued gene flow and high temporal variability among samples, detectable population structure has arisen among the New Zealand populations, consistent with their colonization pattern and isolation by geographical distance. Furthermore, we use simple individual‐based simulations and estimates of effective population sizes to estimate the effective gene flow among drainages under likely nonequilibrium conditions. Similar methodology may be broadly applicable to other studies of population structure and phenotypic evolution under similar nonequilibrium, high gene flow conditions.
Tests for sex‐biased dispersal using bi‐parentally inherited genetic markers
Authors: Goudet Jérôme , Perrin Nicolas , Waser Peter 
Published: March 2003

AbstractUnderstanding why dispersal is sex‐biased in many taxa is still a major concern in evolutionary ecology. Dispersal tends to be male‐biased in mammals and female‐biased in birds, but counter‐examples exist and little is known about sex bias in other taxa. Obtaining accurate measures of dispersal in the field remains a problem. Here we describe and compare several methods for detecting sex‐biased dispersal using bi‐parentally inherited, codominant genetic markers. If gene flow is restricted among populations, then the genotype of an individual tells something about its origin. Provided that dispersal occurs at the juvenile stage and that sampling is carried out on adults, genotypes sampled from the dispersing sex should on average be less likely (compared to genotypes from the philopatric sex) in the population in which they were sampled. The dispersing sex should be less genetically structured and should present a larger heterozygote deficit. In this study we use computer simulations and a permutation test on four statistics to investigate the conditions under which sex‐biased dispersal can be detected. Two tests emerge as fairly powerful. We present results concerning the optimal sampling strategy (varying number of samples, individuals, loci per individual and level of polymorphism) under different amounts of dispersal for each sex. These tests for biases in dispersal are also appropriate for any attribute (e.g. size, colour, status) suspected to influence the probability of dispersal. A windows program carrying out these tests can be freely downloaded from http://www.unil.ch/izea/softwares/fstat.html
New insights into the distribution of polyploid Daphnia: the Holarctic revisited and Argentina explored
Authors: Adamowicz Sarah J. , Gregory T. Ryan , Marinone María Cristina , Hebert Paul D. N. 
Published: March 2003

AbstractIt has long been known that polyploid organisms are more prevalent in arctic than in temperate environments. Past explanations for this geographical trend have focused on the role of glacial cycles in generating polyploids and the influence of abiotic factors in favouring polyploidy in the north. In combination, these mechanisms probably suffice to explain the observed geographical cline in ploidy levels in members of the Daphnia pulex complex in the Holarctic. While only diploid members of the D. pulex complex are found in the temperate regions of North America and Europe, allozyme and DNA quantification analyses indicate that the southern Argentine pulex‐complex fauna is dominated by polyploids. Indeed, the present study is the first to document the presence of polyploid members of the D. pulex complex in any temperate climate. The results of phylogeographic analyses suggest that this difference in polyploid distribution between the northern and southern hemispheres is based more on ecological and historical contingencies than direct selection for polyploidy. Specifically, competition with diploid relatives probably limits the lower latitudinal range of polyploids in the north, but appears not to have occurred in Argentina. Because of these differences, the present study provides important insights into the diverse factors that determine the distributions and evolutionary fates of polyploid organisms.
Historical biogeography and molecular systematics of the Indo‐Pacific genus Dascyllus (Teleostei: Pomacentridae)
Authors: McCafferty S. , Bermingham E. , Quenouille B. , Planes S. , Hoelzer G. , Asoh K. 
Published: March 2003

AbstractThe phylogeographical and systematic relationships among species in the tropical marine fish genus Dascyllus were inferred using mitochondrial DNA (mtDNA) sequence data. Although our results were generally consistent with previously published phylogenies based on both morphological and mitochondrial data, our broad taxonomic and geographical sampling design revealed novel insights into the phylogenetic history of Dascyllus that had escaped previous notice. These results include: (a) the polyphyletic nature of D. reticulatus mtDNAs, representing two divergent and geographically separated lineages, one shared with D. flavicaudus and the second forming the sister lineage of D. carneus; (b) the paraphyly of D. trimaculatus relative to the closely related D. abisella; and (c) phylogeographical structure within the widespread taxa D. aruanus and D. trimaculatus. Application of a molecular clock permits us to posit a causative role for tectonic and oceanic changes regarding some Dascyllus speciation events. Finally, we mapped body size and the presence or absence of protogynous sex change on the mtDNA tree, and tested published hypotheses regarding determinants of the evolution of mating system and protogyny in the genus. Our data rejected a model based on body size but not one based on phylogenetic inertia. The ability to change sex arose once in the ancestor to the entire genus, and was lost once in the ancestor of the D. trimaculatus complex. For taxa that are as geographically widespread as many Indo‐Pacific genera, this study highlights the importance of adequate geographical sampling when inferring patterns of species diversification and life history evolution.
Hybrid status of kuwini, Mangifera odorata Griff. (Anacardiaceae) verified by amplified fragment length polymorphism
Authors: Teo L. L. , Kiew R. , Set O. , Lee S. K. , Gan Y. Y. 
Published: March 2003

Abstract Mangifera odorata Griff. (Anacardiaceae), was suggested to be a hybrid between M. indica L. and M. foetida Lour. due to morphological intermediacy. Results from this study show that M. indica and M. foetida produced unique amplified fragment length polymorphism (AFLP) profiles. Mangifera odorata did not produce any unique bands. All the M. odorata samples additively inherit bands specific to M. indica and M. foetida, which strongly suggested the hybrid origin. Three major clusters were produced in the phenogram. All samples of M. indica, M. foetida and M. odorata segregated distinctly. Mangifera odorata was closer to M. foetida than to M. indica, indicating that backcrossing with M. foetida might have taken place. AFLP analysis therefore verified the hybrid status of M. odorata.
Late glacial history of the cold‐adapted freshwater fish Cottus gobio, revealed by microsatellites
Authors: Hänfling B. , Hellemans B. , Volckaert F. A. M. , Carvalho G. R. 
Published: March 2003

AbstractThe distribution of genetic diversity at 10 highly polymorphic microsatellite loci within the European freshwater fish, Cottus gobio, L. was examined. The sampling range comprised a large geographical scale including lineages known to be highly divergent at both mitochondrial DNA (mtDNA) and allozymes. An analysis of genetic variability within populations showed that expected heterozygosity and allelic richness could be explained largely by current effective population sizes. Evidence was found, however, that historical processes predating the last major glaciation affected allelic richness. In addition to confirming the large‐scale patterns from earlier studies, the microsatellite data revealed new insights into recent processes by analysing genetic structure within ancient lineages defined by mtDNA data. Stepwise mutation model (SMM) and nonSMM‐based methods demonstrated a clear genetic structuring within the Northwestern European lineage comprising populations from Britain and Belgium, and within the Central European lineage populations from the rivers Danube, Elbe and Main. Supported by an analysis of genetic variability within populations these results showed that the bullhead populations most probably persisted throughout the last major glaciation within the British Isles and within the drainages of the rivers Elbe and Main. Such observations provide the first genetic evidence for a glacial refugium in such close proximity to the European glacial margins.
Homoplasy and mutation model at microsatellite loci and their consequences for population genetics analysis
Authors: Estoup Arnaud , Jarne Philippe , Cornuet Jean‐Marie 
Published: March 2003

AbstractHomoplasy has recently attracted the attention of population geneticists, as a consequence of the popularity of highly variable stepwise mutating markers such as microsatellites. Microsatellite alleles generally refer to DNA fragments of different size (electromorphs). Electromorphs are identical in state (i.e. have identical size), but are not necessarily identical by descent due to convergent mutation(s). Homoplasy occurring at microsatellites is thus referred to as size homoplasy. Using new analytical developments and computer simulations, we first evaluate the effect of the mutation rate, the mutation model, the effective population size and the time of divergence between populations on size homoplasy at the within and between population levels. We then review the few experimental studies that used various molecular techniques to detect size homoplasious events at some microsatellite loci. The relationship between this molecularly accessible size homoplasy size and the actual amount of size homoplasy is not trivial, the former being considerably influenced by the molecular structure of microsatellite core sequences. In a third section, we show that homoplasy at microsatellite electromorphs does not represent a significant problem for many types of population genetics analyses realized by molecular ecologists, the large amount of variability at microsatellite loci often compensating for their homoplasious evolution. The situations where size homoplasy may be more problematic involve high mutation rates and large population sizes together with strong allele size constraints.
Mitochondrial pseudo‐control region in old world eagles (genus Aquila)
Authors: Väli Ü. 
Published: March 2003

AbstractThe mitochondrial pseudo‐control region was analysed in five species of Aquila eagles. Indels caused great length differences in the nonrepetitive part of the region, whereas tandem repeat units were highly conserved among the genus. In a reconstructed phylogenetic tree, the clade formed by A. clanga and A. pomarina showed approximately the same distance to A. chrysaetos as did the clade A. heliaca/nipalensis. In Estonian subpopulations, 12 haplotypes were found among 51 A. pomarina individuals and 7 haplotypes among 8 A. clanga individuals. Nucleotide diversity in A. clanga was greater, and may be caused by decreased breeding density or by gene flow from other subpopulations.
A genetic method to resolve gender complements investigations on sex ratios in Rumex acetosa
Authors: Korpelainen Helena 
Published: March 2003

AbstractThe perennial dioecious weed, Rumex acetosa, possesses sex chromosomes (XX in females, XY1Y2 in males). Yet, the operational sex ratios are female‐biased. Until now, sex ratio studies in R. acetosa, as in most plants, have relied on data obtained at sexual maturity. To resolve gender among the seeds and nonflowering plants of R. acetosa, a genetic method involving a DNA marker located on both Y chromosomes has now been developed and applied. The results suggest that the sex ratios are about 1 : 1 in the whole seed pool, but that a significant female bias develops by the time of flowering. Since the age of sexually mature plants is two years or more, the time frame during which the female bias present at sexual maturity develops can be several years. It appears that male seeds germinate at a lower rate and males suffer from a greater mortality during the years‐long lifespan of R. acetosa. However, there are no considerable sex‐related differences in vegetative vigour.
Nunatak survival of the high Alpine plant Eritrichium nanum (L.) Gaudin in the central Alps during the ice ages
Authors: Stehlik I. , Blattner F. R. , Holderegger R. , Bachmann K. 
Published: March 2003

AbstractPolymerase chain reaction–restriction fragment length polymorphisms (PCR‐RFLPs) and sequence analysis of noncoding regions of chloroplast DNA were used to investigate 37 populations of Eritrichium nanum covering its total distribution area, the European Alps. There was no haplotypic variation within the populations, and most haplotypes were restricted to single sites or to neighbouring populations, suggesting low levels of long distance gene flow via seeds. The present geographical distribution of haplotypes probably reflects an ancient geographical pattern within two regions in the intensely glaciated western and eastern central Alps identified as genetic hotspot areas. These two regions contained seven of the total of 11 haplotypes, including many of the most derived ones. The divergent haplotypes formed closely related groups, which supported a separate evolution of these haplotypes in these two regions and, more importantly, gave strong evidence for the in situ survival of these populations on nunataks within the western and eastern central Alps during Pleistocene glaciation. This result is in concordance with a previous study on E. nanum using nuclear markers. Only one haplotype was common and widespread throughout the distributional range of E. nanum. At the same time, it was the evolutionarily basal‐most and all other haplotypes were best described as its descendants. This haplotype is hypothesized to be genetically identical to a Tertiary Alpine colonizing ancestor, whose distribution was secondarily fragmented and infiltrated by derived haplotypes originating through local mutations.