bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolutionary history of the land snail Helix aspersa in the Western Mediterranean: preliminary results inferred from mitochondrial DNA sequences
Authors: Guiller A. , Coutellec‐Vreto M. A. , Madec L. , Deunff J. 
Published: March 2003

AbstractIntraspecific phylogeographic methods provide a means of examining the history of genetic exchange among populations. As part of a study of the history of Helixaspersa in the Western Mediterranean, we performed a phylogenetic analysis based on partial sequences of the mitochondrial large ribosomal subunit (16S) gene. Our samples include 31 H. a. aspersa populations from North Africa previously investigated for anatomical and biochemical characters. To clarify subspecific relationships, three individuals of the subspecies H. a. maxima were also studied. The molecular phylogeny inferred agrees largely with previous results, in splitting H. a. aspersa haplotypes into an eastern and a western group. H. a. maxima haplotypes form a third lineage arising before the H. a.aspersa groups. Divergence times estimated between the lineages suggest that dispersal during Pleistocene glaciation and vicariance events due to Pliocene geological changes in the western Mediterranean may both have played a significant part in the establishment of the present range of H. aspersa.
Swarm‐founding in the polistine wasps: the importance of finding many microsatellite loci in studies of adaptation
Authors: Henshaw M. T. , Strassmann J. E. , Queller D. C. 
Published: March 2003

AbstractWe developed 52 microsatellite loci for the wasp,Polybioides tabidus, for the purpose of studying the evolution and inclusive fitness consequences of swarm‐founding. The large number of loci is important for three reasons that may apply to many other systems. Heterozygosity was low in our target species, yet we found enough polymorphic loci for accurate kinship studies in this species. Many monomorphic loci were polymorphic in other polistine wasps, making comparative studies possible. Finally, enough loci amplified over a broad range of species to add a historical dimension. We sequenced six loci in other polistine wasps and used the flanking sequences to construct a phylogeny. Based on this phylogeny, we infer that swarm‐founding has evolved independently three times in the polistine wasps.
Did the Pleistocene glaciations promote divergence? Tests of explicit refugial models in montane grasshopprers
Authors: Knowles L. Lacey 
Published: March 2003

AbstractThere is a long‐standing debate over whether or not the Pleistocene glaciations promoted speciation. While some models predict that extensive mixing of populations during interglacial expansion would have inhibited divergence, others postulate that divergence among allopatric glacial refuges or founder events during recolonization of previously glaciated areas would have promoted differentiation. Using a combination of traditional and coalescent based population genetic approaches, this study finds that the glaciations did not inhibit divergence among populations of the grasshopper Melanoplus oregonensis. Instead, drift associated with recolonization of previously glaciated areas, as well as divergence among multiple allopatric glacial refugia, have both contributed to differentiation in this montane grasshopper from the ‘sky islands’ of the northern Rocky Mountains. Significant population structure was detected by phylogenetic and FST analyses, including significant FST values among individual pairs of sky‐island populations. In addition to clustering of haplotypes within populations, there is some evidence of regional phylogeographic structure, although none of the ‘regional groups’ form a monophyletic clade and there is a lack of concordance between the genealogical and geographical positions of some haplotypes. However, coalescent simulations confirm there is significant regional phylogeographic structure that most likely reflects divergence among multiple ancestral refugial populations, and indicate that it is very unlikely that the observed gene tree could have been produced by the fragmentation of a single widespread ancestral population. Thus, rather than inhibiting differentiation, the glaciations appear to have promoted population divergence in M. oregonensis, suggesting that they may have contributed to the radiation of Melanoplus species during the Pleistocene.
Founder effect in an island population of bighorn sheep
Authors: Hedrick P. W. , Gutierrez‐Espeleta G. A. , Lee R. N. 
Published: March 2003

AbstractThe Tiburon Island population of desert bighorn sheep has increased in size from 20 founders in 1975 to approximately 650 in 1999. This population is now the only population being used as the source stock for transplantations throughout northern Mexico. To evaluate the genetic variation in this population, we examined 10 microsatellite loci and a major histocompatibility complex (MHC) locus. The genetic variation was significantly less than found in other populations of the same subspecies in Arizona. Using a model that takes into account the effects of genetic drift on genetic distance, most of the genetic distance observed between the Tiburon population and Arizona samples could be explained. Because of the low genetic variation found in the Tiburon population, it is suggested that the Tiburon population should be supplemented with additional unrelated animals or that the transplant populations should be supplemented with unrelated animals.
Phylogenetic analyses of Caulerpa taxifolia (Chlorophyta) and of its associated bacterial microflora provide clues to the origin of the Mediterranean introduction
Authors: Meusnier I. , Olsen J. L. , Stam W. T. , Destombe C. , Valero M. 
Published: March 2003

AbstractThe accidental introduction of Caulerpa taxifolia into the Mediterranean is no longer under dispute. What has eluded researchers until now, is definitive evidence for the original, biogeographical source population. Here we present two independent lines of evidence that support an Australian origin for the Mediterranean populations of C. taxifolia. First, we reanalysed algal rDNA‐internal transcribed spacer (rDNA‐ITS) sequences, combining previously published sequences from different studies with 22 new sequences. The ITS sequence comparison showed that the Australian sample is the sister group of the Mediterranean–aquarium clade. Second, cloned bacterial 16S rDNA gene sequences were analysed from the associated microflora of C. taxifolia collected from Australia, Tahiti, the Philippines and the Mediterranean. Five bacterial lineages were identified, of which three were dominant. Alpha Proteobacteria were the most abundant and were found in all samples. In contrast, members of the beta Proteobacterial line and Cytophaga‐Flexibacter‐Bacteroides line (CFB) were mainly associated with Mediterranean and Australian samples. Frequency distributions of the five bacterial lineages were significantly different among biogeographical locations. Phylogenetic analyses of the 54 bacterial sequences derived from the four C. taxifolia individuals resulted in a well‐resolved tree with high bootstrap support. The topologies of the beta Proteobacteria and CFB mirror the geographical sources of their algal hosts. Bacterial–algal associations provide an identification tool that may have wide application for the detection of marine invasions.
Mode of reproduction and amplified fragment length polymorphism variation in purple needlegrass (Nassella pulchra): utilization of natural germplasm sources
Authors: Larson S. R. , Cartier E. , Mccracken C. L. , Dyer D. 
Published: March 2003

AbstractA dominant plant of the California grasslands, purple needlegrass [Nassella pulchra (Hitchc.) Barkworth] is an important revegetation species in its native range. The amplified fragment length polymorphism (AFLP) method was used to elucidate mode of reproduction and nucleotide variation among 11 natural populations and three selected natural germplasm releases of N. pulchra. A total of 12 co‐dominant AFLPs, informative within eight populations, failed to reveal any heterozygous individuals, indicating very high selfing rates (S̄H = 1). Estimates of nucleotide diversity within populations ranged from 0 to 0.00069 (0.00035 average), whereas the total nucleotide divergence among populations ranged from 0.00107 to 0.00382 (0.00247 average). Measures of population differentiation (GS) in terms of Shannon–Weaver diversity values and estimated nucleotide substitutions were 0.90 and 0.86, respectively. Although some of the sample populations contained a mixture of true breeding genotypes, most populations could be distinguished unambiguously. Moreover, geographical distance between the natural source populations was significantly correlated with genetic distance (r = 0.60) among the corresponding sample populations. Results indicate that inbreeding, combined with founder effects and/or selection, has contributed to the differentiation of N. pulchra populations. Foundation seed populations of the selected natural germplasm releases were genetically well defined and most similar to natural seed collected near the corresponding source populations. Thus, these commercial germplasm sources will be made practically available and useful for conservation plantings within the intended areas of utilization.
Spatial effects and rare outcrossing events in Medicago truncatula (Fabaceae)
Authors: Bonnin Isabelle , Ronfort Joelle , Wozniak Frederic , Olivieri Isabelle 
Published: March 2003

AbstractIn order to elucidate the mechanisms underlying the large amount of RAPD polymorphism found in 1990 in a population of the selfing annual Medicago truncatula GAERTN. (Fabaceae), we have analysed most of the individuals (n = 363) from the same population 6 years later using microsatellite loci. We confirm the result of the earlier study, namely that this population is very polymorphic and highly subdivided, with approximately 37% of the variance distributed among subpopulations, only 50 m apart one from another. We use standard F‐statistics analyses, linkage disequilibria, minimum spanning network, multilocus assignment tests and spatial autocorrelation analyses to test the hypotheses that spatial structure and outcrossing events are involved in maintaining the large amount of genetic diversity at the level of each subpopulation. Interestingly, fine‐scale spatial structure could be observed in only one subpopulation suggesting that other mechanisms are acting elsewhere. To the best of our knowledge, this is the first study of fine spatial genetic structure in a predominantly selfing species.
Microgeographic genetic structure in the yellow‐pine chipmunk (Tamias amoenus)
Authors: Schulte‐Hostedde Albrecht I. , Gibbs H. Lisle , Millar John S. 
Published: March 2003

AbstractWhile there is evidence for broad‐scale genetic structure in small mammals, few studies have used variable DNA‐based genetic markers to examine genetic differentiation at microgeographic (tens of kilometres) scales. Yellow‐pine chipmunks (Tamias amoenus) live in the heterogeneous landscape of the Rockies in southwest Alberta and are generally restricted to areas of low elevation. We used seven microsatellite loci to determine whether chipmunks show evidence of population genetic structure among three closely situated sites (< 15 km) in the Kananaskis Valley, Alberta. We found evidence for genetic structure in the form of significant differences in allele frequencies among populations and significantly nonzero values of FST for both overall and pairwise population comparisons. However, FIS values for each population were not significantly different from zero, suggesting little evidence for inbreeding within populations. Genetic differentiation probably occurs as a result of the strong effect of drift in very small (Ne≈ 25) populations of these animals even in the face of substantial immigration rates.
Host specificity and incidence ofTrypanosomain some African rainforest birds: a molecular approach
Authors: Sehgal Ravinder N. M. , Jones Hugh I. , Smith Thomas B. 
Published: March 2003

AbstractStudies of host–parasite interactions in birds have contributed greatly to our understanding of the evolution and ecology of disease. Here we employ molecular techniques to determine the incidence and study the host‐specificity of parasitic trypanosomes in the African avifauna. We developed a polymerase chain reaction (PCR)‐based diagnostic test that amplified the small subunit ribosomal RNA gene (SSU rRNA) ofTrypanosomafrom avian blood samples. This nested PCR assay complements and corroborates information obtained by the traditional method of blood smear analysis. The test was used to describe the incidence of trypanosomes in 479 host individuals representing 71 rainforest bird species from Cameroon, the Ivory Coast and Equatorial Guinea. Forty‐two (59%) of these potential host species harboured trypanosomes and 189 individuals (35%) were infected. To examine host and geographical specificity, we examined the morphology and sequenced a portion of the SSU rRNA gene from representative trypanosomes drawn from different hosts and collecting locations. In traditional blood smear analyses we identified two trypanosome morphospecies,T. aviumandT. everetti.Our molecular and morphological results were congruent in that these two morphospecies had highly divergent SSU rRNA sequences, but the molecular assay also identified cryptic variation inT. avium, in which we found seven closely allied haplotypes. The pattern of sequence diversity withinT. aviumprovides evidence for widespread trypanosome mixing across avian host taxa and across geographical locations. For example,T. aviumlineages with identical haplotypes infected birds from different families, whereas single host species were infected byT. aviumlineages with different haplotypes. Furthermore, some conspecific hosts from geographically distant sampling locations were infected with the same trypanosome lineage, but other individuals from those locations harboured different trypanosome lineages. This apparent lack of host or geographical specificity may have important consequences for the evolutionary and ecological interactions between parasitic trypanosomes and their avian hosts.
Phylogeographical structure, postglacial recolonization and barriers to gene flow in the distinctive Valais chromosome race of the common shrew (Sorex araneus)
Authors: Lugon‐Moulin N. , Hausser J. 
Published: March 2003

AbstractUsing one male‐inherited and eight biparentally inherited microsatellite markers, we investigate the population genetic structure of the Valais chromosome race of the common shrew (Sorex araneus) in the Central Alps of Europe. Unexpectedly, the Y‐chromosome microsatellite suggests nearly complete absence of male gene flow among populations from the St‐Bernard and Simplon regions (Switzerland). Autosomal markers also show significant genetic structuring among these two geographical areas. Isolation by distance is significant and possible barriers to gene flow exist in the study area. Two different approaches are used to better understand the geographical patterns and the causes of this structuring. Using a principal component analysis for which testing procedure exists, and partial Mantel tests, we show that the St‐Bernard pass does not represent a significant barrier to gene flow although it culminates at 2469 m, close to the highest altitudinal record for this species. Similar results are found for the Simplon pass, indicating that both passes represented potential postglacial recolonization routes into Switzerland from Italian refugia after the last Pleistocene glaciations. In contrast with the weak effect of these mountain passes, the Rhône valley lowlands significantly reduce gene flow in this species. Natural obstacles (the large Rhône river) and unsuitable habitats (dry slopes) are both present in the valley. Moreover, anthropogenic changes to landscape structures are likely to have strongly reduced available habitats for this shrew in the lowlands, thereby promoting genetic differentiation of populations found on opposite sides of the Rhône valley.
Mitochondrial DNA variation along an altitudinal gradient in the greater white‐toothed shrew, Crocidura russula
Authors: Ehinger M. , Fontanillas P. , Petit E. , Perrin N. 
Published: March 2003

AbstractThe distribution of mitochondrial control region‐sequence polymorphism was investigated in 15 populations of Crocidura russula along an altitudinal gradient in western Switzerland. High‐altitude populations are smaller, sparser and appear to undergo frequent bottlenecks. Accordingly, they showed a loss of rare haplotypes, but unexpectedly, were less differentiated than lowland populations. Furthermore, the major haplotypes segregated significantly with altitude. The results were inconsistent with a simple model of drift and dispersal. They suggested instead a role for historical patterns of colonization, or, alternatively, present‐day selective forces acting on one of the mitochondrial genes involved in metabolic pathways.
A Bayesian approach to inferring population structure from dominant markers
Authors: Holsinger Kent E. , Lewis Paul O. , Dey Dipak K. 
Published: March 2003

AbstractMolecular markers derived from polymerase chain reaction (PCR) amplification of genomic DNA are an important part of the toolkit of evolutionary geneticists. Random amplified polymorphic DNA markers (RAPDs), amplified fragment length polymorphisms (AFLPs) and intersimple sequence repeat (ISSR) polymorphisms allow analysis of species for which previous DNA sequence information is lacking, but dominance makes it impossible to apply standard techniques to calculateF‐statistics. We describe a Bayesian method that allows direct estimates ofFSTfrom dominant markers. In contrast to existing alternatives, we do not assume previous knowledge of the degree of within‐population inbreeding. In particular, we do not assume that genotypes within populations are in Hardy–Weinberg proportions. Our estimate ofFSTincorporates uncertainty about the magnitude of within‐population inbreeding. Simulations show that samples from even a relatively small number of loci and populations produce reliable estimates ofFST. Moreover, some information about the degree of within‐population inbreeding (FIS) is available from data sets with a large number of loci and populations. We illustrate the method with a reanalysis of RAPD data from 14 populations of a North American orchid,Platanthera leucophaea.
Extreme sex‐biased dispersal in the communally breeding, nonmigratory Bechstein's bat (Myotis bechsteinii)
Authors: Kerth G. , Mayer F. , Petit E. 
Published: March 2003

AbstractMaternity colonies of the communally breeding, nonmigratory Bechstein's bat consist of closely related females that live together with unrelated females, and average colony relatedness is low despite the absence of immigration. We compared the genetic structure of both nuclear and mitochondrial microsatellites in order to quantify sex‐specific dispersal rates. More specifically, we aimed at testing whether male dispersal is able to balance the genetic effect of strong (absolute) female philopatry. Absolute female philopatry, indicated by an extreme mitochondrial DNA population differentiation of 96%, was indeed opposed by strong (possibly complete) male dispersal. Based on our knowledge of the biology ofMyotis bechsteinii, we conclude that inbreeding avoidance is likely to be the crucial factor driving male dispersal in this species.
Clonal diversity and structure within a population of the pondweed Potamogeton pectinatus foraged by Bewick's swans
Authors: Hangelbroek H. H. , Ouborg N. J. , Santamaría L. , Schwenk K. 
Published: March 2003

AbstractClonal diversity within plant populations is affected by factors that influence genet (clone) survival and seed recruitment, such as resource availability, disturbance, seed dispersal mechanism, propagule predation and the age of the population. Here we studied a population of Potamogeton pectinatus, a pseudo‐annual aquatic macrophyte. Within populations reproduction appears to be mainly asexually through subterranean propagules (tubers), while recruitment via seeds is believed to be relatively unimportant. RAPD markers were used to analyse clonal diversity and genetic variation within the population. Ninety‐seven genets were identified among 128 samples taken from eight plots. The proportion of distinguishable genets (0.76) and Simpson's diversity index (0.99) exhibited high levels of clonal diversity compared to other clonal plants. According to an analysis of molecular variance (amova) most genetic variation occurred between individuals within plots (93–97%) rather than between plots (8–3%). These results imply that sexual reproduction plays an unexpectedly important role within the population. Nevertheless, autocorrelation statistics revealed a spatial genetic structure resulting from clonal growth. In contrast to genetic variation, clonal diversity was affected by several ecological factors. Water depth and silt content had direct negative effects on clonal diversity. Tuber predation by Bewick's swans had an unexpected indirect negative effect on clonal diversity through reducing the tuber‐bank biomass in spring, which on its turn was positively correlated to clonal diversity. The disturbance by swans, therefore, did not enhance seed recruitment and thus clonal diversity; on the contrary, heavily foraged areas are probably more prone to stochastic loss of genets leading to reduced clonal diversity.
Patterns of molecular genetic variation among African elephant populations
Authors: Comstock Kenine E. , Georgiadis Nicholas , Pecon‐Slattery Jill , Roca Alfred L. , Ostrander Elaine A. , O'Brien Stephen J. , Wasser Samuel K. 
Published: March 2003

AbstractThe highly threatened African elephants have recently been subdivided into two species, Loxodonta africana (savannah or bush elephant) and L. cyclotis (forest elephant) based on morphological and molecular studies. A molecular genetic assessment of 16 microsatellite loci across 20 populations (189 individuals) affirms species level genetic differentiation and provides robust genotypic assessment of species affiliation. Savannah elephant popula‐tions show modest levels of phylogeographic subdivision based on composite microsatellite genotype, an indication of recent population isolation and restricted gene flow between locales. The savannah elephants show significantly lower genetic diversity than forest elephants, probably reflecting a founder effect in the recent history of the savannah species.