bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of the population genetics and densities of five Pinanga palm species at Kuala Belalong, Brunei
Authors: Shapcott A.
Published: March 2003

This study investigated the effect of population density on the population genetic structure of five co‐occurring congeneric understorey palm species: Pinanga aristata, P. sp. aff. brevipes, P. dumetosa, P. tenella var. tenella and P. veitchii, all endemic to northern Borneo. The average population densities of the study species varied across a wide spectrum, ranging from 343 (plants per ha) in P. tenella to 10 (plants per ha) in P. veitchii. All species of Pinanga palms studied had quite high levels of genetic diversity (HE: 0.379, 0.256, 0.294, 0.133, 0.352). Genetic diversity (HE) was correlated with population density (D;rs = − 0.433, P < 0.01) and the average distance to the nearest conspecific neighbour (NN;rs = 0.576, P < 0.001) such that the most‐dense species had less genetic diversity and the less‐dense species had greater genetic diversity. Gene flow (Nm) among populations approximately followed a gradient of increasing species density and abundance, such that the most common species P. dumestosa had the greatest gene flow (Nm = 2.268) between its populations and the rarest, most sparsely distributed species P. sp. aff. brevipes had the lowest (Nm = 0.698). All species of Pinanga were effectively inbred (F: 0.760, 0.856, 0.640, 0.753, 0.674). The amount of homozygosity and inbreeding (HO, F) were not correlated (P > 0.05) with population density (D) or the distance between nearest neighbouring plants of the same species (NN).
Impact of gene flow from cultivated beet on genetic diversity of wild sea beet populations
Authors: Bartsch Detlef , Lehnen Marc , Clegg Janet , Pohl‐Orf Matthias , Schuphan Ingolf , Ellstrand Norman C.
Published: March 2003

Gene flow and introgression from cultivated plants may have important consequences for the conservation of wild plant populations. Cultivated beets (sugar beet, red beet and Swiss chard: Beta vulgaris ssp. vulgaris) are of particular concern because they are cross‐compatible with the wild taxon, sea beet (B.vs. ssp. maritima). Cultivated beet seed production areas are sometimes adjacent to sea beet populations; the numbers of flowering individuals in the former typically outnumber those in the populations of the latter. In such situations, gene flow from cultivated beets has the potential to alter the genetic composition of the nearby wild populations. In this study we measured isozyme allele frequencies of 11 polymorphic loci in 26 accessions of cultivated beet, in 20 sea beet accessions growing near a cultivated beet seed production region in northeastern Italy, and 19 wild beet accessions growing far from seed production areas. We found one allele that is specific to sugar beet, relative to other cultivated types, and a second that has a much higher frequency in Swiss chard and red beet than in sugar beet. Both alleles are typically rare in sea beet populations that are distant from seed production areas, but both are common in those that are near the Italian cultivated beet seed production region, supporting the contention that gene flow from the crop to the wild species can be substantial when both grow in proximity. Interestingly, the introgressed populations have higher genetic diversity than those that are isolated from the crop. The crop‐to‐wild gene flow rates are unknown, as are the fitness consequences of such alleles in the wild. Thus, we are unable to assess the long‐term impact of such introgression. However, it is clear that gene flow from a crop to a wild taxon does not necessarily result in a decrease in the genetic diversity of the native plant.
Marine population structure in an anadromous fish: life‐history influences patterns of mitochondrial DNA variation in the eulachon, Thaleichthys pacificus
Authors: McLean Jennifer E. , Hay D. E. , Taylor Eric B.
Published: March 2003

Due to the apparent decline in size of a number of populations, eulachon, Thaleichthys pacificus, have recently become the focus of a conservation movement in the northeast Pacific. Little is known of the marine life‐history phase of this anadromous fish, and although it has been suggested that eulachon spawning in different rivers may form distinct populations, nothing is known of their population structure. Molecular genetic data were used to investigate population structure and possible management schemes. Mitochondrial DNA genotypes, determined through restriction fragment length polymorphisms (RFLP) analysis, were resolved in fish from several rivers throughout the geographical range of eulachon. Our data support the idea that extant eulachon populations result from postglacial dispersal from a single Wisconsinan glacial refuge. Further, while three of the 37 haplotypes recovered account for approximately 79% of the samples, many private haplotypes were observed, suggesting possible regional population structure. While a great deal of genetic variation was observed (37 haplotypes in 315 samples), an amova showed that > 97% of the total variation was detected within populations. As yet, it is unclear whether genetically distinct populations of eulachon exist, or if these fish may be treated as one or a few large populations. Results were tested against predictions made from hypotheses concerning the origin and persistence of subdivided populations in marine species, and seem to be more consistent with the Member–Vagrant hypothesis than isolation by distance. Eulachon present an interesting situation that illustrates the difficulties involved in defining management units in organisms with high levels of gene flow.
A microsatellite‐based estimation of clonal diversity and population subdivision in Zostera marina, a marine flowering plant
Authors: Reusch T. B. H. , Stam W. T. , Olsen J. L.
Published: March 2003

We examined the genetic population structure in eelgrass (Zostera marina L.), the dominant seagrass species of the northern hemisphere, over spatial scales from 12 km to 10 000 km using the polymorphism of DNA microsatellites. Twelve populations were genotyped for six loci representing a total of 67 alleles. Populations sampled included the North Sea (four), the Baltic Sea (three), the western Atlantic (two), the eastern Atlantic (one), the Mediterranean Sea (one) and the eastern Pacific (one). Microsatellites revealed substantial genetic variation in a plant group with low allozyme diversity. Average expected heterozygosities per population (monoclonal populations excluded) ranged from 0.32 to 0.61 (mean = 0.48) and allele numbers varied between 3.3 and 6.7 (mean = 4.7). Using the expected frequency of multilocus genotypes within populations, we distinguished ramets from genetic individuals (i.e. equivalent to clones). Differences in clonal diversity among populations varied widely and ranged from maximal diversity (i.e. all ramets with different genotype) to near or total monoclonality (two populations). All multiple sampled ramets were excluded from further analysis of genetic differentiation within and between populations. All but one population were in Hardy–Weinberg equilibrium, indicating that Zostera marina is predominantly outcrossing. From a regression of the pairwise population differentiation with distance, we obtained an effective population size Ne of 2440–5000. The overall genetic differentiation among eelgrass populations, assessed as ρ (a standardized estimate of Slatkin’s RST) was 0.384 (95% CI 0.34–0.44, P < 0.001). Genetic differentiation was weak among three North Sea populations situated 12–42 km distant from one another, suggesting that tidal currents result in an efficient exchange of propagules. In the Baltic and in Nova Scotia, a small but statistically significant fraction of the genetic variance was distributed between populations (ρ = 0.029−0.053) at scales of 15–35 km. Pairwise genetic differentiation between European populations were correlated with distance between populations up to a distance of 4500 km (linear differentiation‐by‐distance model, R2 = 0.67). In contrast, both Nova Scotian populations were genetically much closer to North Sea and Baltic populations than expected from their geographical distance (pairwise ρ = 0.03−0.08, P < 0.01). A biogeographical cluster of Canadian with Baltic/North Sea populations was also supported using a neighbour‐joining tree based on Cavalli–Sforza’s chord distance. Relatedness between populations may be very different from predictions based on geographical vicinity.
Molecular systematics, biogeography and population structure of Neotropical freshwater needlefishes of the genus Potamorrhaphis
Authors: Lovejoy N. R. , De Araújo M. L. G.
Published: March 2003

Phylogenetic relationships of populations and species within Potamorrhaphis, a genus of freshwater South American needlefishes, were assessed using mitochondrial cytochrome b sequences. Samples were obtained from eight widely distributed localities in the Amazon and Orinoco rivers, and represented all three currently recognized species of Potamorrhaphis. The phylogeny of haplotypes corresponded imperfectly to current morphological species identities: haplotypes from P. guianensis, the most widespread species, did not make up a monophyletic clade. Geography played a strong role in structuring genetic variation: no haplotypes were shared between any localities, indicating restricted gene flow. Possible causes of this pattern include limited dispersal and the effects of current and past geographical barriers. The haplotype phylogeny also showed a complex relationship between fishes from different river basins. Based on the geographical distribution of clades, we hypothesize a connection between the middle Orinoco and Amazon via rivers of the Guianas. More ancient divergence events may have resulted from Miocene alterations of river drainage patterns. We also present limited data for two other Neotropical freshwater needlefish genera: Belonion and Pseudotylosurus. Pseudotylosurus showed evidence of substantial gene flow between distant localities, indicating ecological differences from Potamorrhaphis.
Sex ratio and fledging success of supplementary‐fed Tengmalm’s owl broods
Authors: Hörnfeldt B. , Hipkiss T. , Fridolfsson A.‐K. , Eklund U. , Ellegren H.
Published: March 2003

A nest box population of Tengmalm’s owls (Aegolius funereus) in northern Sweden was studied to investigate the effects of extra food on the sex ratio between hatching and fledging in this sexually size‐dimorphic species. The brood size and brood sex ratio of supplementary‐fed and control broods were compared. Newly hatched nestlings were blood sampled and sexed by polymerase chain reaction (PCR) amplification of the sex‐linked CHD1Z and CHD1W genes. The brood sex ratio at hatching was strongly male biased (65%); this was also the case in broods where all eggs hatched (72%). There was no relationship between hatch order and sex ratio, and hatching sex ratio did not vary significantly with laying date. Brood size decreased between hatching and fledging, but did not differ between fed and control broods at either stage. Brood sex ratio did not differ between hatching and fledging, and fledging sex ratio did not differ between fed and control broods. It was concluded that, at least during the year in which the study was carried out, feeding had no effect on brood reduction, and that male and female nestlings did not show any differential mortality. The mechanisms behind the male‐biased sex ratio at hatching, and any possible adaptive reasons for it, are not known.
Sex, parthenogenesis and genetic structure of rotifers: microsatellite analysis of contemporary and resting egg bank populations
Authors: Gómez A. , Carvalho G. R.
Published: March 2003

Cyclically parthenogenetic rotifers are a valuable model for investigating the relationship between reproductive mode and population structure, although advances in this field have been hindered by low allozyme variability in these organisms. A high genotypic diversity is predicted after population establishment, which would be eroded by clonal selection during the parthenogenetic phase. The resting egg bank, produced sexually, is presumed to store high levels of genetic diversity, with subsequent effects on planktonic population structure. Here, we provide the first application of microsatellite markers to a rotifer planktonic population and its associated resting egg bank. Seven polymorphic microsatellite loci were screened in populations of the rotifer Brachionus plicatilis in a temporary pond to analyse: (i) the genetic structure of the resting egg bank; (ii) the changes in the genetic structure of rotifer populations during the parthenogenetic phase; and (iii) the population structure after its initiation from resting eggs. Microsatellites proved to be a useful tool for clone identification, revealing a surprisingly high clonal diversity in rotifer populations. The last sample in the parthenogenetic phase showed evidence of clonal selection, as indicated by a low observed clonal diversity and the appearance of linkage disequilibria. The resting egg bank, analysed comprehensively for the first time in any zooplankter, is in Hardy–Weinberg and linkage equilibrium, and contains a high genotypic diversity. Unexpectedly, the resting egg bank differed from the planktonic population in its allelic composition, suggesting that resting egg hatching is biased.
Origin and evolution of invasive naturalized material ofRhododendron ponticumL. in the British Isles
Authors: Milne Richard I. , Abbott Richard J.
Published: March 2003

Information concerning the area of origin, genetic diversity and possible acquisition of germplasm through hybridization is fundamental to understanding the evolution, ecology and possible control measures for an introduced invasive plant species.Rhododendron ponticumis extensively naturalized in the British Isles, but it is not known whether native material in Turkey, Spain or Portugal gave rise to the naturalized material, or to what extent introgression has affected this material. Chloroplast (cp) and nuclear ribosomal DNA (rDNA) restriction fragment length polymorphisms (RFLPs) were sought which could distinguish between native material ofR. ponticum, and between 15 otherRhododendronspecies includingR. ponticum's closest relatives. Thereafter, a total of 260 naturalized accessions ofR. ponticumfrom throughout the British Isles was examined with respect to informative polymorphisms. It was found that 89% of these accessions possessed a cpDNA haplotype that occurred in native material ofR. ponticumderived almost entirely from Spain, while 10% of accessions had a haplotype unique to Portuguese material. These results therefore indicated an Iberian origin for British material. rDNA or cpDNA evidence of introgression fromR. catawbiensewas found in 27 British accessions ofR. ponticum, and such accessions were significantly more abundant in Britain's coldest region, eastern Scotland, than elsewhere. This could indicate that introgression fromR. catawbienseconfers improved cold tolerance. Introgression fromR. maximumand an unidentified species was also detected.
Delineation of genetic zones in the European Norway spruce natural range: preliminary evidence
Authors: Bucci Gabriele , Vendramin Giovanni Giuseppe
Published: March 2003

We applied geostatistics to previously reported chloroplast simple sequence repeats (cpSSR) haplotype frequency data from 95 European Norway spruce populations to provide preliminary evidence about the following issues: (i) delineation of genetically homogeneous regions (‘genetic zones’); (ii) prediction of their haplotype frequencies and definition of related criteria to be applied for provenance identification and certification of seedlots; (iii) identification of putative allochthonous stands; and (iv) construction of a continental‐scale ‘availability map’ of the intraspecific biodiversity for Norway spruce. Direct evidence of large‐scale geographical structure over the European natural range was obtained, detecting both geographical clines and stationary patterns. The increase of the mean genetic divergence by geographical distance (up to approximately 1800 km apart) provided a strong hint that geographical distance is a major factor of differentiation in Norway spruce. Haplotype frequency surfaces were obtained by applying ordinary kriging to sampling frequency data. Cluster analysis carried out on haplotype frequency surfaces revealed a fair discrimination among 16 genetic zones, with an accuracy of 0.916. Dendrogram analysis carried out on the predicted mean haplotype frequency confirmed a fairly good separability of the genetic zones detected. Reclassification of populations by discriminant analysis confirmed the robustness of the genetic subdivision obtained. Combining the information from discriminant analysis and cross‐validation of sampling points, three populations likely to be of nonlocal origin were identified. The application of geostatistical analysis to genetic marker data is discussed in relation to breeding activities and to the formulation of appropriate conservation strategies.
Genetic evidence for host specificity in the hemi‐parasitic Viscum album L. (Viscaceae)
Authors: Zuber D. , Widmer A.
Published: March 2003

Nuclear ribosomal DNA (nrDNA) ITS sequences and partial sequences of three non‐coding chloroplast DNA (cpDNA) introns and spacers were used to assess genetic variation within and among three presumed host races of the hemi‐parasite Viscum album L. Currently, identification of host races occurs via the host trees, and morphological differences are minute at best. cpDNA and nrDNA ITS sequences revealed little sequence variation, but the variation found consistently supported the distinction of three host races. cpDNA and ITS sequences were not incongruent, as assessed by the incongruence length difference test. A combined analysis supported the sister group relationship between mistletoes from deciduous trees and fir.
Population subdivision in Europe’s great bustard inferred from mitochondrial and nuclear DNA sequence variation
Authors: Pitra C. , Lieckfeldt D. , Alonso J. C.
Published: March 2003

A continent‐wide survey of sequence variation in mitochondrial (mt) and nuclear (n) DNA of the endangered great bustard (Otis tarda) was conducted to assess the extent of phylogeographic structure in a morphologically monotypic bird. DNA sequence variation in a combined 809 bp segment of the mtDNA genome from 66 individuals from the last six breeding regions showed relatively low levels of intraspecific sequence diversity (π = 0.32%) but significant differences in the regional distribution of 11 haplotypes (ΦST = 0.49). Despite their exceptional potential for dispersal, a complete and long‐term historical separation between the populations from the Iberian Peninsula (Spain) and mainland Europe (Hungary, Slovakia, Germany, and Russia) was demonstrated. Divergence between populations based on a 3‐bp insertion–deletion polymorphism within the intron region of the nuclear CHD‐Z gene was geographically concordant with the primary subdivision identified within the mtDNA sequences. Inferred aspects of phylogeography were used to formulate conservation recommendations for this endangered species.
Absence of a genetic bottleneck in a wild rabbit (Oryctolagus cuniculus) population exposed to a severe viral epizootic
Authors: Queney G. , Ferrand N. , Marchandeau S. , Azevedo M. , Mougel F. , Branco M. , Monnerot M.
Published: March 2003

Infectious diseases and their demographic consequences are thought to influence the genetic diversity of populations. In Europe, during the last 50 years, the European rabbit (Oryctolagus cuniculus) has suffered two important viral epizootics: myxomatosis and rabbit viral haemorraghic disease (RVHD). Although mortality rates were very high, the impact of these diseases on genetic diversity has never been assessed directly. The subject of this paper is a wild rabbit population in France, which has been studied since the beginning of the 1980s. The first outbreak of RVHD occurred in 1995 and provoked a demographic crash. The population, sampled for the first time in 1982 and 1994, was sampled again at the end of 1996 to examine the impact of the epizootic on genetic diversity. In spite of the observed high mortality rate (≈ 90%), analysis of 14 polymorphic loci (allozymes and microsatellites) showed no loss in genetic diversity after the epizootic. Determination of temporal changes in allele frequencies indicated that the population evolved under genetic drift. The temporal method of Waples demonstrated a significant decrease in the effective population size (Ne) correlated with the demographic crash due to the epizootic. However, the population had only been studied for two generations after the epizootic and the remnant population size probably stayed high enough (≈ 50 individuals) to keep its genetic diversity at the precrash level. These results suggest that, contrary to what is usually thought and in spite of the subsequent high mortality rates, past epizootics (especially myxomatosis) may have had little effect on the genetic diversity of wild rabbit populations in Europe.
Glacial vicariance and historical biogeography of rock ptarmigan (Lagopus mutus) in the Bering region
Authors: Holder K. , Montgomerie R. , Friesen V. L.
Published: March 2003

In this paper, we address alternative hypotheses for the evolution of subspecies of rock ptarmigan (Lagopus mutus) endemic to the Aleutian Archipelago. To do this we examined patterns of genetic differentiation among populations of rock ptarmigan in the Aleutian Islands and parts of both Alaska and Siberia. Variation in mitochondrial control region sequences of 105 rock ptarmigan from 10 subspecies within the Bering region revealed three major phylogenetic lineages, two of which are endemic to the Aleutian Islands. Accordingly, haplotype and nucleotide diversities of rock ptarmigan within the archipelago are much higher than within mainland Alaska or Siberia. For Aleutian rock ptarmigan, analyses of molecular variance indicated significant genetic structuring and low estimates of gene flow among populations, despite small interisland distances within the archipelago. However, isolation by distance did not describe the pattern of gene flow or differentiation at this scale. Our estimates of divergence times of lineages suggest that Aleutian rock ptarmigan became isolated prior to the most recent Pleistocene glaciation event (late Wisconsin Stade) and that current patterns of genetic variation reflect the postglacial redistribution of divergent lineages and subsequent limited gene flow. In addition, genetic divergence among lineages was concordant with the distribution of plumage types among subspecies. The patterns of genetic variation described here for rock ptarmigan provide evidence for the role of glacial vicariance in contributing to genetic diversity within this and other Bering region species.
Genetic differentiation of Euterpe edulis Mart. populations estimated by AFLP analysis
Authors: Cardoso S. R. S. , Eloy N. B. , Provan J. , Cardoso M. A. , Ferreira P. C. G.
Published: March 2003

Heart‐of‐palm (Euterpe edulis Mart.) is a wild palm with a wide distribution throughout the Atlantic Rainforest. Populations of E. edulis represent important renewable natural resources but are currently under threat from predatory exploitation. Furthermore, because the species is indigenous to the Atlantic Rainforest, which is located in the most economically developed and populated region of Brazil, social and economic pressures have devastated heart‐of‐palm forests. In order to estimate the partitioning of genetic variation of endangered E. edulis populations, 429 AFLP markers were used to analyse 150 plants representing 11 populations of the species distribution range. Analysis of the genetic structure of populations carried out using analysis of molecular variance (amova) revealed moderate genetic variation within populations (57.4%). Genetic differentiation between populations (FST = 0.426) was positively correlated with geographical distance. These results could be explained by the historical fragmentation of the Atlantic coastal region, together with the life cycle and mating system. The data obtained in this work should have important implications for conservation and future breeding programmes of E. edulis.
Evolution of balanced genetic polymorphism
Authors: Richman Adam
Published: March 2003

Extreme genetic polymorphism maintained by balancing selection (so called because many alleles are maintained in a balance by a mechanism of rare allele advantage) is intimately associated with the important task of self/non‐self‐discrimination. Widely disparate self‐recognition systems of plants, animals and fungi share several general features, including the maintenance of large numbers of alleles at relatively even frequency, and persistence of this variation over very long time periods. Because the evolutionary dynamics of balanced polymorphism are very different from those of neutral genetic variation, data on balanced polymorphism have been used as a novel source for inference of the history of populations. This review highlights the unique evolutionary properties of balanced genetic polymorphism, and the use of theoretical understanding in analysis and application of empirical data for inference of population history. However, a second goal of this review is to point out where current theory is incomplete. Recent observations suggest that entirely novel selective forces may act in concert with balancing selection, and these novel forces may be extremely potent in shaping genetic variation at self‐recognition loci.
Limited differentiation in microsatellite DNA variation among northern populations of the yellow warbler: evidence for male‐biased gene flow?
Authors: Gibbs H. Lisle , Dawson Robert J. G. , Hobson Keith A.
Published: March 2003

Comparisons of the patterns of differentiation among genetic markers with different modes of inheritance can provide insights into patterns of sex‐biased dispersal and gene flow. Here, we compare the patterns of differentiation in six microsatellite loci among eight northern breeding populations of the yellow warbler (Dendroica petechia) with results obtained with mitochondrial DNA. Significant but low levels of differentiation (overall FST = 0.014; overall RST = 0.015) were present across all populations. The level of differentiation is substantially less than that observed in the same samples based on mitochondrial DNA control region variation. The presence of low population imbalance index values and significant isolation‐by‐distance relationships for both FST and RST suggests that these populations are at evolutionary equilibrium and that the high degree of similarity between populations may be due to high levels of male‐biased gene flow. This suggests that there may be significant but previously unappreciated differences in the long‐distance and/or episodic dispersal behaviour of males and females in these birds.
Anarchy in the UK: Detailed genetic analysis of worker reproduction in a naturally occurring British anarchistic honeybee,Apis mellifera, colony using DNA microsatellites
Authors: Châline N. , Ratnieks F. L. W. , Burke T.
Published: March 2003

Anarchistic behaviour is a very rare phenotype of honeybee colonies. In an anarchistic colony, many workers’ sons are reared in the presence of the queen. Anarchy has previously been described in only two Australian colonies. Here we report on a first detailed genetic analysis of a British anarchistic colony. Male pupae were present in great abundance above the queen excluder, which was clearly indicative of extensive worker reproduction and is the hallmark of anarchy. Seventeen microsatellite loci were used to analyse these male pupae, allowing us to address whether all the males were indeed workers’ sons, and how many worker patrilines and individual workers produced them. In the sample, 95 of 96 of the males were definitely workers’ sons. Given that ≈ 1% of workers’ sons were genetically indistinguishable from queen's sons, this suggests that workers do not move any queen‐laid eggs between the part of the colony where the queen is present to the area above the queen excluder which the queen cannot enter. The colony had 16 patrilines, with an effective number of patrilines of 9.85. The 75 males that could be assigned with certainty to a patriline came from 7 patrilines, with an effective number of 4.21. They were the offspring of at least 19 workers. This is in contrast to the two previously studied Australian naturally occurring anarchist colonies, in which most of the workers’ sons were offspring of one patriline. The high number of patrilines producing males leads to a low mean relatedness between laying workers and males of the colony. We discuss the importance of studying such colonies in the understanding of worker policing and its evolution.
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

Intraspecific 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

We 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

There 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

The 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

The 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

A 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

In 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

While 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

Studies 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

Using 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

The 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

Molecular 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

Maternity 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.