Trophic niches of four sympatric rainforest anurans from southern Nigeria: does resource partitioning play a role in structuring the community ?

Le partage des ressources est un mécanisme qui peut réduire l'intensité de la compétition interspécifique dans un cortège d'espèces syntopiques, morphologiquement et éco-éthologiquement semblables. La documentation du partage des ressources, entre quatre espèces d'Anoures sympatriques, a été recherchée par l'examen du régime alimentaire (par dissection stomacale) de spécimens obtenus auprès de fournisseurs de viande de brousse dans le sud-est du Nigéria. Pour l'ensemble des quatres espèces, nous avons trouvé au total 32 différents types de proies. Ptychadena oxyrhynchus en a consommé 28, contre 17 pour P. aequiplicata, 15 pour Bufo maculatus et 10 seulement pour Hoplobatrachus occipitalis. Pour les courbes cumulatives de diversité des trois premières espèces un plateau a été atteint, montrant que la composition des régimes pouvait être considérée comme correctement établie. Les proies communes, consommées par les quatre espèces d'Anoures, étaient des Formicoidea, des Coléoptères adultes, des Aranéides, des Isopodes, des Oligochètes et des Pulmonés. Les proies communes, consommées par trois des quatre amphibiens, étaient des Dermaptères, des Hémiptères, des Odonates adultes et des Orthoptères. Les largeurs de tête variaient significativement entre les espèces d'Anoures ; toutefois, les deux espèces de Ptychadena ne montraient pas de différence significative entre elles sur ce point Pour trois espèces, la largeur de tête était significativement corrélée au volume de proies dans l'estomac. Le partage des ressources (en termes de types de proies) a été trouvé particulièrement net entre deux espèces de Ptychadena étroitement apparentées. La divergence entre Ptychadena oxyrhynchus et P. aequiplicata apparut telle que des analyses multivariées ont placé chacune d'elles, du point de vue alimentaire, plus près de Hoplobatrachus occipitalis ou de Bufo maculatus que de son congénère. Une divergence si forte semblerait jouer un rôle majeur dans le maintien de la structure de ce peuplement mixte d'Anoures.Resource partitioning is a mechanism that can reduce the intensity of inter-specifie competition between morphologically and eco-ethologically similar, syntopic species . Evidence for resource partitioning, between four syntopic anuran species, was investigated by examining the diet (through stomach dissection) of frogs bought from bush meat traders in southeastern Nigeria . Considering the four species together, a total of 32 different prey types were found. Ptychadena oxyrhynchus consumed 28 of them, while P. aequiplicata consumed 17 , Bufo maculatus 15 and Hoplobatrachus occipitalis only 10. For the first three species, the cumulative-diversity curves indicated that a plateau phase was reached, i .e . that the prey composition could be considered reliably assessed. Common prey items, which were consumed by all four anuran species, were : Formicoidea, Coleoptera adults, Araneidae, Jsopoda, Oligochaeta, and Pulmonata. Common prey items, which were consumed by three of the four amphibians, were : Dermaptera, Hemiptera, Odonata adults, and Orthoptera. Head width varied significantly between species, but there was no statistical difference between the two Ptychadena species. Head width was significantly correlated with prey volume in the stomach in each of three species. Resource partitioning (in terms of prey types) was found to be particularly strong between two closely related species of Ptychadena. The divergence bewteen Ptychadena oxyrhynchus and P. aequiplicata was such that multivariate analyses placed each one of them closer in feeding ecology to either Hoplobatrachus occipitalis or Bufo maculatus, than to their congener. Such strong divergence is hypothesized to play a major role in maintaining the structure of this mixed anuran community

Haplotype affinities resolve a major component of goat (<i>Capra hircus</i>) MtDNA D-loop diversity and reveal specific features of the Sardinian stock

Goat mtDNA haplogroup A is a poorly resolved lineage absorbing most of the overall diversity and is found in locations as distant as Eastern Asia and Southern Africa. Its phylogenetic dissection would cast light on an important portion of the spread of goat breeding. The aims of this work were 1) to provide an operational definition of meaningful mtDNA units within haplogroup A, 2) to investigate the mechanisms underlying the maintenance of diversity by considering the modes of selection operated by breeders and 3) to identify the peculiarities of Sardinian mtDNA types. We sequenced the mtDNA D-loop in a large sample of animals (1,591) which represents a non-trivial quota of the entire goat population of Sardinia. We found that Sardinia mirrors a large quota of mtDNA diversity of Western Eurasia in the number of variable sites, their mutational pattern and allele frequency. By using Bayesian analysis, a distance-based tree and a network analysis, we recognized demographically coherent groups of sequences identified by particular subsets of the variable positions. The results showed that this assignment system could be reproduced in other studies, capturing the greatest part of haplotype diversity. We identified haplotype groups overrepresented in Sardinian goats as a result of founder effects. We found that breeders maintain diversity of matrilines most likely through equalization of the reproductive potential. Moreover, the relevant amount of inter-farm mtDNA diversity found does not increase proportionally with distance. Our results illustrate the effects of breeding practices on the composition of maternal gene pool and identify mtDNA types that may be considered in projects aimed at retrieving the maternal component of the oldest breeds of Sardinia.</br

Haplotype Affinities Resolve a Major Component of Goat (Capra hircus) MtDNA D-Loop Diversity and Reveal Specific Features of the Sardinian Stock

Goat mtDNA haplogroup A is a poorly resolved lineage absorbing most of the overall diversity and is found in locations as distant as Eastern Asia and Southern Africa. Its phylogenetic dissection would cast light on an important portion of the spread of goat breeding. The aims of this work were 1) to provide an operational definition of meaningful mtDNA units within haplogroup A, 2) to investigate the mechanisms underlying the maintenance of diversity by considering the modes of selection operated by breeders and 3) to identify the peculiarities of Sardinian mtDNA types. We sequenced the mtDNA D-loop in a large sample of animals (1,591) which represents a non-trivial quota of the entire goat population of Sardinia. We found that Sardinia mirrors a large quota of mtDNA diversity of Western Eurasia in the number of variable sites, their mutational pattern and allele frequency. By using Bayesian analysis, a distance-based tree and a network analysis, we recognized demographically coherent groups of sequences identified by particular subsets of the variable positions. The results showed that this assignment system could be reproduced in other studies, capturing the greatest part of haplotype diversity

A population-based study of an Italian genetic isolate reveals that mean platelet volume is not a risk factor for thrombosis.

INTRODUCTION: Several studies revealed that mean platelet volume (MPV) was larger in the acute phase of arterial and venous thrombosis and predicted a poor clinical outcome. It has been suggested that MPV is a risk factor for thrombosis. However, it is unclear whether increased platelet size is a cause or a consequence of thrombosis. It was the objective of this study to verify whether MPV is a risk factor for arterial and venous thrombosis. METHODS: We search for associations between platelet parameters and thrombosis by a population-based study in 11,084 inhabitants of an Italian genetic isolate characterized by wide variability of platelet parameters. To validate this methodology of investigation, we also evaluated whether it was able to identify several well known thrombotic risk factors in the study population. RESULTS: Statistical analysis confirmed that male gender, ageing, hypertension, high total cholesterol, low HDL cholesterol, diabetes, obesity and smoking were risk factors for arterial thrombosis, while alcohol consumption had a protective effect. Female gender, ageing, pregnancy, estroprogestinic treatment, obesity, varicose veins were associated with venous thrombosis. At variance, MPV and platelet count were unrelated to previous thrombotic events. However, MPV was negatively correlated with the time since the last thrombotic event. CONCLUSIONS: This study indicated that an epidemiologic study of a population isolate is appropriate for the identification of thrombotic risk factors, but it failed to identify such a role for MPV. Thus, we suggest that the increased MPV previously described in subjects with acute thrombosis was a consequence instead of a cause of thrombosis

Analysis of 12,517 inhabitants of a Sardinian geographic isolate reveals that predispositions to thrombocytopenia and thrombocytosis are inherited traits

Background Thrombocytopenia is a common finding in several diseases but almost nothing is known about the prevalence of thrombocytopenia in the general population. We examined the prevalence of thrombocytopenia and determinants of platelet count in a healthy population with a wide age range. Design and Methods We performed a cross-sectional study on 12,517 inhabitants of ten villages (80% of residents) in a secluded area of Sardinia (Ogliastra). Participants underwent a complete blood count evaluation and a structured questionnaire, used to collect epidemiological data. Results We observed a platelet count lower than 150¥109/L in 3.2% (2.8%-3.6%) of females and 4.8% (4.3%-5.4%) of males, with a value of 3.9% (3.6%-4.3%) in the entire population. Thrombocytopenia was mild (platelet count: 100¥109/L -150¥109/L), asymptomatic and not associated with other cytopenias or overt disorders in most cases. Its standardized prevalence was quite different in different villages, with values ranging from 1.5% to 6.8%, and was negatively correlated with the prevalence of a mild form of thrombocytosis, which ranged from 0.9% to 4.5%. Analysis of platelet counts across classes of age revealed that platelet number decreased progressively with aging. As a consequence, thrombocytopenia was nearly absent in young people and its prevalence increased regularly during lifetime. The opposite occurred for thrombocytosis. Conclusions Given the high genetic differentiation among Ogliastra villages with “high” and “low” platelet counts and the substantial heritability of this quantitative trait (54%), we concluded that the propensity to present mild and transient thrombocytosis in youth and to acquire mild thrombocytopenia during aging are new genetic traits

A Genomewide Search Using an Original Pairwise Sampling Approach for Large Genealogies Identifies a New Locus for Total and Low-Density Lipoprotein Cholesterol in Two Genetically Differentiated Isolates of Sardinia

A powerful approach to mapping the genes for complex traits is to study isolated founder populations, in which genetic heterogeneity and environmental noise are likely to be reduced and in which extended genealogical data are often available. Using graph theory, we applied an approach that involved sampling from the large number of pairwise relationships present in an extended genealogy to reconstruct sets of subpedigrees that maximize the useful information for linkage mapping while minimizing calculation burden. We investigated, through simulation, the properties of the different sets in terms of bias in identity-by-descent (IBD) estimation and power decrease under various genetic models. We applied this approach to a small isolated population from Sardinia, the village of Talana, consisting of a unique large and complex pedigree, and performed a genomewide search through variance-components linkage analysis for serum lipid levels. We identified a region of significant linkage on chromosome 2 for total serum cholesterol and low-density lipoprotein (LDL) cholesterol. Through higher-density mapping, we obtained an increased linkage for both traits on 2q21.2-q24.1, with a LOD score of 4.3 for total serum cholesterol and of 3.9 for LDL cholesterol. A replication study was performed in an independent and larger set from a genetically differentiated isolated population of the same region of Sardinia, the village of Perdasdefogu. We obtained consistent linkage to the region for total serum cholesterol (LOD score 1.4) and LDL cholesterol (LOD score 2.2), with a level of concordance uncommon for complex traits, and refined the location of the quantitative-trait locus. Interestingly, the 2q21.1-22 region has also been linked to premature coronary heart disease in Finns, and, in the adjacent 2q14 region, significant linkage with triglycerides has been reported in Hutterites

Dissecting metabolic syndrome components: data from an epidemiologic survey in a genetic isolate.

The metabolic syndrome (MetS) is a large-scale and expanding public-health and clinical threat worldwide. We investigated the determinants of MetS, assessed its prevalence and components and, estimated their genetic contribution, taking advantage of the special characteristics of Sardinian isolated populations. Inhabitants of 10 villages in Ogliastra region participated in a cross-sectional survey in 2002-2008 (n = 9,647). Blood samples, blood pressure (BP), anthropometry and, data from a standardized interview were collected. Prevalence of MetS was estimated by the direct method of standardization. Variables associated with the MetS were identified using multilevel logistic regression. Heritability was determined using variance component models. MetS Prevalence was 19.6% (95% CI 18.9-20.4%) according to NCEP-ATPIII, 24.8% (95% CI 24.0-25.6%) according to IDF and, 29% (95% CI 28.1-29.8%) according to AHA/NHLBI harmonized criteria, ranging from 9 to 26% among villages. The most prevalent combination was BP + HDL-cholesterol (HDL) + triglycerides (TRIG) (19%), followed by BP + HDL + waist circumference (WAIST) (17%) and, BP + HDL + TRIG + WAIST (13.6%). Heritability of MetS was 48% (p = 1.62 × 10(-25)), as the two most common combinations (BP + HDL + TRIG and BP + HDL + WAIST) showed heritability of 53 and 52%, respectively. The larger genetic components of the two most frequent combinations determining MetS deserve greater investigation in order to understand the underlying mechanisms. Besides, further studies are warranted to confirm these findings both in isolated and outbred populations

History, geography and population structure influence the distribution and heritability of blood and anthropometric quantitative traits in nine Sardinian genetic isolates

Isolated founder populations which exhibit great genetic and environmental homogeneity provide an attractive setting for the study of quantitative traits (QTs). Geneticists have repeatedly turned to population isolates and the past successes have prompted increased interest among medical researchers. We studied nine small isolated villages of a secluded area of Sardinia (Ogliastra), all of them characterized by a few founders, high endogamy rates, slow population expansion and a distinct genetic makeup. Anthropometric and blood parameters, 43 QTs in all, were analysed in about 9000 voluntary subjects for whom extended genealogical information was available. We explored the distribution and examined mean differences of each trait among villages by analysis of variance (ANOVA). A heritability analysis with the variance component (VC) method was performed. Results show significant differences in the distribution of most traits between groups of villages located in two distinct geographical areas already identified by a previous population structure analysis, thus supporting the existence of differentiation among sub-populations in the same region. Heritability estimates range between 30 and 89%, demonstrating that genetic effects substantially contribute to phenotypic variation of all investigated traits and that this population provides excellent research conditions for gene-mapping projects. Results suggest that history, geographic location and population structure may have influenced the genetic and phenotypic features of these isolates. Our findings may be useful for the ongoing linkage and association studies in these isolates and suggest that a thorough characterization of population is valuable to better identify genes or variants that may be rare in the population at large and peculiar to single villages

Median joining network of 30 sequences showing the occurrence of 23 non-synonymous substitutions.

<p>Each circle represents a sequence. Branch length is proportional to the number of mutations. Note that two A11 and two uncharacterized sequences are lumped into single (larger) nodes (see Materials and Methods). The haplogroup or D-loop clade (for Hg A) affiliation of clusters of sequences is shown in large empty characters. Aminoacid replacements are shown beside each branch in their polarized form. The Hg A portion of the network is magnified while the original network is in the inset. A large lozenge indicates the likely position of the root and was added in the drawing to partition three variants peculiar of Hg C. Their polarization was obtained by comparison with <i>C. ibex</i>.</p