bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phylogeography of the pool frog Rana (Pelophylax) lessonae in the Italian peninsula and Sicily: multiple refugia, glacial expansions and nuclear–mitochondrial discordance
Authors: Canestrelli Daniele , Nascetti Giuseppe 
Published: July 2008

AbstractAim  To infer the evolutionary history of Rana (Pelophylax) lessonae Camerano within its inferred Quaternary refugial range, and to shed light on the processes that have contributed to shaping the patterns of diversity within the southern European peninsulas.Location  The Italian peninsula south of the Alps and Sicily.Methods  Sequence analysis of a mitochondrial cytochrome b gene fragment in 149 individuals sampled from 25 localities.Results  Three mitochondrial DNA (mtDNA) phylogroups were identified, distributed in northern Italy, the whole Italian peninsula south of the northern Apennines, and Sicily. Syntopy between the northern and peninsular lineages was observed close to the northern Apennines. The northern lineage was the most differentiated, showing a net sequence divergence of 4.8 ± 0.8% with respect to the two others, whereas the net divergence between peninsular and Sicilian lineages was 2.6 ± 0.6%. Analysis of molecular variance (amova) revealed that 93% of the overall variation occurred between these three groups. Historical demographic statistics support a recent expansion for both the northern and peninsular groups, but not for the Sicilian group. In both northern and peninsular Italy, such an expansion was likely to have occurred during the last glaciation.Main conclusions  Our results suggest that a number of microevolutionary processes were involved in shaping the present genetic structure of R. lessonae in Italy. These encompass allopatric differentiations in three distinct Pleistocene refugia, recent population expansions and secondary contacts. Our results, together with some previous work, support (1) the existence of a suture zone in the northern Apennines, and (2) the possibility of population expansions during the last glacial phase, when a vast widening of the lowland floodplain habitats followed sea‐level fall, particularly in northern Italy. When compared with previous analyses of allozyme data, it appears that the peninsular mtDNA lineage has recently replaced the Sicilian one in southern Calabria, and we suggest that this event occurred due to selective introgression. The implications of such an occurrence for the study of factors underlying the patterns of diversity within this southern European biodiversity hotspot are discussed. Taxonomic implications of the results are also evaluated.
Can spatial variation in epiphyte diversity and community structure be predicted from sampling vascular epiphytes alone?
Authors: Affeld K. , Sullivan J. , Worner S. P. , Didham R. K. 
Published: July 2008

AbstractAim  Non‐vascular epiphytes have been largely ignored in studies examining the biotic and abiotic determinants of spatial variation in epiphyte diversity. Our aim was to test whether the spatial patterning of species richness, biomass and community composition across geographic regions, among trees within regions, and among branches within trees is consistent between the vascular and non‐vascular components of the temperate rain forest flora.Location  Coastal lowland podocarp‐broadleaved forests on the west coast of the South Island of New Zealand.Methods  We collected single samples (30 × 25 cm) from 96 epiphyte assemblages located on the inner branches of 40 northern rata (Metrosideros robusta) trees. For each sample, branch characteristics such as branch height, branch diameter, branch angle, branch aspect, and minimum and maximum epiphyte mat depth were recorded. The biomass for each individual epiphyte species was determined.Results  Northern rata was host to a total of 157 species, comprising 32 vascular and 125 non‐vascular species, with liverworts representing 41% of all species. Within epiphyte mats, the average total organic biomass of 3.5 kg m−2 of branch surface area consisted largely of non‐living biomass and roots. Vascular and non‐vascular epiphytes showed strikingly different spatial patterns in species richness, biomass and composition between sites, among trees within sites, and among branches within trees, which could not be explained by the branch structural characteristics we measured. The two plant groups had no significant association in community composition (r = 0.04, P = 0.08). However, the species richness of vascular plant seedlings was strongly linked to the presence/absence of lichens.Main conclusions  Non‐vascular plants contributed substantially to the high species richness and biomass recorded in this study, which was comparable to that of some tropical rain forests. High variability in community composition among epiphyte mats, and very low correlation with any of the environmental factors measured possibly indicate high levels of stochasticity in seed or spore colonization, establishment success or community assembly among branches in these canopy communities. Although we found some evidence that vascular plant seedling establishment was linked to the presence of lichens and the biomass of non‐living components in the epiphyte mats, there was no correlation in the spatial patterning or determinants of species richness between non‐vascular and vascular plants. Consequently, variation in total epiphyte biodiversity could not be predicted from the measurement of vascular plant diversity alone, which highlights the crucial importance of sampling non‐vascular plants when undertaking epiphyte community studies.
The mid‐domain effect matters: simulation analyses of range‐size distribution data from Mount Kinabalu, Borneo
Authors: Grytnes John‐Arvid , Beaman John H. , Romdal Tom S. , Rahbek Carsten 
Published: July 2008

AbstractAim In simulation exercises, mid‐domain peaks in species richness arise as a result of the random placement of modelled species ranges within simulated geometric constraints. This has been called the mid‐domain effect (MDE). Where close correspondence is found between such simulations and empirical data, it is not possible to reject the hypothesis that empirical species richness patterns result from the MDE rather than being the outcome (wholly or largely) of other factors. To separate the influence of the MDE from other factors we therefore need to evaluate variables other than species richness. The distribution of range sizes gives different predictions between models including the MDE or not. Here, we produce predictions for species richness and distribution of range sizes from one model without the MDE and from two MDE models: a classical MDE model encompassing only species with their entire range within the domain (range‐restricted MDE), and a model encompassing all species with the theoretical midpoint within the domain (midpoint‐restricted MDE). These predictions are compared with observations from the elevational pattern of range‐size distributions and species richness of vascular plants.Location Mount Kinabalu, Borneo.Methods The data set analysed comprises more than 28,000 plant specimens with information on elevation. Species ranges are simulated with various assumptions for the three models, and the species simulated are subsequently subjected to a sampling that simulates the actual collection of species on Mount Kinabalu. The resulting pattern of species richness and species range‐size distributions are compared with the observed pattern.Results The comparison of simulated and observed patterns indicates that an underlying monotonically decreasing trend in species richness with elevation is essential to explain fully the observed pattern of richness and range size. When the underlying trend is accounted for, the MDE model that restricts the distributions of theoretical midpoints performs better than both the classical MDE model and the model that does not incorporate geometric constraints.Main conclusions Of the three models evaluated here, the midpoint‐restricted MDE model is found to be the best for explaining species richness and species range‐size distributions on Mount Kinabalu.
Environmental variation has stronger effects than plant genotype on competition among plant species
Authors: Johnson Marc T. J. , Dinnage Russell , Zhou Alice Y. , Hunter Mark D. 
Published: July 2008

SummaryCompetition is a key factor affecting the performance and co‐existence of species. Most ecological research on competition treats species’ populations as phenotypically homogenous. However, plant populations typically contain genetic variation for multiple traits and have the potential to rapidly adapt to changing environments.Recent theoretical and empirical research suggests that such variation and evolution may affect the ecological outcome of competitive interactions. We conducted a series of experiments to test the hypothesis whether genetic variation for competitive traits in a native plant (Oenothera biennis) affects the performance and diversity of competing plant species.In greenhouse and field experiments, the presence ofO. biennisreduced the performance and diversity of neighbouring plant species.In greenhouse experiments, we detected heritable variation inO. biennisfor above‐ground and below‐ground growth, andO. biennisvaried genetically in response to competition, indicating the potential for adaptive evolution in response to selection by competitors.Variation amongO. biennisgenotypes also affected the performance of neighbouring plants in the greenhouse, whereby genetic variation inO. biennisshoot : root ratio explained up to 41% of the variation in the performance of an exotic grass (Bromus inermis).Despite effects ofO. biennisgenotype onB. inermisin the greenhouse, variable soil fertility had a much stronger effect on the grass's performance, and there were no effects ofO. biennisgenotype on neighbouring plants in the field.Synthesis. Our results show that interspecific competition affected the biomass and diversity of plants, but heritable variation in competitive ability ofO. biennisis not expected to affect short‐term ecological dynamics in this system. Nevertheless,O. biennishas the potential to influence co‐existence over longer timescales by adapting to competitors.
aglF, aglG and aglI, novel members of a gene island involved in the N‐glycosylation of the Haloferax volcanii S‐layer glycoprotein
Authors: Yurist‐Doutsch Sophie , Abu‐Qarn Mehtap , Battaglia Francesca , Morris Howard R. , Hitchen Paul G. , Dell Anne , Eichler Jerry 
Published: July 2008

SummaryProteins in all three domains of life can experience N‐glycosylation. The steps involved in the archaeal version of this post‐translational modification remain largely unknown. Hence, as the next step in ongoing efforts to identify components of the N‐glycosylation pathway of the halophilic archaeon Haloferax volcanii, the involvement of three additional gene products in the biosynthesis of the pentasaccharide decorating the S‐layer glycoprotein was demonstrated. The genes encoding AglF, AglI and AglG are found immediately upstream of the gene encoding the archaeal oligosaccharide transferase, AglB. Evidence showing that AglF and AglI are involved in the addition of the hexuronic acid found at position three of the pentasaccharide is provided, while AglG is shown to contribute to the addition of the hexuronic acid found at position two. Given their proximities in the H. volcanii genome, the transcription profiles of aglF, aglI, aglG and aglB were considered. While only aglF and aglI share a common promoter, transcription of the four genes is co‐ordinated, as revealed by determining transcript levels in H. volcanii cells raised in different growth conditions. Such changes in N‐glycosylation gene transcription levels offer additional support for the adaptive role of this post‐translational modification in H. volcanii.
Carbonates within a Pleistocene glaciomarine succession, Yakataga Formation, Middleton Island, Alaska
Authors: JAMES NOEL P. , EYLES CAROLYN H. , EYLES NICHOLAS , HIATT ERIC E. , KURTIS KYSER T. 
Published: July 2008

AbstractUplifted during the 1964 Alaskan earthquake, extensive intertidal flats around Middleton Island expose 1300 m of late Cenozoic (Early Pleistocene) Yakataga Formation glaciomarine sediments. These outcrops provide a unique window into outer shelf and upper slope strata that are otherwise buried within the south‐east Alaska continental shelf prism. The rocks consist of five principal facies in descending order of thickness: (i) extensive pebbly mudstone diamictite containing sparse marine fossils; (ii) proglacial submarine channel conglomerates; (iii) burrowed mudstones with discrete dropstone layers; (iv) boulder pavements whose upper surfaces are truncated, faceted and striated by ice; and (v) carbonates rich in molluscs, bryozoans and brachiopods. The carbonates are decimetre scale in thickness, typically channellized conglomeratic event beds interpreted as resedimented deposits on the palaeoshelf edge and upper slope. Biogenic components originated in a moderately shallow (ca80 m), relatively sediment‐free, mesotrophic, sub‐photic setting. These components are a mixture of parautochthonous large pectenids or smaller brachiopods with locally important serpulid worm tubes and robust gastropods augmented by sand‐size bryozoan and echinoderm fragments. Ice‐rafted debris is present throughout these cold‐water carbonates that are thought to have formed during glacial periods of lowered sea‐level that allowed coastal ice margins to advance near to the shelf edge. Such carbonates were then stranded during subsequent sea‐level rise. Productivity was enabled by attenuation of terrigenous mud deposition during these cold periods via reduced sedimentation together with active wave and tidal‐current winnowing near the ice front. Redeposition was the result of intense storms and possibly tsunamis. These sub‐arctic mixed siliciclastic‐carbonate sediments are an end‐member of the Phanerozoic global carbonate depositional realm whose skeletal attributes first appeared during late Palaeozoic southern hemisphere deglaciation.
Strengthening acceptance for xenotransplantation: the case of attraction effect
Authors: Rubaltelli Enrico , Burra Patrizia , Sartorato Valentina , Canova Daniele , Germani Giacomo , Tomat Silvia , Ancona Ermanno , Cozzi Emanuele , Rumiati Rino 
Published: July 2008

Abstract:  Background:  Despite being still at the experimental level, xenotransplantation may become an effective strategy to overcome the scarcity of human organs. However, at the present time there is considerable resistance to this kind of biomedical technology. The aim of the present study was to identify novel strategies to reduce patients’ negative affective reactions towards xenotransplantation helping them to understand the advantages of xenotransplantation in a more analytical fashion and increase their acceptance for this approach.Methods:  The study was conducted in a group of patients with liver cirrhosis waiting for liver transplantation. They were presented with hypothetical scenarios and asked to choose among either two or three alternative types of donor defined by their species (e.g., livers from humans vs. other species) and availability (low for human donors and high for livers from non‐human species).Results:  Patients were unwilling to accept xenotransplantation if they were presented with livers from humans (chosen by 97.5% of participants) vs. livers from genetically modified pigs (2.5%). On the other hand, a different group of patients was significantly more willing to accept xenotransplantation if they were presented with three different types of donors: respectively, human beings (74.4%), genetically modified pigs (25.6%) and genetically modified dogs. In addition, human livers were judged significantly more attractive than genetically modified livers from pigs, monkeys, dogs, or sheep and pig livers were rated as significantly more attractive than livers from monkeys, dogs, or sheep (for all comparisons P < 0.01).Conclusions:  These results demonstrate that paradigms from other fields, like decision‐making, might help to communicate more effectively the potential of xenotransplantation, modulating patients’ affective reactions and allowing them to understand the potential strengths of this biomedical technology.
Toward evolutionary graphs with two sexes: a kin selection analysis of a sex allocation problem
Authors: WILD GEOFF 
Published: July 2008

AbstractEvolutionary graphs are used to model the effects of spatial and social structure in social evolutionary problems (e.g. evolutionary games). Recent work has highlighted the fact that evolution on graphs can be understood using kin selection theory. This paper shows how one can use kin selection to study evolutionary graphs inhabited by a diploid sexual organism by means of a simple example. Specifically, we study the well‐known sex allocation problem of how best to divide a fixed amount of effort between the production of sons on the one hand and the production of daughters on the other. Like many previous studies, we identify equal investment in sons and daughters as the only phenotype favoured by selection. Our analysis also highlights the advantages and disadvantages of applying kin selection to the study of evolutionary graphs.
Multiple parasites mediate balancing selection at two MHC class II genes in the fossorial water vole: insights from multivariate analyses and population genetics
Authors: TOLLENAERE C. , BRYJA J. , GALAN M. , CADET P. , DETER J. , CHAVAL Y. , BERTHIER K. , RIBAS SALVADOR A. , VOUTILAINEN L. , LAAKKONEN J. , HENTTONEN H. , COSSON J.‐F. , CHARBONNEL N. 
Published: July 2008

AbstractWe investigated the factors mediating selection acting on two MHC class II genes (DQA and DRB) in water vole (Arvicola scherman) natural populations in the French Jura Mountains. Population genetics showed significant homogeneity in allelic frequencies at the DQA1 locus as opposed to neutral markers (nine microsatellites), indicating balancing selection acting on this gene. Moreover, almost exhaustive screening for parasites, including gastrointestinal helminths, brain coccidia and antibodies against viruses responsible for zoonoses, was carried out. We applied a co‐inertia approach to the genetic and parasitological data sets to avoid statistical problems related to multiple testing. Two alleles, Arte‐DRB‐11 and Arte‐DRB‐15, displayed antagonistic associations with the nematode Trichuris arvicolae, revealing the potential parasite‐mediated selection acting on DRB locus. Selection mechanisms acting on the two MHC class II genes thus appeared different. Moreover, overdominance as balancing selection mechanism was showed highly unlikely in this system.
QTL mapping of inbreeding‐related cold sensitivity and conditional lethality in Drosophila melanogaster
Authors: VERMEULEN C. J. , BIJLSMA R. , LOESCHCKE V. 
Published: July 2008

AbstractInbreeding depression is a central theme within genetics, and is of specific interest for researchers within evolutionary and conservation genetics and animal and plant breeding. Inbreeding effects are thought to be caused by the joint expression of conditional and unconditional deleterious alleles. Whenever the expression of deleterious alleles is conditional, this can result in extreme environmental sensitivity in certain inbred lineages. Analysis of conditional lethal effects can reveal some of the loci that are sensitive to inbreeding. We performed a QTL (quantitative trait locus) mapping study of inbreeding‐related and conditionally expressed lethality in Drosophila melanogaster. The lethal effect was triggered by exposure to a cold shock. We used a North Carolina crossing Design 3 to establish the mapping population, as well as to estimate the average dominance ratio and heritability. We found two QTL on the major autosomes carrying recessive lethals that caused male mortality, one of which also affected female mortality. More detailed study of these loci will provide information on the mechanistic basis and environmental sensitivity of inbreeding depression.
The impact of parasite dispersal on antagonistic host–parasite coevolution
Authors: VOGWILL T. , FENTON A. , BROCKHURST M. A. 
Published: July 2008

AbstractCoevolving populations of hosts and parasites are often subdivided into a set of patches connected by dispersal. Higher relative rates of parasite compared with host dispersal are expected to lead to parasite local adaptation. However, we know of no studies that have considered the implications of higher relative rates of parasite dispersal for other aspects of the coevolutionary process, such as the rate of coevolution and extent of evolutionary escalation of resistance and infectivity traits. We investigated the effect of phage dispersal on coevolution in experimental metapopulations of the bacterium Pseudomonas fluorescens SBW25 and its viral parasite, phage SBW25Φ2. Both the rate of coevolution and the breadth of evolved infectivity and resistance ranges peaked at intermediate rates of parasite dispersal. These results suggest that parasite dispersal can enhance the evolutionary potential of parasites through provision of novel genetic variation, but that high rates of parasite dispersal can impede the evolution of parasites by homogenizing genetic variation between patches, thereby constraining coevolution.
Synergistic effect of drought and chestnut blight (Cryphonectria parasitica) on growth decline of European chestnut (Castanea sativa)
Authors: Waldboth M. , Oberhuber W. 
Published: July 2008

SummaryThe chestnut blight fungus [Cryphonectria parasitica (Murill) Barr] has threatened European chestnut stands (Castanea sativa Mill.) in the 20th century, but infected trees recovered because of the appearance of hypovirulent strains. However, within a dry inner Alpine valley (Italy), blight‐infected C. sativa showing various degrees of crown dieback and dead trees were found. We conducted a dendroecological analysis to retrospectively evaluate a possible synergistic effect of blight infection in the early 1970s and climate stress on the growth decline of C. sativa. In the Eisack Valley (Italy), where annual precipitation is <700 mm, increment cores were taken from blight‐infected C. sativa (n = 103) showing different levels of decline symptoms, i.e. extent of crown dieback (healthy, moderate, severe), and from dead trees. Ring width and basal area increment (BAI) chronologies were developed based on dendroecological methods. Growth–climate relationships were explored using response function analysis and Pearson correlation coefficients. Major findings of our study were: (i) C. sativa growth is limited by low precipitation from December to February and high temperatures in June, (ii) BAI of all vitality classes except healthy trees shows a decreasing trend since 1980; and (iii) a severe drought in 1996 accelerated growth decline and caused death of infected C. sativa individuals. Because of the strong influence of climate on radial tree growth within the study area and observed divergent growth trends in selected vitality classes after infestation by hypovirulent C. parasitica strains in the early 1970s, we conclude that although blight infection is a prerequisite for observed growth declines, soil water availability in the years of drought strongly affects susceptibility to tree death.