bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal change in the opportunity for sexual selection
Authors: REICHARD M. , SMITH C. , BRYJA J. 
Published: September 2010

AbstractEnvironmental and population parameters that influence the strength of sexual selection may vary considerably over the course of the reproductive season. However, the potential for sexual selection frequently fails to translate into variation in reproductive success among individuals. We investigated seasonal changes in variation in reproductive success, measured as the opportunity for sexual selection, using parentage analysis in 20 experimental populations of the European bitterling (Rhodeus amarus, Cyprinidae), a small freshwater fish with a promiscuous, resource‐based mating system. We showed that although the largest males sired most offspring over the entire reproductive season, variation in reproductive success and hence the opportunity for sexual selection was low at the start of the season but increased significantly at its end. This seasonal difference probably arose from the superior competitive endurance of large males and from a higher temporal clustering of reproductively active females at the start of the breeding season than later in the season. The spatial distribution of oviposition sites had a negligible effect on the variation in reproductive success. We discuss the potential implications of our results for the importance and strength of sexual selection in natural populations.
Insight into the routes of Wolbachia invasion: high levels of horizontal transfer in the spider genus Agelenopsis revealed by Wolbachia strain and mitochondrial DNA diversity
Authors: BALDO LAURA , AYOUB NADIA A. , HAYASHI CHERYL Y. , RUSSELL JACOB A. , STAHLHUT JULIE K. , WERREN JOHN H. 
Published: September 2010

AbstractThe pandemic distribution of Wolbachia (alpha‐proteobacteria) across arthropods is largely due to the ability of these maternally inherited endosymbionts to successfully shift hosts across species boundaries. Yet it remains unclear whether Wolbachia has preferential routes of transfer among species. Here, we examined populations of eight species of the North American funnel‐web spider genus Agelenopsis to evaluate whether Wolbachia show evidence for host specificity and the relative contribution of horizontal vs. vertical transmission of strains within and among related host species. Wolbachia strains were characterized by multilocus sequence typing (MLST) and Wolbachia surface protein (WSP) sequences, and analysed in relation to host phylogeny, mitochondrial diversity and geographical range. Results indicate that at least three sets of divergent Wolbachia strains invaded the genus Agelenopsis. After each invasion, the Wolbachia strains preferentially shuffled across species of this host genus by horizontal transfer rather than cospeciation. Decoupling of Wolbachia and host mitochondrial haplotype (mitotypes) evolutionary histories within single species reveals an extensive contribution of horizontal transfer also in the rapid dispersal of Wolbachia among conspecific host populations. These findings provide some of the strongest evidence to support the association of related Wolbachia strains with related hosts by means of both vertical and horizontal strain transmission. Similar analyses across a broader range of invertebrate taxa are needed, using sensitive methods for strain typing such as MLST, to determine if this pattern of Wolbachia dispersal is peculiar to Agelenopsis (or spiders), or is in fact a general pattern in arthropods.
Insight into the genetic bases of climatic adaptation in experimentally evolving wheat populations
Authors: RHONÉ BÉNÉDICTE , REMOUÉ CARINE , GALIC NATHALIE , GOLDRINGER ISABELLE , BONNIN ISABELLE 
Published: September 2010

AbstractExperimental populations evolving under natural selection represent an interesting tool to study genetic bases of adaptation. Evolution of genes possibly involved in adaptive response can be followed together with the corresponding phenotypic traits. Using experimental populations of hexaploid wheat, we studied the evolution of flowering time, a major adaptive trait that synchronizes the initiation of reproduction and the occurrence of favourable environmental conditions. During 12 generations, three populations were grown in contrasted environments (Vervins North France, Le Moulon near Paris, Toulouse South France) under the influence of natural selection, drift, mutation and recombination. Evolution of diversity at the major gene VRN‐1 involved in wheat vernalization response has been analysed jointly with earliness estimated in controlled conditions. Whatever the population, rapid phenotypic changes as well as parallel genotypic variations were observed in the first seven generations, probably as the result of selection acting on this major gene which explains 80% of the trait variation overall. Different allelic combinations at physically unlinked copies of VRN‐1 located on distinct genomes (A, B and D) were selected between populations. As theoretically expected, due to population differentiation, a high level of genetic diversity was maintained overall in generation 12. Surprisingly, in two populations out of three, the emergence of new alleles by mutation or migration, coupled with temporal variable selection or frequency‐dependent selection, allowed to maintain within‐population diversity despite local genetic drift and natural selection. This result may plead for an evolutionary approach of wheat genetic resource conservation.
Soft selective sweep near a gene that increases plant height in wheat
Authors: RAQUIN A.‐L. , BRABANT P. , RHONÉ B. , BALFOURIER F. , LEROY P. , GOLDRINGER I. 
Published: September 2010

AbstractStrong selection within a given population locally reduces genetic variability not only in the selected gene itself but also in neighbouring loci. This so‐called hitch‐hiking effect is related to the initial linkage disequilibrium between markers and the selected gene, and depends mainly on the number of copies of the beneficial allele at the start of the selection phase. Contrary to the classical case, in which selection acts on a single, newly arisen beneficial mutation, we considered selection from standing variation (soft selective sweeps) on a gene (Rht‐B1) with a major effect on plant height, a selected trait in an experimental wheat population grown for 17 generations, and we documented the evolution of gene diversity and linkage disequilibrium near this gene. As expected,Rht‐B1was found to be under strong selection (s = 0.15) and its variation in frequency accounted for 15% of the total trait evolution. This led to a smaller genetic effective population size atRht‐B1(Neg = 18) compared to the whole genome estimation (Neg = 167). When compared with expectations under genetic drift only, no significant decrease in gene diversity was found at the closest loci. We computed expected di‐locus frequencies for any linked marker–Rht‐B1pair due to hitch‐hiking effects. We found that hitch‐hiking was expected to affect the two most closely linked loci, but expected reduction in gene diversity was not greater than that due to genetic drift, which was consistent with the observations. Such limited effect was attributed to the low level of linkage disequilibrium (0.16) estimated after parental intercrosses, together with a relatively high initial frequency of the gene. This situation is favourable to candidate gene approaches where small linkage disequilibrium around selected genes is expected.
Hotspots of diversity in a clonal world — the Mediterranean moss Pleurochaete squarrosa in Central Europe
Authors: GRUNDMANN MICHAEL , ANSELL STEPHEN W. , RUSSELL STEPHEN J. , KOCH MARCUS A. , VOGEL JOHANNES C. 
Published: September 2010

AbstractDiversity patterns of the dioecious haploid Mediterranean moss Pleurochaete squarrosa were analysed from Central and Northwest Europe using nuclear and chloroplast DNA sequencing and enzyme electrophoresis. Across 69 populations, 38 distinct haploid multilocus genotypes (MLGs) were detected, but nearly all populations were clonal. Only five MLGs occurred in more than two regions, and two diversity hotspots were detected. The Kaiserstuhl mountains in Southwest Germany harboured 34 MLGs, 25 being endemic within Central Europe. Levels of linkage disequilibrium and population structure in Kaiserstuhl populations were similar to levels and structure in sexually reproducing populations in the Mediterranean Basin. In the Moselle‐Nahe area, some 250 km north, a comparably high allelic diversity, but no evidence of recombination, was detected. Genetic diversity measures were significantly lower than estimates obtained in the Mediterranean Basin and a GST of 0.89 signified extreme population differentiation. Mantel tests identified a positive correlation on genetic and geographical distance for distances up to 50 km. Seven nrITS and three cpDNA haplotypes were detected, their geographical structure mirroring enzyme data set results. Comparative analysis with Mediterranean data demonstrated multiple recolonization of Central Europe from both the Iberian Peninsula and the Balkans. A suture zone of genotypes was detected along the border of Belgium/France and Germany. Despite P. squarrosa having haploid spore and/or vegetative propagules dispersal, we found patterns of postglacial recolonization of Central Europe comparable with those reported in flowering plants and animals. This study demonstrates the importance of comparative research on population genetics and phylogeography of a diverse range of organisms.
Dispersal, recruitment and migratory behaviour in a hawksbill sea turtle aggregation
Authors: VELEZ‐ZUAZO XIMENA , RAMOS WILLY D. , VAN DAM ROBERT P. , DIEZ CARLOS E. , ABREU‐GROBOIS ALBERTO , MCMILLAN W. OWEN 
Published: September 2010

AbstractWe investigated the dispersal, recruitment and migratory behaviour of the hawksbill sea turtle (Eretmochelys imbricata), among different life‐history stages and demographic segments of the large hawksbill turtle aggregation at Mona Island, Puerto Rico. There were significant differences in both mitochondrial DNA (mtDNA) haplotype diversity and haplotype frequencies among the adult males, females and juveniles examined, but little evidence for temporal heterogeneity within these same groups sampled across years. Consistent with previous studies and the hypothesis of strong natal homing, there were striking mtDNA haplotype differences between nesting females on Mona Island and nesting females in other major Caribbean rookeries. Breeding males also showed strong, albeit weaker, genetic evidence of natal homing. Overall, Bayesian mixed‐stock analysis suggests that Mona Island was the natal rookery for 79% (65–94%) of males in the aggregation. In contrast, the Mona Island rookery accounted for only a small subset of the new juvenile recruits to the foraging grounds or in the population of older juvenile hawksbills turtles on Mona. Instead, both new recruits and the older juvenile hawksbill turtles on Mona more likely recruited from other Caribbean rookeries, suggesting that a mechanism besides natal homing must be influencing recruitment to feeding habitats. The difference in the apparent degree of natal homing behaviour among the different life‐history stages of hawksbill turtles at Mona Island underscores the complexity of the species’ life‐history dynamics and highlights the need for both local and regional conservation efforts.
Adapting to winter in wheat: a long‐term study follows parallel phenotypic and genetic changes in three experimental wheat populations
Authors: STRASBURG JARED L. , GROSS BRIANA L. 
Published: September 2010

AbstractDrawing a direct connection between adaptive evolution at the phenotypic level and underlying genetic factors has long been a major goal of evolutionary biologists, but the genetic characterization of adaptive traits in natural populations is notoriously difficult. The study of evolution in experimental populations offers some help — initial conditions are known and changes can be tracked for extended periods under conditions more controlled than wild populations and more realistic than laboratory or greenhouse experiments. In this issue of Molecular Ecology, researchers studying experimental wheat populations over a 12‐year period have demonstrated evolution in a major adaptive trait, flowering time, and parallel changes in underlying genetic variation (Rhonéet al. 2008). Their work suggests that cis‐regulatory mutations at a single gene may explain most of the flowering time variation in these populations.
Tracking elusive timber rattlers with molecular genetics
Authors: SHINE RICHARD 
Published: September 2010

AbstractMost biologists would agree that understanding the factors that influence gene flow among populations is important, because population connectivity is critical to effective conservation and management as well as to issues such as disease transmission and the degree of local adaptation. Nonetheless, our understanding of the mechanistic determinants of gene flow remains abysmally limited for many types of organisms. Predictably, some of the biggest gaps involve animals that are rare, secretive, and difficult to collect or handle — and thus, remain relatively unstudied for other traits as well. Large venomous snakes have long provided a classic example of such an under‐studied group, but the situation has changed dramatically over recent years. The study by Clark et al. in this issue builds upon our increasingly sophisticated understanding of snake behaviour, to interpret patterns of gene flow in the light of our emerging knowledge of snake behavioural ecology.
Morphology, sedimentology and palaeohydraulic significance of large gravel dunes, Altai Mountains, Siberia
Authors: CARLING P. A. 
Published: September 2010

ABSTRACTCoarse‐gravel bedforms which resulted from Pleistocene glacial outburst floods are identified as subaqueous dunes. Comparison of the morphology of these ‘fossil’ structures with modern dunes shows that the form of two‐dimensional (2‐D) transverse dunes and 3‐D cuspate and lunate dunes developed in coarse gravels is comparable with sand‐dune morphology within lesser‐scale geophysical flows. The similarity of the steepest gravel dunes with equilibrium dunes in sand indicates that grain size is not a major factor in constraining primary duneform.Internal structure indicates that flow over 2‐D dunes was relatively uniform but over 3‐D bedforms flow was locally variable. Flow separation and complex streaming of flow occurred over the steepest 3‐D dunes. Cross‐beds are thin and few approach the angle of repose; consequently most dunes did not migrate primarily by avalanching but by stoss‐entrained gravel transported over the crests rolling‐down and depositing on the lee slopes.Lee‐side sediments are often finer than the stoss‐slope sediments, which indicates the lee formed when flood power was waning. Some dunes were slightly planed‐down during falling stage because lee‐side cross‐beds tend to be steeper than the angle of the preserved lee slope. However, silt‐rich caps indicate that any height reduction was contemporary with the final deposition of foresets. Post‐flood modification has been negligible although the modern topography is subdued by loess deposits within the dune troughs.
Microspar development during early marine burial diagenesis: a comparison of Pliocene carbonates from the Bahamas with Silurian limestones from Gotland (Sweden)
Authors: MUNNECKE AXEL , WESTPHAL HILDEGARD , REIJMER JOHN J. G. , SAMTLEBEN CHRISTIAN 
Published: September 2010

ABSTRACTComparison of ultrastructures in Pliocene periplatform carbonates from the Bahamas with Silurian limestones from Gotland (Sweden) reveals that despite the differences in primary sediment composition and age, they reflect a similar mechanism of lithification. In both sequences calcite microspar was formed as a primary cement at an early stage of marine burial diagenesis. Neither significant compression nor meteoric influence are necessary for the formation of calcite microspar. A model is proposed for the process of microsparitic cementation of fine‐grained aragonite needle muds comprising four stages: (1) unconsolidated, aragonite‐dominated carbonate mud; (2) precipitation of microspar that engulfs aragonite needles; (3) dissolution of aragonite, resulting in pitted surfaces of the microspar crystals; and (4) slight recrystallization. Our results contradict the widespread opinion that microspar necessarily is a product of secondary recrystallization of a previously lithified micrite.
Grain size distribution expressed as tanh‐functions
Authors: P°SSE TORE 
Published: September 2010

ABSTRACTThe grain size distribution within a unimodal sediment can be described as a lognormal distribution when the distribution is formed by only one process. However, most sediments are formed by more than one process giving polymodal sediments. Polymodal sediments have to be described as the sum of several normal distributions, one for each process involved within the formation.Grain size distributions are usually interpreted with the help of graphical methods. Interpretations of polymodal sediments require mathematical methods. In mathematical terms a unimodal sediment can be described as a tangential hyperbolic function (tanh) and a polymodal sediment can generally be described by the sum of two or three tanh‐functions. The tanh‐method is a tool for identifying and estimating the number of modes within a grain size distribution and helps interpret the processes involved within the formation of a deposit. The mathematical method can also be used to computerize sediment data, allowing storage with just a few numbers. Different samples can easily be compared and classified. Also, this method could be a valuable tool for calculations of various sediment parameters both in geotechnology and hydrogeology.
On the transition between 2D and 3D dunes
Authors: VENDITTI JEREMY G. , CHURCH MICHAEL , BENNETT SEAN J. 
Published: September 2010

AbstractSediment transport in sand‐bedded alluvial channels is strongly conditioned by bedforms, the planimetric morphology of which can be either two‐ or three‐dimensional. Experiments were undertaken to examine the processes that transform the bed configuration from two‐dimensional (2D) dunes to three‐dimensional (3D) dunes. A narrowly graded, 500 μm size sand was subjected to a 0·15 m deep, non‐varying mean flow ranging from 0·30 to 0·55 m sec−1 in a 1 m wide flume. Changes in the planimetric configuration of the bed were monitored using a high‐resolution video camera that produced a series of 10 sec time‐lapsed digital images. Image analysis was used to define a critical value of the non‐dimensional span (sinuosity) of the bedform crestlines that divides 2D forms from 3D forms. Significant variation in the non‐dimensional span is observed that cannot be linked to properties of the flow or bedforms and thus appears random. Images also reveal that, once 2D bedforms are established, minor, transient excesses or deficiencies of sand are passed from one bedform to another. The bedform field appears capable of absorbing a small number of such defects but, as the number grows with time, the resulting morphological perturbations produce a transition in bed state to 3D forms that continue to evolve, but are pattern‐stable. The 3D pattern is maintained by the constant rearrangement of crestlines through lobe extension and starving downstream bedforms of sediment, which leads to bifurcation. The experiments demonstrate that 2D bedforms are not stable in this calibre sand and call into question the reliability of bedform phase diagrams that use crestline shape as a discriminator.
Late Pliocene to Holocene platform evolution in northern Belize, and comparison with coeval deposits in southern Belize and the Bahamas
Authors: MAZZULLO S.J. 
Published: September 2010

AbstractLithostratigraphy, depositional facies architecture, and diagenesis of upper Pliocene to Holocene carbonates in northern Belize are evaluated based on a ca 290 m, continuous section of samples from a well drilled on Ambergris Caye that can be linked directly to outcrops of Pleistocene limestone, and of overlying Holocene sediments. Upper Pliocene outer‐ramp deposits are overlain unconformably by Pleistocene and Holocene reef‐rimmed platforms devoid of lowstand siliciclastics. Tectonism controlled the location of the oldest Pleistocene platform margin and coralgal barrier reef, and periodically affected deposition in the Holocene. A shallow, flat‐topped, mostly aggradational platform was maintained in the Holocene by alternating periods of highstand barrier‐reef growth and lowstand karstification, differential subsidence, and the low magnitude of accommodation space increases during highstands. Facies in Pleistocene rocks to the lee of the barrier reef include: (i) outer‐shelf coralgal sands with scattered coral patch reefs; (ii) a shoal–water transition zone comprising nearshore skeletal and oolitic sands amidst scattered islands and tidal flats; and (iii) micritic inner‐shelf deposits. Four glacio‐eustatically forced sequences are recognized in the Pleistocene section, and component subtidal cycles probably include forced cycles and autocycles. Excluding oolites, Holocene facies are similar to those in the Pleistocene and include mud‐mounds, foraminiferal sand shoals in the inner shelf, and within the interiors of Ambergris and surrounding cayes, mangrove swamps, shallow lagoons, and tidal and sea‐marginal flats. Meteoric diagenesis of Pliocene and Pleistocene rocks is indicated by variable degrees of mineralogic stabilization, generally depleted whole‐rock δ18O and δ13C values, and meniscus and whisker‐crystal cements. Differences in the mineralogy and geochemistry of the Pliocene and Pleistocene rocks are attributed to variable extent of meteoric alteration. Dolomitization in the Pliocene carbonates may have begun syndepositionally and continued into the marine shallow‐burial environment. Positive dolomite δ18O and δ13C values suggest precipitation from circulating, near‐normal marine fluids that probably were modified somewhat by methanogenesis. Sedimentologic and diagenetic attributes of the Pliocene–Pleistocene rocks in the study area are similar to those in the Bahamas with which they share a common history of sea‐level fluctuations and climate change.