bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variation on islands: major histocompatibility complex (Mhc) polymorphism in populations of the Australian bush rat
Authors: Seddon J. M. , Baverstock P. R. 
Published: March 2003

AbstractLoss of genetic variation in small, isolated populations is commonly observed at neutral or nearly neutral loci. In this study, the loss of genetic variation was assessed in island populations for a locus of major histocompatibility complex (Mhc), a locus shown to be under the influence of balancing selection. A total of 36 alleles was found at the second exon ofRT1.Bain 14 island and two mainland populations ofRattus fuscipes greyii. Despite this high overall diversity, a substantial lack of variation was observed in the small island populations, with 13 islands supporting only one to two alleles. Two populations, Waldegrave and Williams Islands, showed moderately high levels of heterozygosity (52–56%) which were greater than expected under neutrality, suggesting the action of balancing selection. However, congruence between the level of variation at thisMhclocus and in previous allozyme electrophoresis and mitochondrial DNA studies highlights the dominant influence of genetic drift and population factors, such as bottlenecks and structuring in the founding population, in the loss of genetic variation in these small, isolated populations.
Assessment of natural and artificial propagation of the white‐clawed crayfish (Austropotamobius pallipes species complex) in the Alpine region with nuclear and mitochondrial markers
Authors: Largiadèr C. R. , Herger F. , Lörtscher M. , Scholl A. 
Published: March 2003

AbstractIn a joint analysis of nuclear (allozyme) and mitochondrial markers (sequence and restriction fragment length polymorphism (RFLP) analysis of the 12S and 16S genes), five genetically distinct groups of the Austropotamobius pallipes Lereboullet species complex were detected in the Alpine region. The geographical distribution of these evolutionary lineages coincided largely with several taxa (A.p. pallipes, A. berndhauseri, A.(p.) italicus) formerly defined on the basis of morphological characters. A low level of genetic variability was found within these lineages. For some populations, the combination of the two markers gave additional information about the likelihood of their natural or artificial origin. A hybrid zone was detected between A.p. pallipes and A. berndhauseri in the Lake Geneva area. The mosaic distribution of the five evolutionary lineages indicated that conservation efforts should be aimed at the level of local populations.
Phylogeography, intraspecific structure and sex‐biased dispersal of Dall’s porpoise, Phocoenoides dalli, revealed by mitochondrial and microsatellite DNA analyses
Authors: Escorza‐Treviño S. , Dizon A. E. 
Published: March 2003

AbstractMitochondrial DNA (mtDNA) control‐region sequences and microsatellite loci length polymorphisms were used to estimate phylogeographical patterns (historical patterns underlying contemporary distribution), intraspecific population structure and gender‐biased dispersal of Phocoenoides dalli dalli across its entire range. One‐hundred and thirteen animals from several geographical strata were sequenced over 379 bp of mtDNA, resulting in 58 mtDNA haplotypes. Analysis using FST values (based on haplotype frequencies) and ΦST values (based on frequencies and genetic distances between haplotypes) yielded statistically significant separation (bootstrap values P < 0.05) among most of the stocks currently used for management purposes. A minimum spanning network of haplotypes showed two very distinctive clusters, differentially occupied by western and eastern populations, with some common widespread haplotypes. This suggests some degree of phyletic radiation from west to east, superimposed on gene flow. Highly male‐biased migration was detected for several population comparisons. Nuclear microsatellite DNA markers (119 individuals and six loci) provided additional support for population subdivision and gender‐biased dispersal detected in the mtDNA sequences. Analysis using FST values (based on allelic frequencies) yielded statistically significant separation between some, but not all, populations distinguished by mtDNA analysis. RST values (based on frequencies of and genetic distance between alleles) showed no statistically significant subdivision. Again, highly male‐biased dispersal was detected for all population comparisons, suggesting, together with morphological and reproductive data, the existence of sexual selection. Our molecular results argue for nine distinct dalli‐type populations that should be treated as separate units for management purposes.
Is the Gibraltar Strait a barrier to gene flow for the bat Myotis myotis (Chiroptera: Vespertilionidae)?
Authors: Castella V. , Ruedi M. , Excoffier L. , Ibáñez C. , Arlettaz R. , Hausser J. 
Published: March 2003

AbstractBecause of their role in limiting gene flow, geographical barriers like mountains or seas often coincide with intraspecific genetic discontinuities. Although the Strait of Gibraltar represents such a potential barrier for both plants and animals, few studies have been conducted on its impact on gene flow. Here we test this effect on a bat species (Myotis myotis) which is apparently distributed on both sides of the strait. Six colonies of 20 Myotis myotis each were sampled in southern Spain and northern Morocco along a linear transect of 1350 km. Results based on six nuclear microsatellite loci reveal no significant population structure within regions, but a complete isolation between bats sampled on each side of the strait. Variability at 600 bp of a mitochondrial gene (cytochrome b) confirms the existence of two genetically distinct and perfectly segregating clades, which diverged several million years ago. Despite the narrowness of the Gibraltar Strait (14 km), these molecular data suggest that neither males, nor females from either region have ever reproduced on the opposite side of the strait. Comparisons of molecular divergence with bats from a closely related species (M. blythii) suggest that the North African clade is possibly a distinct taxon warranting full species rank. We provisionally refer to it as Myotis cf punicus Felten 1977, but a definitive systematic understanding of the whole Mouse‐eared bat species complex awaits further genetic sampling, especially in the Eastern Mediterranean areas.
Monitoring gene flow from transgenic sugar beet using cytoplasmic male‐sterile bait plants
Authors: Saeglitz Christiane , Pohl Matthias , Bartsch Detlef 
Published: March 2003

AbstractOne of the most discussed environmental effects associated with the use of transgenic plants is the flow of genes to plants in the environment. The flow of genes may occur through pollen since it is the reproductive system that is designed for gene movement. Pollen‐mediated gene escape is hard to control in mating plants. Pollen from a wind pollinator can move over distances of more than 1000 m. To investigate the efficiency of transgenic pollen movement under realistic environmental conditions, the use of bait plants might be an effective tool. In this study, cytoplasmic male‐sterile (CMS) sugar beets were tested with regard to their potential for monitoring transgene flow. As the pollen source, transgenic sugar beets were used that express recombinant DNA encoding viral (beet necrotic yellow vein virus) resistance, and antibiotic (kanamycin) and herbicide (glufosinate) tolerance genes. In a field trial, the effectiveness of a hemp (Cannabis sativa) stripe containment strategy was tested by measuring the frequency of pollinated CMS bait plants placed at different distances and directions from a transgenic pollen source. The results demonstrated the ineffectiveness of the containment strategy. Physiological and molecular tests confirmed the escape and production of transgenic offspring more than 200 m behind the hemp containment. Since absolute containment is unlikely to be effective, the CMS–bait plant detection system is a useful tool for other monitoring purposes.
Molecular genetic markers provide no evidence for reproductive isolation among retreat building phenotypes of the net‐spinning caddisfly Macrostemumcarolina
Authors: Plague G. R. , Mulvey M. , Glenn T. C. , Mcarthur J. V. 
Published: March 2003

AbstractLarvae of the stream‐dwelling, filter‐feeding caddisfly Macrostemumcarolina construct silken catchnets within protective retreats. In the Savannah River, M. carolina individuals make three different retreats, each with a distinct water entrance hole: (i) at the end of a silken tube; (ii) with a ≈180° silken backstop; and (iii) flush with the top of the retreat. To resolve whether these different retreats represent alternative behavioural phenotypes within a single panmictic population or fixed phenotypes within three genetically distinct populations or species, we compared the allele frequencies at three polymorphic nuclear loci (allozyme electrophoresis for Gpi, Mpi and Pgm) and the mitochondrial DNA (mtDNA) haplotype frequencies among individuals displaying the three retreat morphs. We also calculated pairwise exact tests of population differentiation using the allozyme and mtDNA allele frequencies. No significant genetic differentiation was detected among caddisflies exhibiting the different retreat morphs. Therefore, these morphs apparently represent a single panmictic population in the Savannah River. Consequently, additional study is required to assess whether this retreat polymorphism is a phenotypically plastic trait under conditional control, or is mediated by alternative alleles at a Mendelian gene or genes (or a combination of the two).
Divergence between two Antarctic species of the ciliate Euplotes, E. focardii and E. nobilii, in the expression of heat‐shock protein 70 genes
Authors: La Terza A. , Papa G. , Miceli C. , Luporini P. 
Published: March 2003

AbstractMost organisms oppose many environmental stresses by rapidly enhancing synthesis of the highly conserved Hsp70 family of heat‐shock proteins. Two ciliates which are endemic in Antarctic coastal seawater, Euplotes focardii and E. nobilii, and behave as psychrophile and psychrotroph micro‐organisms, respectively, revealed a divergence in the capacity to respond to thermal stress with an activation of the transcription of their hsp70 genes. In both species, these genes were shown to be represented by thousands of copies in the cell’s somatic functional nucleus (macronucleus). However, while a strong transcriptional activity of hsp70 genes was induced in E. nobilii cells transferred from 4 to 20 °C, a much smaller increase was revealed in heat‐shocked cells of E. focardii. These findings suggest a closer adaptation to the stably cold Antarctic waters in the genetic response of E. focardii to thermal stress.
Pollen pool heterogeneity in shortleaf pine, Pinus echinata Mill.
Authors: Dyer R. J. , Sork V. L. 
Published: March 2003

AbstractPollen is the dominant vector of gamete exchange for most temperate tree species. Because pollen movement influences the creation, maintenance and erosion of genetic structure in adult populations, it is important to understand what factors influence the process of pollen movement. Isolation by distance in pollen donor populations can create highly structured pollen polls by increased sampling of local fathers. Extrinsic factors, such as the intervening vegetative structure and local pollen donor densities, can also influence the genetic composition of local pollen pools. Using paternally inherited chloroplast microsatellite markers, we examined the structure and diversity of pollen pools in Pinus echinata Mill. in southern Missouri, USA. Our analysis is based on a multivariate amova analysis of stands (≈ 1 ha; six per region) nested within regions (≈ 800 ha; four each). Significant multilocus structure of the pollen pool within regions (φSR = 0.095), but not among regions (φRT = 0.010), indicates that pollen movement is relatively restricted. Furthermore, the significant correlation between pairwise genetic and physical distances (Mantel correlation; ρ = 0.32) provided support for the isolation by distance hypothesis. Our results indicated that availability of pollen donors did not affect diversity of the pollen pool, measured by the number of unique multilocus genotypes at each stand. However, pollen pool diversity was negatively associated with vegetative structure, measured as total forest tree density. Our findings indicated that on‐going pollen movement within continuous forest is relatively restricted as a result of both isolation by distance and vegetative structure.
Genetic structure of brown trout (Salmo trutta, L.) populations from south‐western France: data from mitochondrial control region variability
Authors: Aurelle D. , Berrebi P. 
Published: March 2003

AbstractThe genetic relationships between several French Atlantic populations of brown trout were analysed using polymerase chain reaction–single‐strand conformation polymorphism and sequencing of two parts of the mitochondrial control region. Ten mitochondrial haplotypes were identified, separated by a small number of mutations. The distribution of these haplotypes confirmed our hypothesis of the existence of two genetically well‐differentiated groups of populations in this area, which has already been suggested using nuclear markers. Nuclear and mitochondrial markers, however, show different patterns of genetic differentiation: some populations which belong to one group according to allozyme results appear to be part of the other when using mitochondrial DNA. The origin of these different forms is discussed; they seem to belong to the Atlantic grouping. Nevertheless, the hypothesis of an ancestral and a modern form suggested for northern populations does not appear valid in this particular case.
Insertion polymorphism of retrotransposable elements in populations of the insular, endemic species Drosophila madeirensis
Authors: Lepetit D. , Brehm A. , Fouillet P. , Biémont C. 
Published: March 2003

AbstractThe insertion site numbers of the retrotransposable elements (TE) 412, gypsy and bilbo were determined in individuals of five distinct natural populations of the endemic species Drosophila madeirensis from the island of Madeira. The TE distributions were compared to those of the paleartic, widespread and phylogenetically closely related species, D. subobscura. In situ hybridization and Southern blots showed that in D. madeirensis the number of insertion sites ranged between 10 and 15, three and six, and 35 and 42 for elements 412, gypsy and bilbo, respectively. The corresponding values for D. subobscura were similar. Two of these elements, 412 and gypsy, had very few insertions in the heterochromatin, unlike bilbo, which displayed a high heterochromatic insertion number. The Southern band polymorphism was very high, leading to within‐population variation of 97.2%, whatever the population and the TE concerned. Using the polymorphic TE insertion sites as markers to analyse population structure by amova, adapted for RAPD (Randomly Amplified Polymorphic DNA) data, we found small but significant genetic differences between the populations on Madeira. This slight differentiation, coupled with similar copy numbers for each TE between populations, suggests that the D. madeirensis species consists of a single, only slightly subdivided population. These data also show that insular populations and endemic species of Drosophila can have as many copies of TEs as more widespread species.
Noninvasive molecular tracking of colonizing wolf (Canis lupus) packs in the western Italian Alps
Authors: Lucchini V. , Fabbri E. , Marucco F. , Ricci S. , Boitani L. , Randi E. 
Published: March 2003

AbstractWe used noninvasive methods to obtain genetic and demographic data on the wolf packs (Canis lupus), which are now recolonizing the Alps, a century after their eradication. DNA samples, extracted from presumed wolf scats collected in the western Italian Alps (Piemonte), were genotyped to determine species and sex by sequencing parts of the mitochondrial DNA (mtDNA) control‐region and ZFX/ZFY genes. Individual genotypes were identified by multilocus microsatellite analyses using a multiple tubes polymerase chain reaction (PCR). The performance of the laboratory protocols was affected by the age of samples. The quality of excremental DNA extracts was higher in samples freshly collected on snow in winter than in samples that were older or collected during summer. Preliminary mtDNA screening of all samples allowed species identification and was a good predictor of further PCR performances. Wolf, and not prey, DNA targets were preferentially amplified. Allelic dropout occurred more frequently than false alleles, but the probability of false homozygote determinations was always < 0.001. A panel of six to nine microsatellites would allow identification of individual wolf genotypes, also whether related, with a probability of identity of < 0.015. Genealogical relationships among individuals could be determined reliably if the number of candidate parents was 6–8, and most of them had been sampled and correctly genotyped. Genetic data indicate that colonizing Alpine wolves originate exclusively from the Italian source population and retain a high proportion of its genetic diversity. Spatial and temporal locations of individual genotypes, and kinship analyses, suggest that two distinct packs of closely related wolves, plus some unrelated individuals, ranged in the study areas. This is in agreement with field observations.
Phylogeography of the common ivy (Hedera sp.) in Europe: genetic differentiation through space and time
Authors: Grivet D. , Petit R. J. 
Published: March 2003

AbstractWe studied the phylogeography of ivy (Hedera sp.), a liana widespread in Europe, throughout its natural range. The populations sampled belong to four closely related species differing by ploidy levels and morphological characters. Chloroplast (cp) markers were used and 13 haplotypes were detected, usually shared across species, contrary to ribosomal internal transcribed spacer (ITS) variants. We demonstrated the existence of a strong overall cpDNA phylogeographical structure. Several methods of data analysis were conducted to describe how this structure and the genetic diversity change through space and time. Southern populations, especially those from Spain, are the most divergent. Pairwise estimates of differentiation point to isolation by distance, and the existence of a latitudinal gradient of divergence was demonstrated using a regression procedure. Similarly, latitudinal differences in haplotype richness and diversity exist, as shown by population permutations (‘differentiation through space’). Finally, we measured differentiation by taking into account successive levels of divergence between haplotypes (‘differentiation through time’). Genetic differentiation turns out to be much greater when differences between closely related haplotypes are not considered. Further, these results indicate that the phylogeographical structure is essentially due to the relative distribution of the most similar haplotypes. Diversity decreases from south to north, whereas haplotype frequencies change longitudinally. It appears that Hedera survived in Spanish and Balkan refugia during the last ice age. A third refugium must have been present in the Alps or in Italy. During the northward expansion, the decrease in overall diversity was attenuated by some mixing of lineages at intermediate latitudes, resulting in comparatively higher levels of differentiation in the south.
Recent changes in phenotype and patterns of host specialization in Wolbachia bacteria
Authors: Jiggins Francis M. , Bentley Joanna K. , Majerus Michael E. N. , Hurst Gregory D. D. 
Published: March 2003

Abstract Wolbachia are a genus of bacterial symbionts that are known to manipulate the reproduction of their arthropod hosts, both by distorting the host sex ratio and by inducing cytoplasmic incompatibility. Previous work has suggested that some Wolbachia clades specialize in particular host taxa, but others are diverse. Furthermore, the frequency with which related strains change in phenotype is unknown. We have examined these issues for Wolbachia bacteria from Acraea butterflies, where different interactions are known in different host species. We found that bacteria from Acraea butterflies mostly cluster together in several different clades on the bacterial phylogeny, implying specialization of particular strains on these host taxa. We also observed that bacterial strains with different phenotypic effects on their hosts commonly shared identical gene sequences at two different loci. This suggests both that the phenotypes of the strains have changed recently between sex ratio distortion and cytoplasmic incompatibility, and that host specialization is not related to the bacterial phenotype, as suggested from previous data. We also analysed published data from other arthropod taxa, and found that the Wolbachia infections of the majority of arthropod genera tend to cluster together on the bacterial phylogeny. Therefore, we conclude that Wolbachia is most likely to move horizontally between closely related hosts, perhaps because of a combination of shared vectors for transmission and physiological specialization of the bacteria on those hosts.
Communities and populations of sebacinoid basidiomycetes associated with the achlorophyllous orchid Neottia nidus‐avis (L.) L.C.M. Rich. and neighbouring tree ectomycorrhizae
Authors: Selosse Marc‐André , WEIß Michael , Jany Jean‐Luc , Tillier Annie 
Published: March 2003

AbstractSeveral achlorophyllous orchids associate with ectomycorrhizal hymenomycetes deriving carbon from surrounding trees for the plant. However, this has not been shown for achlorophyllous orchids associating with species of Rhizoctonia, a complex of basal lineages of hymenomycetes that are the most common orchid partners. We analysed Neottia nidus‐avis, an achlorophyllous orchid symbiotic with a Rhizoctonia, to identify its symbionts by internal transcribed spacer (ITS) sequencing. Analysis of 61 root systems from 23 French populations showed that N. nidus‐avis associates highly specifically with a group of species of Sebacinaceae. Their diversity emphasizes the need for further investigations in the Sebacinaceae systematics. Sebacinoid ITS sequences were often identical within orchid populations and a trend to regional variation in symbionts was observed. Using ITS and intergenic spacer (IGS) polymorphism, we showed that each root system harboured a single species, but that several genets colonized it. However, no polymorphism of these markers was found among portions of each root: this is consistent with the putative mode of entry of the fungus, i.e. from the rhizome into roots but not repeatedly from the soil. In addition, ectomycorrhizae were always found within the N. nidus‐avis root systems: 120 of the 144 ectomycorrhizae typed by ITS sequencing were colonized by a sebacinoid fungus identical in ITS sequence to the respective orchid symbiont (even for the IGS polymorphism in some cases). Because sebacinoids were demonstrated recently to be ectomycorrhizal, the orchid is likely to derive its resources from surrounding trees, a mycorrhizal cheating strategy similar to other myco‐heterotrophic plants studied to date.