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Evolutionary genetics of MHC class II beta genes in the brown hare, Lepus europaeus.

ABSTRACT: The genes of the major histocompatibility complex (MHC) are attractive candidates for investigating the link between adaptive variation and individual fitness. High levels of diversity at the MHC are thought to be the result of parasite-mediated selection and there is growing evidence to support this theory. Most studies, however, target just a single gene within the MHC and infer any evidence of selection to be representative of the entire gene region. Here we present data from three MHC class II beta genes (DPB, DQB, and DRB) for brown hares in two geographic regions and compare them against previous results from a class II alpha-chain gene (DQA). We report moderate levels of diversity and high levels of population differentiation in the DQB and DRB genes (Na ?=? 11, D (est)?=? 0.071 and Na ?= 15, D (est)?=? 0.409, respectively), but not for the DPB gene (Na ?=? 4, D (est)?=? 0.00). We also detected evidence of positive selection within the peptide binding region of the DQB and DRB genes (95% CI, ? ?>? 1.0) but found no signature of selection for DPB. Mutation and recombination were both found to be important processes shaping the evolution of the class II genes. Our findings suggest that while diversifying selection is a significant contributor to the generally high levels of MHC diversity, it does not act in a uniform manner across the entire MHC class II region. The beta-chain genes that we have characterized provide a valuable set of MHC class II markers for future studies of the evolution of adaptive variation in Leporids.

SUBMITTER: Smith S

PROVIDER: S-EPMC3190090 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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Evolutionary genetics of MHC class II beta genes in the brown hare, Lepus europaeus.

Smith Steve S de Bellocq Joëlle Goüy JG Suchentrunk Franz F Schaschl Helmut H

Immunogenetics 20110618 11

The genes of the major histocompatibility complex (MHC) are attractive candidates for investigating the link between adaptive variation and individual fitness. High levels of diversity at the MHC are thought to be the result of parasite-mediated selection and there is growing evidence to support this theory. Most studies, however, target just a single gene within the MHC and infer any evidence of selection to be representative of the entire gene region. Here we present data from three MHC class ...[more]

PMID: 21688061

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Project description:In Northern Italy, a hastening of hare population decline was noticeable from 2008. In the same year hunters reported a sudden increase of hares infected by Taenia sp. larvae, whose morphology was consistent with T. pisiformis cysticerci. The aim of the survey was: i)to identify the parasites through morphological features and molecular techniques; ii)to quantify the prevalence and abundance of cysticerci in hunted hares; iii)to describe pathological aspects of parasite-induced lesions; iv)to evaluate the short-term trend of the infection comparing two different hunting seasons; v)to highlight possible relationship between T. pisiformis infection and hare-related variables. In 2013, 2015 the viscera of 54 and 61 hares legally hunted in agro-ecosystems of the Po Plain were collected. Peritoneum, liver and lungs were examined for cysticercosis; abundance was estimated counting superficial parasites in liver; parasites were microscopically identified by shape and measure of both large and small hooks. One cysticercus from each hare was analized by a PCR targeting Taeniid species and then sequenced. Frozen liver, lungs and gastrointestinal peritoneum were macroscopically observed and, after thawing, representative samples from the available organs were collected for histologic examination to verify parasitic cysts and the subsequent damage of the involved organs. Sex, weight and age class of the animals were recorded. Generalized linear models were used for statistical analysis. T. pisiformis was isolated in 8 hares in 2013 (prevalence 14.8%; abundance range: 0-400; mean abundance 17.8) and in 2 hares in 2015 (prevalence 3.28%; abundance range: 0-180; mean abundance 3.22). Identification was confirmed morphologically and by PCR. The DNA sequencing confirmed T. pisiformis in all samples. The sequences were all identical each-other. Infection was significantly related with adult age class, sampling year and low full-weight. Epidemiological and pathological pattern suggest both a possible role on host population health and a tendency toward host-parasite equilibrium.

Project description:In female mammals, reproduction, and in particular lactation, is the energetically most exigent life-history phase. Reproduction is strongly controlled by body reserves and food availability, so females with better body condition or food supply are believed to have higher reproductive output. Additionally, the growth and mortality of young mammals depends on their postnatal development. Therefore, the degree of precociality affects energetic demands for both mothers and young. To study the reproductive performance of the precocial European hare (Lepus europaeus), we analysed relationships between six predictor variables describing maternal and environmental effects and nine response variables relating to reproduction from 217 captive females. We compared the data with those of precocial and altricial mammal species from an extensive literature search. For hares, we found: (1) Heavier females had heavier litters at birth. (2) In summer and spring, total litter mass was larger than in winter. (3) At the end of lactation, the litters of multiparous females were heavier than those of primiparous females. (4) Both older females and females giving birth for the first time had relatively high leveret mortality during lactation. Comparing our results with the literature for other mammals revealed that the body condition (i.e., body mass) of females before birth is predictive of reproductive parameters in both precocial and altricial species. In the precocial hare, female body condition is no longer predictive of reproductive parameters at the end of lactation, whereas in altricial species, female body condition remains predictive of reproduction (litter mass at the end of lactation, offspring mortality) until the end of lactation. We conclude that these effects are caused by precocial offspring feeding on solid food soon after birth and, thus, being less dependent on the mother's body condition during lactation than altricial offspring. In line with this, precociality might have evolved as a way of buffering offspring against maternal effects.

Project description:BackgroundThe European brown hare (Lepus europaeus) typically resides in open habitats in agriculturally dominated landscapes in Europe. Over recent decades, a widely observed population decline occurred, which was attributed to agricultural intensification. However, with political incentives for specific crops, especially maize for energy production, the habitat went through massive changes. Thus, there is the need to identify parameters that characterize a suitable habitat for the brown hare in today's agricultural lands.ResultsWe modelled European brown hare densities spatially and temporally explicit over 10 years (2005-2014) across an entire federal state. The generalized additive mixed model confirms a constant decline of the European brown hare population in Lower Saxony. Municipalities with a high proportion of grassland and precipitation totaling up to 900 mm are more favored. Woodland showed an approximately linear negative effect. The most important agricultural crop groups such as winter grains and winter oilseed rape showed overall positive effects on hare densities. However, the effect of maize was unimodal, with a positive effect of medium proportions, but a negative effect of very high proportions. The effect of sugar beet was relatively weak but negative. Brown hares were also more abundant in municipalities with a higher density of vixen with litter and municipalities with a high proportion of wildflower strips showed higher brown hare abundance.ConclusionLower Saxony is a diverse federal state with grassland dominated areas in the northwest, more woodland in the east, but intensive arable land in most remaining areas. The European brown hare-a species with a wide ecological potency-shows preferences to both grassland and the most typical arable crop groups such as winter grains and winter oilseed rape. The substantial increase in maize production within the time frame was likely unfavourable and may be one reason for the decline. Nonetheless, political tools such as the agri-environmental scheme "wildflower strips" were beneficial for the brown hare abundance and may be an option to reverse the decline seen over the 10 years.

Dataset Information

Evolutionary genetics of MHC class II beta genes in the brown hare, Lepus europaeus.

Publications

Evolutionary genetics of MHC class II beta genes in the brown hare, Lepus europaeus.

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