bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing spatial variation in browsing history by means of fraying scars
Authors: Vila Bruno , Guibal Frédéric , Torre Franck , Martin Jean‐Louis
Published: May 2004

Aim  We used fraying scars to understand spatial variation in browsing history. Information on browsing history is an essential background in studies on the long‐term effect of deer browsing on the flora and fauna and of its variation in space.

Location  We focused on two small neighbouring islands of Haida Gwaii (British Columbia, Canada), Reef Island and South‐Skedans Island, colonized by introduced black‐tailed deer (Odocoileus hemionus sitkensis).

Methods  We searched for sites where trees with fraying scars were clustered. We studied the trees that deer selected (species, size) and the characteristics of scars (number, position, size). Using a cross‐dating procedure, we dated fraying scars with dendrochronology, obtaining an accurate estimate of the year the scar was formed.

Results  On Reef Island, Thuja plicata was the tree species chosen for fraying. On South‐Skedans Island, where Thuja plicata is missing, deer chose Salix sp. and Alnus rubra. Deer chose only trees with a circumference of less than 50 cm. About two to three fraying scars were recorded per tree. All of them extended between 30–40 and 70–80 cm from the ground and were between 5 and 6 cm in width. On Reef Island, 95% of the scars were formed during the last 50 years. On South‐Skedans Island, 95% were formed over the last 10 years. Age distribution of scars showed a constant increase of the number of scars over time. It indicated that deer had colonized Reef Island 53 years prior to this study but were absent or rare on South‐Skedans Island until 13 years prior to this study.

Main conclusions  These results indicate different colonization dates and thus different length of browsing histories for the islands studied and provide the historical background necessary to analyse the involvement of deer in the current differences in the flora and fauna observed between islands.
Seed removal by small mammals, birds and ants in semi‐arid Chile, and comparison with other systems
Authors: Kelt Douglas A. , Meserve Peter L. , Gutiérrez Julio R.
Published: May 2004

Aim  This study aims to evaluate the relative importance of birds, small mammals, and ants as seed predators at a semi‐arid site in northern Chile.

Location  Northern Chile, in Parque Nacional Bosque Fray Jorge (30°41′ N, 71°40′ W, c. 80 m elevation).

Methods  We studied the relative abilities of birds, small mammals, and ants to find and remove millet seeds either singly (i.e. background seed removal) or in bulk. Single seeds were set in shallow depressions in Plexiglas trays which were established in long and arbitrary transects, and were available either to birds (diurnally) or small mammals (nocturnally) or were covered by hardware cloth and therefore available only to ants. Bulk removal was evaluated with seeds in Petri dishes that also were established in long and arbitrary transects, and trays were either open diurnally (birds) or nocturnally (small mammals); a third set of trays was covered with hardware cloth cages to excluded vertebrates, and ants were given access to Petri dishes with twigs that were arranged across the edge of the dishes. All experiments lasted four days and nights, and trays and dishes were checked and replenished as needed in the morning and evening. In the former study vertebrate consumption was determined as the mean number of seeds removed from trays (within a given transect) minus the number removed from ant‐only trays. Because ants were rarely seen in vertebrate access Petri dishes, however, we did not correct consumption there. Treatments were compared using repeated measures mixed model analysis of variance. In addition to evaluating patterns within this community, we compared our results against those obtained in similar studies in various arid regions.

Results  Diurnal seed consumption was significantly greater than nocturnal seed consumption, which in turn was significantly greater than consumption by ants. Diurnal consumption was highly seasonal, evidently corresponding to the seasonal arrival and departure of migratory birds. In general, South American sites exhibit much lower levels of seed predation than sites in the northern hemisphere, but removal at our site appears to be much greater and more strongly avian‐dominated than at other sites in South America. Our results are consistent with predictions based on a hypothesis relating precipitation to seed predictability.

Main conclusions  Both birds and small mammals were much more important seed consumers at our site than elsewhere in South America, whereas ants have been relatively unimportant at all South American sites studied to date. Although the dominant seed consumers differ across sites, overall levels of seed removal appear similar in South America and Australia, and substantially lower than reported from sites in the northern hemisphere and Africa.
Null model analysis of communities on gradients
Authors: Sanderson James G.
Published: May 2004

Aim  I employed a novel null model and metric to uncover unusual species co‐occurrence patterns in a herpetofaunal assemblage of 49 species collected at discrete elevations along a gradient.

Location  Mount Kupe, Cameroon.

Methods  Using a construction algorithm that started from a matrix of 0s, a sample null space of 25,000 unique null matrices was generated by simultaneously conserving (1) the number of occurrences of each species, (2) site richness and (3) species range spans derived from the observed incidence matrix. I then compared the number of times each pair of confamilial species co‐occurred in the null space with the same number derived from the observed incidence matrix. Two cases dealing with embedded absences in species ranges were tested: (1) embedded absences were maintained, and (2) embedded absences were assumed to be sampling omissions and were replaced by presences.

Results  In the observed absence/presence assemblage there were 147 possible confamilial species pairs. Therefore, 5% or eight were expected by chance alone to have co‐occurrence patterns that differed from chance expectations by chance alone. Of these confamilial species pairs, 38 were congeneric and so 5% or two were expected to differ from chance expectations. For case (1) 16, and for case (2) 17 confamilial species pairs’ co‐occurrence patterns differed significantly from chance expectations. For case (1) nine congeneric species pairs, and for case (2) 10 congeneric pairs differed significantly from chance expectations. For case (1) four, and for case (2) five congeneric species pairs formed checkerboards (patterns of mutual exclusion). Results from case (1) were a proper subset of case (2) indicating that sampling omissions did not alter greatly the results.

Main conclusions  I have demonstrated that null models are valuable tools to analyse ecological communities provided that proper models are employed. The choice of the appropriate null space to analyse distributions is critical. The null model employed to analyse birds on islands of an archipelago can be adapted to analyse species along gradients provided an additional range constraint is added to the null model. Moreover, added precision to results can be obtained by analysing each species pair separately, particularly those in the same family or genus, as opposed to applying a community‐wide metric to the faunal assemblage. My results support some of the speculations of previous authors who were unable to demonstrate their suspicions analytically.
A new land‐cover map of Africa for the year 2000
Authors: Mayaux Philippe , Bartholomé Etienne , Fritz Steffen , Belward Alan
Published: May 2004

Aim  In the framework of the Global Land Cover 2000 (GLC 2000), a land‐cover map of Africa has been produced at a spatial resolution of 1 km using data from four sensors on‐board four different Earth observing satellites.

Location  The map documents the location and distribution of major vegetation types and non‐vegetated land surface formations for the entire African continent plus Madagascar and the other surrounding islands.

Methods  The bulk of these data were acquired on a daily basis throughout the year 2000 by the VEGETATION sensor on‐board the SPOT‐4 satellite. The map of vegetation cover has been produced based upon the spectral response and the temporal profile of the vegetation cover. Digital image processing and geographical information systems techniques were employed, together with local knowledge, high resolution imagery and expert consultation, to compile a cartographic map product. Radar data and thermal sensors were also used for specific land‐cover classes.

Results  A total of 27 land cover categories are documented, which has more thematic classes than previously published land cover maps of Africa contain. Systematic comparison with existing land cover data and 30‐m resolution imagery from Landsat are presented, and the map is also compared with other pan‐continental land cover maps. The map and digital data base are freely available for non‐commercial uses from http://www.gvm.jrc.it/tem/africa/products.htm

Main conclusions  The map improves our state of knowledge of the land‐cover of Africa and presents the most spatially detailed view yet published at this scale. This first version of the map should provide an important input for regional stratification and planning purposes for natural resources, biodiversity and climate studies.
Molecular biogeography of the arctic‐alpine disjunct burnet moth species Zygaena exulans (Zygaenidae, Lepidoptera) in the Pyrenees and Alps
Authors: Schmitt Thomas , Hewitt Godfrey M.
Published: May 2004

Aim  The phylogeography of ‘southern’ species is relatively well studied in Europe. However, there are few data about ‘northern’ species, and so we studied the population genetic structure of the arctic‐alpine distributed burnet moth Zygaena exulans as an exemplar.

Location and methods  The allozymes of 209 individuals from seven populations (two from the Pyrenees, five from the Alps) were studied by electrophoresis.

Results  All 15 analysed loci were polymorphic. The mean genetic diversities were moderately high (A: 1.99; He: 11.5; P: 65%). Mean genetic diversities were significantly higher in the Alps than in the Pyrenees in all cases. FST was 5.4% and FIS was 10%. Genetic distances were generally low with a mean of 0.022 between large populations. About 62% of the variance between populations was between the Alps and the Pyrenees. The two samples from the Pyrenees had no significant differentiation, whereas significant differentiation was detected between the populations from the Alps (FST = 2.8%, P = 0.02).

Main conclusion  Zygaena exulans had a continuous distribution between the Alps and the Pyrenees during the last ice age. Most probably, the species was not present in Iberia, and the samples from the Pyrenees are derived from the southern edge of the glacial distribution area and thus became genetically impoverished. Post‐glacial isolation in Alps and Pyrenees has resulted in a weak genetic differentiation between these two disjunct high mountain systems.
Correlates of species richness in North American bat families
Authors: Patten Michael A.
Published: May 2004

Aim  A near universal truth in North America is that species richness increases from the Arctic Circle to the Central American tropics. Latitude is regarded as a major explanatory variable in species density, although it is only a surrogate for underlying ecological variables. I aimed to elucidate those underlying ecological variables that are associated with variation in bat species richness across the entire North American continent, providing a portrait of the macroecology of the order Chiroptera and its familial components.

Methods  I determined the number of bat species recorded for every state in Mexico and the United States, every province or territory in Canada, and every country in Central America. For each of these entities (n = 99), I also gathered basic data on mean annual precipitation, variation across the year (July vs. January) in mean temperature, mean January temperature, range in elevation (topographic relief), per cent vegetative cover and median latitude. Using a variety of linear regression and model‐fitting techniques, I analysed the strength and direction of the relationship between species richness and environmental variables for the order Chiroptera as a whole and separately for each of four familial groups: Molossidae (free‐tailed bats), Phyllostomidae (New World leaf‐nosed bats), Vespertilionidae (evening bats), and a set of six families (the Desmodontidae, Emballonuridae, Furipteridae, Natalidae, Noctilionidae, and Thyropteridae) represented in North America relatively poorly.

Results and main conclusions  Save for the Vespertilionidae, species richness of bats increased towards the Panamanian Isthmus. The Phyllostomidae and the set of miscellaneous families are particularly speciose in tropical Central America, with many fewer species occurring through subtropical Mexico into (in some cases) the southernmost United States. The Molossidae extends farther north, sparingly into the middle of the United States. Species density of the Vespertilionidae peaks in central and western Mexico and the southernmost United States, declining south through tropical southern Mexico and Central America and north through the central United States into Canada. Annual precipitation, January temperature, and topography are good predictors of species richness in the Chiroptera and the Molossidae, precipitation, topography, and temperature range in the Phyllostomidae, January temperature and topography in the Vespertilionidae, and precipitation alone in the collection of families. Vegetative cover explained little variation in the Chiroptera as a whole or in any family. After accounting for the effects of the environmental variables, latitude explained an insignificant amount of the residual variation in species richness. Bat families differ in their ecology, so studies of bat biogeography in North America may be misleading if they are examined only at the ordinal level.
Genetic variation and geographical structure of five mouse‐sized opossums (Marsupialia, Didelphidae) throughout the Guiana Region
Authors: Steiner Cynthia , Catzeflis François M.
Published: May 2004

Aim and location  To study the patterns of genetic variation and geographical structure of five forest‐dwelling didelphid species distributed throughout the Guiana Region (Marmosops parvidens, M. pinheiroi, Monodelphis brevicaudata, Marmosa murina, Micoureus demerarae) and place the results for wide‐ranging species (M. murina, M. demerarae) in the broader geographical context of the rest of the taxon ranges based on published data.

Methods  Variation in the mitochondrial cytochrome b gene were analysed in order to assess intra‐specific sequence divergence as well as haplotypic and nucleotide diversity among populations. Relationships between haplotypes were inferred by cladistic (maximum parsimony) and probabilistic (maximum likelihood) approaches, allowing comparisons between tree topologies and patterns of populations geographical distribution.

Results  Phylogenetic analysis of the Guiana Region populations suggest the lack of common patterns of geographical structure among mouse‐sized opossums except for both Marmosops species. Marmosops parvidens and M. pinheiroi showed individuals from Surinam strongly related with those from Guyana, and haplotypes from French Guiana having a basal position. Concerning Micoureus demerarae, haplotypes from Venezuela were positioned as ancestral, in contrast with Monodelphis brevicaudata, whose French Guiana haplotypes were clustered in a basal position. No evidence of geographical structure was observed for Marmosa murina. Genetic variation within Guiana Region populations fluctuated between 1% for M. murina and 7% in the case of M. brevicaudata. Regarding the widely distributed species, phylogeographical structure at the scale of the Amazon Basin suggests that Guiana Region populations are the sister group of south‐eastern Amazonian and Atlantic Forest populations, thus resulting in an eastern clade well separated from the western Amazonian regions.

Main conclusions  Monophyly of mouse‐sized opossums haplotypes over the Guiana Region confirms the presence of a well‐differentiated zoogeographical area relative to other Amazonia bioregions. Low genetic diversity among Guiana Region samples suggests a relatively recent origin of populations dating from later Miocene and Pleistocene periods. Moreover, nucleotide and haplotypic diversity values suggest an evolutionary scenario of rapid population growth and dispersal over the Guiana territory, from an ancestral population with small effective size. Dispersal events – rather than vicariance – seem to be responsible for the present genetic and phylogeographical patterns observed in the Guiana Region.
The effect of a dietary preload on estimation of usual food portion size by photograph in female volunteers
Authors: Beasley L. J. , Hackett A. F. , Maxwell S. M. , Stevenson L.
Published: May 2004

Background  The aim of this study was to investigate whether a subject's level of satiety influences perception of their usual portion size.

Methods  A total of 62 school children were recruited for the pilot study. Half of the group assessed food photographs for their usual portion size before lunch, and half after lunch. For the main study, 55 female students were recruited to test within‐subject variation in perception of usual portion size before and after consuming a preload.

Results  Significant differences in perception of portion size were found for four of the six foods used.

Conclusion  Some subjects’ perception of their usual portion size was influenced by their level of satiety. Further study is needed to investigate this using a wider variety of food photographs and an alternative preload.
Perceived role of fibre in a healthy diet among Finnish consumers
Authors: Lyly M. , Soini E. , Rauramo U. , Lähteenmäki L.
Published: May 2004

Objective  The aim was to study how Finnish consumers perceive the role of fibre in the diet, which foods are regarded as good sources of fibre and the relationship between the respondents’ self‐estimated fibre intake and their measured intake.

Methods  A semistructured interview was conducted with 125 volunteers, including a background information questionnaire and an easy‐to‐use self‐administered paper‐and‐pencil form estimating fibre intake.

Results  According to the self‐administered form about half of the respondents had adequate fibre intake. Among those who estimated their fibre intake as adequate/maybe adequate, only 61% belonged to the highest fibre intake group. Most of the respondents defined their diet as being healthy. The key elements for a healthy diet were ‘vegetables’, ‘low in fat’, ‘fruit and berries’ and ‘variety’. Only 5% of the respondents mentioned fibre spontaneously here. However, fibre was considered important for health because of its effect on bowel function and general well‐being. The recommended intake of fibre could not be described in nutritional terms, but respondents could identify relevant sources of fibre in the diet.

Conclusion  Finnish consumers considered fibre important for health and could recognize the sources of fibre correctly although they did not mention it spontaneously as a part of a healthy diet.
Retrospective analysis of the impact of a low glycaemic index diet on hospital stay following coronary artery bypass grafting: a hypothesis
Authors: Patel V. C. , Aldridge R. D. , Leeds A. , Dornhorst A. , Frost G. S.
Published: May 2004

Objective  Glucose tolerance and insulin resistance influence medical outcome in subjects with coronary artery disease, these metabolic parameters also influence general perioperative surgical outcome. We hypothesize that glucose tolerance and insulin resistance can be favourably modified by reducing the glycaemic index of the diet.

Design  The present study is a retrospective analysis of a low and high glycaemic index diet on glucose tolerance, insulin resistance and perioperative outcome, as assessed by the length of hospital stay following coronary artery bypass surgery. Thirty‐five adults awaiting bypass surgery were randomized, for the 4 weeks prior to surgery, to either a low glycaemic index diet (17 subjects) or high glycaemic index diet (18 subjects). Glucose and insulin responses during a 75 g oral glucose tolerance test were assessed before and after dietary intervention and insulin‐mediated glucose uptake was assessed in isolated adipocytes obtained at surgery.

Results  The patients who consumed a low glycaemic diet had improved glucose tolerance and significantly greater in vitro adipocyte insulin sensitivity at the time of surgery compared with the high glycaemic diet group (78.87 ± 10.64% versus 41.11 ± 7%, respectively). The total length of stay in the patients on the low glycaemic diet was less than patients consuming the high glycaemic diet (7.06 ± 0.38 days versus 9.53 ± 1.44 days, P < 0.5).

Conclusion  This study provides further support that carbohydrate and fat metabolism influence cardiac outcome and provides new evidence that dietary modification prior to coronary artery bypass surgery can shorten hospital stay.
Intentional mis‐reporting of food consumption and its relationship with body mass index and psychological scores in women
Authors: Lara J. J. , Scott J. A. , Lean M. E. J.
Published: May 2004

Background  The reasons for mis‐reporting food consumption warrant investigation.

Objective  To document intention to mis‐report food consumption and its associations with psychological measures in women.

Design  A total of 184 female volunteers aged 18–65 years, comprising 50 seeking help in primary care to lose weight with a body mass index (BMI) ≥30 kg m−2 (obese‐clinical group) and 134 nurses (nonclinical groups) (BMI <25 kg m−2, n = 52; BMI 25–29.9 kg m−2, n = 45; BMI ≥30 kg m−2, n = 37) were studied. A questionnaire was administered containing three psychological tests (self‐esteem, psychological well‐being and Stunkard's three‐factor eating questionnaire) and new items to address food intake mis‐reporting.

Results  Overall, 68% of participants declared an inclination to mis‐report (64% nonclinical, 78% clinical). Inclination to under‐report was 29, 33 and 51% in the three nonclinical groups; and 46% among the obese clinical patients. Among the same groups, inclination to over‐report were 39, 29, 11 and 32%. After adjusting for social deprivation and BMI, women inclined to mis‐report had higher hunger (P = 0.008) and disinhibition (P = 0.005) scores than those intending to report accurately. These variables were associated with current dieting, frequency of dieting, self‐reported bingeing and dissatisfaction with body weight.

Conclusions  These findings indicate that intentional under‐reporting and over‐reporting of food consumption are common in women of all BMI categories and are associated with eating behaviour. Current dieting, frequency of dieting in the past, self‐reported bingeing and dissatisfaction with body weight seem to mediate this relationship.
Effect of changing to a self‐selected vegetarian diet on anthropometric measurements in UK adults
Authors: Phillips F. , Hackett A. F. , Stratton G. , Billington D.
Published: May 2004

Background  Vegetarians are often a little leaner compared with nonvegetarians and suffer less from obesity and its associated complications than nonvegetarians. Whether this is because of not eating meat specifically is unclear.

Objective  We investigated whether changing to a self‐selected vegetarian diet resulted in changes to anthropometric measurements.

Design  Subjects (n = 33; seven males and 26 females) who were in the earliest stages of becoming vegetarian were observed for 6 months. Data on dietary intake, using a 3‐day estimated dietary diary, and body composition were obtained at baseline and after 6 months of following a self‐selected vegetarian diet.

Results  Dietary calculations showed that on changing to a self‐selected vegetarian diet, there was a significant reduction (P < 0.05) in energy intake (8.9 MJ day−1 versus 8.1 MJ day−1), and in the proportion of energy from saturated fatty acids (12.9% versus 11.3%) and a significant increase (P < 0.05) in the proportion of energy from carbohydrates (44.9% versus 47.5%) and in intake of nonstarch polysaccharides (NSP) (1.6 g MJ−1 versus 2.0 g MJ−1). Significant reductions in mid‐upper arm circumference, calculated body fat, biceps and triceps skinfolds and waist and hip circumferences were observed. No reduction in body weight was observed.

Conclusion  The findings of our study suggest that significant dietary changes, helping people to conform more closely to current dietary recommendations, occurred when people became vegetarian. In this study we did not find any significant change in body weight, but significant reductions were observed in skinfold thickness and waist : height ratio which imply that on changing to a self‐selected vegetarian diet, the subjects became leaner.
Nutrition in the community – an exploratory study of oral nutritional supplements in a health board area in Ireland
Authors: Loane D. , Flanagan G. , de Siún A. , Mc Namara E. , Kenny S.
Published: May 2004

Background  A review of the General Medical (Payments) Scheme data in the Midland Health Board (MHB) Ireland identified a spend of just over € 0.5 million on enteral nutritional supplements (oral and tube feeds) in an 11‐month period in 1998 [General Medical Services (Payments) Board, 1998, MHB Clinical Nutritional Products: January–December 1998, Dublin]. In 2000, a figure of €5 million was reported as the annual spend (oral and tube feeds) [General Medical Services (Payments) Board, 2000, MHB Clinical Nutritional Products: January–December 2000, Dublin].

Research has shown that a high proportion of Oral Nutritional Supplements (ONS) are inappropriately prescribed by primary care practitioners (Gall et al., 2001).

The role of General Practitioners (GPs) and Public Health Nurses (PHNs) in prescribing ONS to patients aged 65 years and older was examined, as they are directly involved in the delivery of primary health care.

Aim  (i) Assess current trends, decision‐making processes and monitoring procedures in the use of ONS for older patients in the community. (ii) Identify whether nutritional assessments and appropriate nutritional criteria are standard practice in determining selection of ONS.

Methods  A study was conducted among 99 GPs and 120 PHNs in the MHB. All GPs were selected to participate and 50% (60) of PHNs were randomly selected. A telephone questionnaire was administered to each subject over a 2‐week period.

Results  Both GPs (78%) and PHNs (47%) reported that their prescription of/recommendations for ONS had increased in the last 4 years. None conducted a full nutritional assessment, but 25% of PHNs used a Nutrition Screening Tool when trying to ascertain whether a patient requires an ONS. Only 19.6% of GPs and 6.8% of PHNs surveyed were aware of the calorie content of a standard 200 mL ONS (sip‐feed). In addition, a very significant proportion of both GPs and PHNs do not appear to give appropriate dietary advice to patients who may be at risk of malnutrition. Only 55% of GPs stated that they would specifically review a patient's ONS prescription. All GPs said that they would not conduct a full nutritional assessment at the review appointment.

Conclusion  The results of this study raise concerns as to the appropriateness of current ONS prescription and monitoring in the community. They also highlight the need for further intervention in the primary care setting in order to ensure that elderly malnourished patients are detected, treated and monitored in an appropriate and cost‐effective manner.
Manipulating angiogenesis in medicine
Authors: Carmeliet Peter
Published: May 2004

Blood vessels nourish organs with vital nutrients and oxygen and, thus, new vessels form when the embryo needs to grow or wounds are to heal. However, forming new blood vessels is a complex and delicate process, which, unfortunately, is often derailed. Thus, when insufficient vessels form, the tissue becomes ischaemic and stops to function adequately. Conversely, when vessels grow excessively, malignant and inflamed tissues grow faster. It is now becoming increasingly evident that abnormal vessel growth contributes to the pathogenesis of numerous malignant, ischaemic, inflammatory, infectious and immune disorders. With an in‐depth molecular understanding, we should be better armamented to combat such angiogenic disorders in the future. That such therapeutic strategies might change the face of medicine is witnessed by initial evidence of success in the clinic.
Combining paternally and maternally inherited mitochondrial DNA for analysis of population structure in mussels
Authors: Krebs Robert A.
Published: May 2004

Sequence divergence for a fragment of the 16S rRNA gene was compared to identify the advantages in using mitochondrial genes that descend separately through the female and male lineages to examine population structure. The test compared divergence among four local species of freshwater mussels (Unionidae) and was extended to multiple populations of one species, Pyganodon grandis. For the same gene, the male‐inherited sequences diverged at a faster rate, producing longer branch lengths in the phylogenies. Of particular use were sequences extracted from P. grandis populations from the southern region of the Lake Erie watershed (Ohio, USA); five male‐inherited haplotypes were found. Only one change was observed in the female‐inherited form in this region. Therefore, more rapid evolution has occurred in the male form of the gene, and this form provided stronger evidence of geographical isolation among populations. A combination of analyses on haplotypes derived through males and females creates complementary opportunities to identify evolutionary relationships caused by drift and migration in mussels.
Genetic diversity in Tetrachaetum elegans, a mitosporic aquatic fungus
Authors: Laitung Beryl , Chauvet Eric , Feau Nicolas , Fève Katia , Chikhi Lounès , Gardes Monique
Published: May 2004

Tetrachaetum elegans Ingold is a saprobic aquatic hyphomycete for which no sexual stage has yet been described. It occurs most commonly during the initial decay of tree leaves in temperate freshwater habitats and typically sporulates under water. Dispersal of the aquatic fungus takes place primarily in the water column and has a large passive component. Differences in substrate composition (e.g. quality of leaf litter) may also play a role in the distribution of different species or genotypes. The population genetic structure of T. elegans was studied using amplified fragment length polymorphism (AFLP) multilocus fingerprints. The populations were isolated from the leaf litter of three different tree genera, sampled in nine streams distributed throughout a mixed deciduous forest. Molecular markers were developed for 97 monosporic isolates using four selective primer pairs. A total of 247 fragments were scored, of which only 32 were polymorphic. Significant stream differentiation was detected for the isolates considered in this study. Analysis of molecular variance revealed that 20% of the genetic variation observed was the result of differences between streams. No correlation between genetic and geographical distances was found but a few multilocus genotypes were observed in different locations. Altogether these results suggest that environmental barriers play a role in the population structure of this aquatic fungus. No clear‐cut effect of leaf litter composition on genetic variation could be demonstrated. Finally, tests of linkage disequilibrium between the 32 polymorphic AFLP loci as well as simulations did not provide a final answer regarding clonality in T. elegans. Indeed, it was possible to reject linkage equilibrium at different sampling levels and show that full linkage was unlikely.
Habitat age, breeding system and kinship in the antFormica fusca
Authors: Hannonen Minttumaaria , Helanterä Heikki , Sundström Liselotte
Published: May 2004

In polygyne ants (multiple queens per colony) factors that affect the distribution and survival of queens may play a key role in shaping the population‐wide mating system and colony kin structure. The aim of this paper was to study the breeding system in two populations of different age in the facultatively polygyne antFormica fusca.Both the observed numbers of queens, and the relatedness patterns among queens, workers and colony fathers were compared in two adjacent populations (ages 17 years and > 100 years) in Southern Finland. The results showed that both the mating system and colony kin structure differed between the study populations. In the old population the relatedness among workers, queens and colony fathers was high. The queens were also related to their mates, resulting in significant inbreeding in workers, but not in queens. Finally, the number of queens per colony fluctuated between years, suggesting queen turnover, and nest‐mate queens shared their reproduction unequally (reproductive skew). In the younger population relatedness among queens and workers was lower than in the old population, and the colony fathers were unrelated. Furthermore, inbreeding was absent, and no conclusive evidence was found for reproductive skew among nest‐mate queens. Finally, the number of queens per colony appeared more stable between years, although queen turnover occurred also in this population. The observed differences in dispersal and mating behaviour are discussed in the light of a potential connection between population age and habitat saturation.
Genetic evidence for sex‐biased dispersal in resident bottlenose dolphins (Tursiops aduncus)
Authors: Möller Luciana M. , Beheregaray Luciano B.
Published: May 2004

In most mammals males usually disperse before breeding, while females remain in their natal group or area. However, in odontocete cetaceans behavioural and/or genetic evidence from populations of four species indicate that both males and females remain in their natal group or site. For coastal resident bottlenose dolphins field data suggest that both sexes are philopatric to their natal site. Assignment tests and analyses of relatedness based on microsatellite markers were used to investigate this hypothesis in resident bottlenose dolphins, Tursiops aduncus, from two small coastal populations of southeastern Australia. Mean corrected assignment and mean relatedness were higher for resident females than for resident males. Only 8% of resident females had a lower probability than average of being born locally compared to 33% of resident males. Our genetic data contradict the hypothesis of bisexual philopatry to natal site and suggest that these bottlenose dolphins are not unusual amongst mammals, with females being the more philopatric and males the more dispersing sex.
Prevalence of interspecific hybrids amongst asexual fungal endophytes of grasses
Authors: Moon C. D. , Craven K. D. , Leuchtmann A. , Clement S. L. , Schardl C. L.
Published: May 2004

Epichloë endophytes are fungal symbionts of grasses that span a continuum including asexual mutualists that are vertically transmitted, obligately sexual pathogens that are horizontally transmitted, and mixed‐strategy symbionts with both mutualistic and pathogenic capabilities. Here we show that processes of genome evolution differ markedly for the different symbiont types. Genetic and phylogenetic analysis was conducted of a broad taxonomic, ecological and geographical sample of sexual and asexual isolates, in which were identified and sequenced alleles of genes for β‐tubulin (tub2) and translation elongation factor 1‐α (tef1), and microsatellite alleles were identified by length polymorphisms. The majority of asexual isolates had two or three alleles of most loci, but every sexual isolate had only single alleles for each locus. Phylogenetic analysis of tub2 and tef1 indicated that in all instances of multiple alleles in an isolate, the alleles were derived from different sexual species. It is concluded that, whereas horizontally transmissible species had haploid genomes and speciation occurred cladistically, most of the strictly seedborne mutualists were interspecific hybrids with heteroploid (aneuploid or polyploid) genomes. Furthermore, the phylogenetic evidence indicated that, in at least some instances, hybridization followed rather than caused evolution of the strictly seedborne habit. Therefore, the abundance of hybrid species among grass endophytes, and their prevalence in many host populations suggests a selective advantage of hybridization for the mutualistic endophytes.
Ecological determinants of genetic diversity in an expanding population of the shrub Myrica cerifera
Authors: Erickson David L. , Hamrick J. L. , Kochert Gary D.
Published: May 2004

The ecological mechanisms that contribute to the acquisition of genetic diversity in an expanding population of the shrub, Myrica cerifera, on an island habitat were investigated. Genealogical reconstruction was used to assess the contribution of early reproductive colonists to subsequent recruitment. In addition, through determination of parentage, the source of recruiting seedlings was identified and the contribution of seed and pollen dispersal into the colonizing sites was inferred. The relative contribution of different sources of gene flow was determined directly and an investigation was made into how variability in breeding patterns may have contributed to observed levels of genetic variability. It was expected that early colonists that could flower would contribute to subsequent recruiting cohorts, and that the limited number of such early reproductive colonists would lead to variance in mating success, inbreeding, or bottlenecks which could reduce genetic diversity and increase genetic differentiation among subsequent recruiting cohorts. Analyses of parentage (with paternity exclusion probability > 95%) for all recruiting plants demonstrated that in fact, there was little contribution by the early reproductive colonists to subsequent cohorts, and that immigration from outside the study sites in the form of seed dispersal accounted for over 94% of the recruitment in the study plots, with pollen dispersal accounting for less than 3% gene flow. No genetic bottleneck or evidence of reproductive skew in the recruiting cohorts were found, suggesting that propagule dispersal was from many source individuals in other established populations.
Mitochondrial DNA phylogeography of western lowland gorillas (Gorilla gorilla gorilla)
Authors: Clifford Stephen L. , Anthony Nicola M. , Bawe‐Johnson Mireille , Abernethy Kate A. , Tutin Caroline E. G. , White Lee J. T. , Bermejo Magdelena , Goldsmith Michelle L. , McFarland Kelley , Jeffery Kathryn J. , Bruford Michael W. , Wickings E. Jean
Published: May 2004

The geographical distribution of genetic variation within western lowland gorillas (Gorilla gorilla gorilla) was examined to clarify the population genetic structure and recent evolutionary history of this group. DNA was amplified from shed hair collected from sites across the range of the three traditionally recognized gorilla subspecies: western lowland (G. g. gorilla), eastern lowland (G. g. graueri) and mountain (G. g. beringei) gorillas. Nucleotide sequence variation was examined in the first hypervariable domain of the mitochondrial control region and was much higher in western lowland gorillas than in either of the other two subspecies. In addition to recapitulating the major evolutionary split between eastern and western lowland gorillas, phylogenetic analysis indicates a phylogeographical division within western lowland gorillas, one haplogroup comprising gorilla populations from eastern Nigeria through to southeast Cameroon and a second comprising all other western lowland gorillas. Within this second haplogroup, haplotypes appear to be partitioned geographically into three subgroups: (i) Equatorial Guinea, (ii) Central African Republic, and (iii) Gabon and adjacent Congo. There is also evidence of limited haplotype admixture in northeastern Gabon and southeast Cameroon. The phylogeographical patterns are broadly consistent with those predicted by current Pleistocene refuge hypotheses for the region and suggest that historical events have played an important role in shaping the population structure of this subspecies.
Tracing back seed and pollen flow within the crop–wild Beta vulgaris complex: genetic distinctiveness vs. hot spots of hybridization over a regional scale
Authors: Viard Frédérique , Arnaud Jean‐François , Delescluse Maxime , Cuguen Joël
Published: May 2004

Hybrids between transgenic crops and wild relatives have been documented successfully in a wide range of cultivated species, having implications on conservation and biosafety management. Nonetheless, the magnitude and frequency of hybridization in the wild is still an open question, in particular when considering several populations at the landscape level. The Beta vulgaris complex provides an excellent biological model to tackle this issue. Weed beets contaminating sugar beet fields are expected to act as a relay between wild populations and crops and from crops‐to‐crops. In one major European sugar beet production area, nine wild populations and 12 weed populations were genetically characterized using cytoplasmic markers specific to the cultivated lines and nuclear microsatellite loci. A tremendous overall genetic differentiation between neighbouring wild and weed populations was depicted. However, genetic admixture analyses at the individual level revealed clear evidence for gene flow between wild and weed populations. In particular, one wild population displayed a high magnitude of nuclear genetic admixture, reinforced by direct seed flow as evidenced by cytoplasmic markers. Altogether, weed beets were shown to act as relay for gene flow between crops to wild populations and crops to crops by pollen and seeds at a landscape level.
Genetic evidence reveals density‐dependent mediated success of alternative mating behaviours in the European bitterling (Rhodeus sericeus)
Authors: Reichard M. , Smith C. , Jordan W. C.
Published: May 2004

The reproductive success of alternative mating behaviours may vary within and among populations in relation to environmental factors and demographic parameters. We used behavioural and genetic data to investigate how male density affects reproductive success of territoriality and sneaking in the European bitterling (Rhodeus sericeus, Cyprinidae), a freshwater fish that spawns on the gills of living freshwater mussels. Keeping the number of spawning sites constant, we manipulated male densities in laboratory and mesocosm experiments. We showed that sneaked fertilizations were common in R. sericeus, and that they increased significantly with male density. Territorial mating was almost 17 times more successful than sneaking at the lowest male density treatment, and still 2–3 times more successful at intermediate densities. However, both behaviours conferred the same fitness pay‐off at the highest male density. While the success of territorial males declined with male density, the success of individual sneaking males remained constant across densities. Notably, the capacity of territorial males to outcompete sneakers by preoviposition sperm loading was the best predictor of male reproductive success, rather than aggression, body size or postoviposition ejaculation.
Accuracy, efficiency and robustness of four algorithms allowing full sibship reconstruction from DNA marker data
Authors: Butler K. , Field C. , Herbinger C. M. , Smith B. R.
Published: May 2004

In the problem of reconstructing full sib pedigrees from DNA marker data, three existing algorithms and one new algorithm are compared in terms of accuracy, efficiency and robustness using real and simulated data sets. An algorithm based on the exclusion principle and another based on a maximization of the Simpson index were very accurate at reconstructing data sets comprising a few large families but had problems with data sets with limited family structure, while a Markov Chain Monte Carlo (MCMC) algorithm based on the maximization of a partition score had the opposite behaviour. An MCMC algorithm based on maximizing the full joint likelihood performed best in small data sets comprising several medium‐sized families but did not work well under most other conditions. It appears that the likelihood surface may be rough and presents challenges for the MCMC algorithm to find the global maximum. This likelihood algorithm also exhibited problems in reconstructing large family groups, due possibly to limits in computational precision. The accuracy of each algorithm improved with an increasing amount of information in the data set, and was very high with eight loci with eight alleles each. All four algorithms were quite robust to deviation from an idealized uniform allelic distribution, to departures from idealized Mendelian inheritance in simulated data sets and to the presence of null alleles. In contrast, none of the algorithms were very robust to the probable presence of error/mutation in the data. Depending upon the type of mutation or errors and the algorithm used, between 70 and 98% of the affected individuals were classified improperly on average.
Polyandry and fitness in the western harvester ant,Pogonomyrmex occidentalis
Authors: Wiernasz Diane C. , Perroni Christina L. , Cole Blaine J.
Published: May 2004

Using four highly polymorphic microsatellite markers (12–28 alleles), we gentoyped workers from 63 colonies ofPogonomyrmex occidentalis. Colonies have a single, multiply mated queen, and an average number of 6.3 patrilines per colony. Colony growth was measured over an 8‐year period in the study population. Intracolonial relatedness and colony growth are correlated negatively, indicating a substantial fitness benefit to multiple mating.
Hybridization and asymmetric reproductive isolation between the closely related bryophyte taxa Polytrichum commune and P. uliginosum
Authors: Van Der Velde M. , Bijlsma R.
Published: May 2004

Based on genetic differentiation, the haploid dioecious bryophyte taxa Polytrichum commune and P. uliginosum have been inferred to be completely reproductively isolated. However, analysing diploid sporophytes from a sympatric population for three diagnostic microsatellite markers, we show here that reproductive isolation between these taxa is far more complex and highly asymmetric. Isolation between ♀‐P. commune×♂‐P. uliginosum seems to be complete and prezygotic (or early postzygotic) as no hybrid sporophytes were observed on P. commune females. In the other direction (♀‐P. uliginosum×♂‐P. commune) isolation was clearly postzygotic as high frequencies of hybrid sporophytes were found on P. uliginosum females. However, during maturation these sporophytes showed irregular development, indicating that hybrid sporophytes are unlikely to produce ripe spores. Mechanisms possibly underlying this asymmetric reproductive isolation pattern are discussed. Notwithstanding hybrid offspring being unlikely, the high frequency of hybrid sporophytes observed suggests that viable spores may be formed occasionally through such rare processes as chromosome nondisjunction, possibly giving rise to allodiploids. Allodiploids have been reported in Polytrichum (and other bryophyte genera). Studies such as the one presented here will therefore help to elucidate the evolutionary importance of interspecific hybridization and allodiploidization in bryophyte speciation.