bluuebunny/crossref_metadata_2025_split huggingface dataset:
Maternal inheritance of a chloroplast microsatellite marker in controlled hybrids between Fraxinus excelsior and Fraxinus angustifolia
Authors: Morand‐Prieur M. E. , Vedel F. , Raquin C. , Brachet S. , Sihachakr D. , Frascaria‐Lacoste N. 
Published: March 2003

AbstractRestriction fragment length polymorphism, polymerase chain reaction–restriction fragment length polymorphism and simple sequence repeat (SSR or microsatellites) analyses were performed to detect chloroplast DNA polymorphisms between two ash species, Fraxinus excelsior and F.angustifolia. Only one SSR locus was found to be polymorphic, confirming the very close relatedness of these species. Inheritance of this marker was studied in hybrids obtained from controlled crosses between the two tree species. Results indicated, for the first time in Oleaceae, that chloroplasts are maternally inherited. This chloroplast SSR marker is now used concomitantly with nuclear markers to analyse ash populations in sympatric areas.
Fine‐scale population structure and dispersal inBiomphalaria glabrata, the intermediate snail host ofSchistosoma mansoni, in Venezuela
Authors: Mavárez J. , Amarista M. , Pointier J.‐P. , Jarne P. 
Published: March 2003

AbstractBiomphalaria glabratais the main intermediate host ofSchistosoma mansoniin America and one of the most intensely studied species of freshwater snails, yet very little is known about its population biology. Here, we used seven highly polymorphic microsatellite loci to analyse genetic diversity in the Valencia lake basin, which represents the core of the endemic area for schistosomiasis in Venezuela. Populations were sampled at short spatial scale (a few kilometres), both inside the lake and in ponds or rivers near the lake. Our results indicate thatB. glabrataessentially cross‐fertilizes, with little variation in selfing rates among populations. Our markers detected considerable genetic variation, with an average heterozygosity of 0.60. More diversity per population was found within than outside the lake, suggesting an influence of connectivity among populations on the levels of genetic diversity. A marked population structure was detected and lake populations were less structured than other populations. Most individuals were assigned to their population of origin using an assignment test. No strong demographic signal (e.g. bottleneck) was detected, though lake populations are likely to experience bottlenecks more frequently than the other populations analysed. Differences in gene flow therefore seem to play an important role in population differentiation and in the restoring of genetic diversity in demographically unstable populations.
Variation at the major histocompatibility complex in Savannah sparrows
Authors: Freeman‐Gallant Corey R. , Johnson Elizabeth M. , Saponara Fiorella , Stanger Matthew 
Published: March 2003

AbstractThe class I and class II genes of the major histocompatibility complex (Mhc) encode dimeric glycoproteins responsible for eliciting the adaptive immune response of vertebrates. Recent work with birds suggests that the number, size, and arrangement of these genes can differ markedly across species, although the extent of this variation, and its causes and consequences, are poorly understood. We have used a 157‐base‐pair (bp) portion of the second exon of a class IIBgene to probe theMhcin a free‐living population of Savannah sparrows (Passerculus sandwichensis). Segregation analysis ofMhcbands suggests that class IIBgenes can be found in two independently assorting clusters, as previously described for domestic chickens (Gallus gallus) and ring‐necked pheasants (Phasianus colchicus) but unlike gene organization in mammals. TheMhcin Savannah sparrows appears large (with many class IIBgenes) and variable; we found 42 unique genotypes among 48 adults breeding on Kent Island, New Brunswick, Canada in 1995. Savannah sparrows are long‐distance migrants, and these results support recent predictions that migratory birds should show higher levels ofMhcpolymorphism and/or a greater number of genes than sedentary species. Savannah sparrows are also socially polygynous with high levels of extra‐pair paternity, suggesting that a history of sexual selection might also influence the size and/or structure of the avianMhc.
Population structure of plaice (Pleuronectes platessa L.) in northern Europe: microsatellites revealed large‐scale spatial and temporal homogeneity
Authors: Hoarau G. , Rijnsdorp A. D. , Van Der Veer H. W. , Stam W. T. , Olsen J. L. 
Published: March 2003

AbstractPhilopatry to spawning grounds combined with well‐known migratory patterns in the flatfish Pleuronectes platessa (plaice) has led to the hypothesis that regional populations may reflect relatively discrete, genetic stocks. Using six microsatellite loci we genotyped 240 adult individuals collected from locations in Norway, the Faeroe plateau, the Irish Sea, the Femer Baelt, Denmark, and the southern North Sea, and 240 0‐class juveniles collected from five nursery‐ground locations in Iceland, northwest Scotland, two sites in the Wadden Sea, and the Bay of Vilaine in Southern Brittany. The mean number of alleles/locus ranged from 5.3 to 20.4, with a mean of 13.9. Expected heterozygosity was uniformly high across all locations (multilocus Hexp = 0.744 ± 0.02). Pairwise comparisons of θ among all 11 locations revealed significant differentiation between Iceland and all other locations (θ = 0.0290*** to 0.0456***), which is consistent with the deep–water barrier to dispersal in plaice. In contrast, no significant differentiation was found among any of the remaining continental‐shelf sampling locations. This suggests that regional stocks are themselves composed of several genetic stocks under a model of panmixia which persists even to the spawning grounds. The presence of significant heterozygote deficiencies at all locations (not due to null alleles) suggests a temporal Wahlund effect yet the absence of significant population differentiation among continental shelf localities makes this explanation alone, difficult to reconcile. Sampling of eggs at the spawning grounds will be required to resolve this issue. Causes of the mismatch between genetic and geographical stocks is discussed in the context of high gene flow.
A genetic assessment of parentage in a natural population of dollar sunfish (Lepomis marginatus) based on microsatellite markers
Authors: MacKiewicz M. , Fletcher D. E. , Wilkins S. D. , Dewoody J. A. , Avise J. C. 
Published: March 2003

AbstractWe employ microsatellite markers to assess mating tactics in Lepomis marginatus. Genetic assignments for 1015 progeny in 23 nests indicate that about 95% of the offspring were sired by their respective nest‐guardians, a finding consistent with the apparent absence of a brood parasitic morphotype in this species. Allopaternal care was documented in two nests, one resulting from a nest takeover, the other from cuckoldry by an adjoining nest‐tender. Clustered de novo mutations also were identified. About 2.5 females (range 1–7) contributed to the offspring pool within a typical nest. Results are compared to those for other Lepomis species.
Phylogeographic analysis of a recent radiation ofEnallagmadamselflies (Odonata: Coenagrionidae)
Authors: Turgeon J. , McPeek M. A. 
Published: March 2003

AbstractA phylogenetic hypothesis revealed two recent radiations among species ofEnallagmadamselflies, and extensive ecological work suggests that both adaptive and nonadaptive processes are involved in these radiations. We analysed the geographical pattern of genetic variability at 868 bp of mitochondrial DNA (mtDNA) among 283 individuals of 5 species displaying little ecological differentiation to identify the ancestral lineage, support their independent evolutionary trajectories and identify historical events and the underlying mechanism for one of these radiations. Nested clade analysis results clearly support a past event of range fragmentation inE. hageni. These Atlantic and Continentalhageniraces experienced distinct dispersal histories and still maintain nearly nonoverlapping ranges All four other species derive from the Continentalhageni. Whereas three species endemic to the Atlantic coastal plain show little genetic variation,E. ebriumshared several haplotypes with the Continentalhageni. Contrasting levels of genetic differentiation betweenE. hageniandE. ebriumin geographical areas associated with distinct events ofE. hageni's recent history support the recent origin of this species. Altogether, our results are compatible with a process of radiation via divergence in mate recognition systems within the Continentalhagenirace following secondary contacts between putative refugial races.
Polyploidy, phylogeography and Pleistocene refugia of the rockfern Asplenium ceterach: evidence from chloroplast DNA
Authors: Trewick S. A. , Morgan‐Richards M. , Russell S. J. , Henderson S. , Rumsey F. J. , Pintér I. , Barrett J. A. , Gibby M. , Vogel J. C. 
Published: March 2003

AbstractChloroplast DNA sequences were obtained from 331 Asplenium ceterach plants representing 143 populations from throughout the range of the complex in Europe, plus outlying sites in North Africa and the near East. We identified nine distinct haplotypes from a 900 bp fragment of trnL‐trnF gene. Tetraploid populations were encountered throughout Europe and further afield, whereas diploid populations were scarcer and predominated in the Pannonian‐Balkan region. Hexaploids were encountered only in southern Mediterranean populations. Four haplotypes were found among diploid populations of the Pannonian‐Balkans indicating that this region formed a northern Pleistocene refugium. A separate polyploid complex centred on Greece, comprises diploid, tetraploid and hexaploid populations with two endemic haplotypes and suggests long‐term persistence of populations in the southern Mediterranean. Three chloroplast DNA (cpDNA) haplotypes were common among tetraploids in Spain and Italy, with diversity reducing northwards suggesting expansion from the south after the Pleistocene. Our cpDNA and ploidy data indicate at least six independent origins of polyploids.
Loss of genetic diversity in sea otters (Enhydra lutris) associated with the fur trade of the 18th and 19th centuries
Authors: Larson Shawn , Jameson Ronald , Etnier Michael , Fleming Melissa , Bentzen Paul 
Published: March 2003

AbstractSea otter (Enhydra lutris) populations experienced widespread reduction and extirpation due to the fur trade of the 18th and 19th centuries. We examined genetic variation within four microsatellite markers and the mitochondrial DNA (mtDNA) d‐loop in one prefur trade population and compared it to five modern populations to determine potential losses in genetic variation. While mtDNA sequence variability was low within both modern and extinct populations, analysis of microsatellite allelic data revealed that the prefur trade population had significantly more variation than all the extant sea otter populations. Reduced genetic variation may lead to inbreeding depression and we believe sea otter populations should be closely monitored for potential associated negative effects.
Spatial genetic structure and clonal diversity of island populations of lady's slipper (Cypripedium calceolus) from the Biebrza National Park (northeast Poland)
Authors: Brzosko E. , Wróblewska A. , Ratkiewicz M. 
Published: March 2003

AbstractThree populations of the rare and endangered plant speciesCypripedium calceoluswere included in a study of genetic diversity and spatial genetic structure in the Biebrza National Park, northeast Poland. Analysis of 11 allozyme loci indicate that the populations of this species contained high genetic variability (P = 45.5%,A= 1.73). On the other hand, the genetic differentiation (FST = 0.014,P< 0.05) amongC. calceoluspopulations was very low when compared to other species with similar life history characteristics. The observed high rate of gene flow (Nm = 18) may suggest that the populations studied derived from each other in the recent past. Five polymorphic allozyme markers identified 109 multilocus genotypes in three populations and the majority of them (67%) were population‐specific. One of the populations studied, characterized by particularly extensive vegetative reproduction, showed the lowest clonal diversity (G/N = 0.15) and heterozygosity (HO = 0.111) values and the highestFIS(0.380), when compared to other two populations (G/N = 0.26–0.27,HO= 0.166–178,FIS = 0.024–0.055). This may indicate that clonal reproduction has an important influence on the genetic structure ofC. calceoluspopulations. The longevity of genets, the out‐crossing breeding system and the presence of recruitment from seeds are factors maintaining genetic diversity inC. calceolus.
Molecular diversity of arbuscular mycorrhizal fungi and patterns of host association over time and space in a tropical forest
Authors: Husband R. , Herre E. A. , Turner S. L. , Gallery R. , Young J. P. W. 
Published: March 2003

AbstractWe have used molecular techniques to investigate the diversity and distribution of the arbuscular mycorrhizal (AM) fungi colonizing tree seedling roots in the tropical forest on Barro Colorado Island (BCI), Republic of Panama. In the first year, we sampled newly emergent seedlings of the understory treelet Faramea occidentalis and the canopy emergent Tetragastris panamensis, from mixed seedling carpets at each of two sites. The following year we sampled surviving seedlings from these cohorts. The roots of 48 plants were analysed using AM fungal‐specific primers to amplify and clone partial small subunit (SSU) ribosomal RNA gene sequences. Over 1300 clones were screened for random fragment length polymorphism (RFLP) variation and 7% of these were sequenced. Compared with AM fungal communities sampled from temperate habitats using the same method, the overall diversity was high, with a total of 30 AM fungal types identified. Seventeen of these types have not been recorded previously, with the remainder being similar to types reported from temperate habitats. The tropical mycorrhizal population showed significant spatial heterogeneity and nonrandom associations with the different hosts. Moreover there was a strong shift in the mycorrhizal communities over time. AM fungal types that were dominant in the newly germinated seedlings were almost entirely replaced by previously rare types in the surviving seedlings the following year. The high diversity and huge variation detected across time points, sites and hosts, implies that the AM fungal types are ecologically distinct and thus may have the potential to influence recruitment and host composition in tropical forests.
Y chromosome conserved anchored tagged sequences (YCATS) for the analysis of mammalian male‐specific DNA
Authors: Hellborg Linda , Ellegren Hans 
Published: March 2003

AbstractY chromosome haplotyping based on microsatellites or single nucleotide polymorphisms has recently proven to be a powerful approach for evolutionary studies of human populations, and also holds great promise for the studies of wild species. However, the use of the approach is hampered in most natural populations by the lack of Y chromosome markers and sequence information. Here, we report the large‐scale development of Y chromosome conserved anchor tagged sequence (YCATS) markers in mammals by a polymerase chain reaction screening approach. Exonic primers flanking 48 different introns of Y‐linked genes were developed based on human and mouse sequences, and screened on a set of 20 different mammals. On average about 10 introns were amplified for each species and a total of 100 kb of Y chromosome sequence were obtained. Intron size in humans was a reasonable predictor of intron size in other mammals (r2 = 0.45) and there was a negative correlation between human fragment size and amplification success. We discuss a number of factors affecting the possibility of developing conserved Y chromosome markers, including fast evolution of Y chromosome sequences due to male‐biased mutation and adaptive evolution of male‐specific genes, dynamic evolution of the Y chromosome due to being a nonrecombining unit, and homology with X chromosome sequences.
Phylogeny and ecological radiation of New World thistles (Cirsium, Cardueae – Compositae) based on ITS and ETS rDNA sequence data
Authors: Kelch Dean G. , Baldwin Bruce G. 
Published: March 2003

AbstractSequence data from a portion of the external transcribed spacer (ETS) and internal transcribed spacers (ITS‐1 and ITS‐2) of 18S‐26S nuclear ribosomal DNA were used to resolve historical biogeography and ecology of true thistles (Cirsium, Cardueae, Compositae) in the New World. The 650 base‐pair, 3′ portion of the ETS examined here showed a level of variation across taxa similar to that of the ITS sequences included. A maximum‐likelihood tree based on combined ETS and ITS sequences leads us to suggest that the New World species of true thistles constitute a major lineage, which in turn comprises several smaller lineages. A western North American lineage shows weak quartet‐puzzling support, but includes a well‐supported lineage of species endemic to the California Floristic Province. Comparisons of this Californian lineage with other neoendemic angiosperm groups of the region show that the CalifornianCirsiumlineage exhibits unusually high ecological diversity for a group displaying such low levels of rDNA sequence divergence across taxa. Similarly low levels of sequence divergence were found throughout the New WorldCirsiumlineage. These results indicate either thatCirsiumunderwent a rapid ecological radiation in North America, or that rDNA evolution in North AmericanCirsiumhas been highly conservative.
Conservation genetics of the fisher (Martes pennanti) based on mitochondrial DNA sequencing
Authors: Drew R. E. , Hallett J. G. , Aubry K. B. , Cullings K. W. , Koepf S. M. , Zielinski W. J. 
Published: March 2003

AbstractTranslocation of animals to re‐establish extirpated populations or to maintain declining ones has often been carried out without genetic information on source or target populations, or adequate consideration of the potential effects of mixing genetic stocks. We consider the conservation status of the fisher (Martes pennanti) and evaluate the potential genetic consequences of past and future translocations on this medium‐sized carnivore by examining population variation in mitochondrial control‐region sequences. We sampled populations throughout the fisher's range in North America including five populations unaffected by translocations and two western populations that had received long‐distance translocations. Twelve haplotypes showed little sequence divergence. Haplotype frequencies differed significantly among subspecies and between populations within subspecies. Analysis of molecular variance (amova) and neighbour‐joining analyses of haplotype relationships revealed population subdivision similar to current subspecies designations, but which may reflect an isolation‐by‐distance pattern. Populations in Oregon and in Montana and Idaho received several translocations and each showed greater similarity to the populations where translocations originated than to adjacent populations. Additional sequences obtained from museum specimens collected prior to any translocations suggest historical gene flow among populations in British Columbia, Washington, Oregon, and California. Anthropogenic impacts in that region have greatly reduced and isolated extant populations in Oregon and California. Future translocations may be necessary to recover populations in Washington and portions of Oregon and California; our results indicate that British Columbia would be the most appropriate source population.
The trans‐activation domain of the sporulation response regulator Spo0A revealed by X‐ray crystallography
Authors: Lewis Richard J. , Krzywda Szymon , Brannigan James A. , Turkenburg Johan P. , Muchová Katarína , Dodson Eleanor J. , Barák Imrich , Wilkinson Anthony J. 
Published: March 2003

Sporulation in Bacillus involves the induction of scores of genes in a temporally and spatially co‐ordinated programme of cell development. Its initiation is under the control of an expanded two‐component signal transduction system termed a phosphorelay. The master control element in the decision to sporulate is the response regulator, Spo0A, which comprises a receiver or phosphoacceptor domain and an effector or transcription activation domain. The receiver domain of Spo0A shares sequence similarity with numerous response regulators, and its structure has been determined in phosphorylated and unphosphorylated forms. However, the effector domain (C‐Spo0A) has no detectable sequence similarity to any other protein, and this lack of structural information is an obstacle to understanding how DNA binding and transcription activation are controlled by phosphorylation in Spo0A. Here, we report the crystal structure of C‐Spo0A from Bacillus stearothermophilus revealing a single α‐helical domain comprising six α‐helices in an unprecedented fold. The structure contains a helix–turn–helix as part of a three α‐helical bundle reminiscent of the catabolite gene activator protein (CAP), suggesting a mechanism for DNA binding. The residues implicated in forming the σA‐activating region clearly cluster in a flexible segment of the polypeptide on the opposite side of the structure from that predicted to interact with DNA. The structural results are discussed in the context of the rich array of existing mutational data.
Four genes are required for the system II cytochrome c biogenesis pathway in Bordetella pertussis, a unique bacterial model
Authors: Beckett Caroline S. , Loughman Jennifer A. , Karberg Katherine A. , Donato Gina M. , Goldman William E. , Kranz Robert G. 
Published: March 2003

Unlike other cytochromes, c‐type cytochromes have two covalent bonds formed between the two vinyl groups of haem and two cysteines of the protein. This haem ligation requires specific assembly proteins in prokaryotes or eukaryotic mitochondria and chloroplasts. Here, it is shown that Bordetella pertussis is an excellent bacterial model for the widespread system II cytochrome c synthesis pathway. Mutations in four different genes (ccsA, ccsB, ccsX and dipZ) result in B. pertussis strains unable to synthesize any of at least seven c‐type cytochromes. Using a cytochrome c4:alkaline phosphatase fusion protein as a bifunctional reporter, it was demonstrated that the B. pertussis wild‐type and mutant strains secrete an active alkaline phosphatase fusion protein. However, unlike the wild type, all four mutants are unable to attach haem covalently, resulting in a degraded N‐terminal apocytochrome c4 component. Thus, apocytochrome c secretion is normal in each of the four mutants, but all are defective in a periplasmic assembly step (or export of haem). CcsX is related to thioredoxins, which possess a conserved CysXxxXxxCys motif. Using phoA gene fusions as reporters, CcsX was proven to be a periplasmic thioredoxin‐like protein. Both the B. pertussis dipZ (i.e. dsbD) and ccsX mutants are corrected for their assembly defects by the thiol‐reducing compounds, dithiothreitol and 2‐mercaptoethanesulphonic acid. These results indicate that DipZ and CcsX are required for the periplasmic reduction of the cysteines of apocytochromes c before ligation. In contrast, the ccsA and ccsB mutants are not corrected by exogenous reducing agents, suggesting that CcsA and CcsB are required for the haem ligation step itself in the periplasm (or export of haem to the periplasm). Related to this suggestion, the topology of CcsB was determined experimentally, demonstrating that CcsB has four transmembrane domains and a large 435‐amino‐acid periplasmic region.