Uma pitada de tempero da vida: variação também é boa para as lebres

sexta-feira, novembro 26, 2010

Spice of Life: Variety Is Also Good for Hares

ScienceDaily (Nov. 25, 2010) — Since 1871, when Charles Darwin wrote The Descent of Man, it has been widely accepted that "Variability is the necessary basis for the action of selection." Variability is associated with the ability to adapt, which is clearly beneficial at a species level. But there is increasing evidence that genetic variability may also give rise to advantages at the level of the individual. Steve Smith and Franz Suchentrunk at the Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna have now shown that variation at a particular gene locus in hares is associated with greater reproductive success.

Young hare. (Credit: Vetmeduni Vienna/Teresa Valencak)

The results are published in the October issue of the journal Molecular Ecology.

One of the key questions of evolutionary biology is how variation at the level of single genes affects animals' ability to produce young. Together with collaborators in the UK and in Belgium, Steve Smith and Franz Suchentrunk at the Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna have designed a mathematical model to describe the effects of genetic variation on the reproductive success of the European hare. They tested the model on data obtained from wild hares in Belgium and in eastern Austria.

Smith and colleagues elected to examine the influence of two different sites in the major histocompatability complex (MHC). The MHC is involved in immune reactions and MHC genes have recently received a great deal of attention as representing a possible link between genetic variation and fitness. A number of studies have implicated them as possible causes of reproductive failure in humans but to date no experiments have attempted to assess whether MHC genes are associated with fitness in populations of wild animals.

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Molecular Ecology
Volume 19, Issue 19, pages 4131–4143, October 2010

Homozygosity at a class II MHC locus depresses female reproductive ability in European brown hares


Article first published online: 20 AUG 2010

DOI: 10.1111/j.1365-294X.2010.04765.x

Keywords: Bayesian analysis; DQA; DRB; Lepus europaeus; MHC variation; reproductive success; zero-inflated Poisson regression model 


The link between adaptive genetic variation, individual fitness and wildlife population dynamics is fundamental to the study of ecology and evolutionary biology. In this study, a Bayesian modelling approach was employed to examine whether individual variability at two major histocompatibility complex (MHC) class II loci (DQA and DRB) and eight neutral microsatellite loci explained variation in female reproductive success for wild populations of European brown hare (Lepus europaeus). We examined two aspects of reproduction: the ability to reproduce (sterility) and the number of offspring produced (fecundity). Samples were collected from eastern Austria, experiencing a sub-continental climatic regime, and from Belgium with a more Atlantic-influenced climate. As expected, reproductive success (both sterility and fecundity) was significantly influenced by age regardless of sampling locality. For Belgium, there was also a significant effect of DQA heterozygosity in determining whether females were able to reproduce (95% highest posterior density interval of the regression parameter [−3.64, −0.52]), but no corresponding effect was found for Austria. In neither region was reproduction significantly associated with heterozygosity at the DRB locus. DQA heterozygotes from both regions also showed a clear tendency, but not significantly so, to produce a larger number of offspring. Predictive simulations showed that, in Belgium, sub-populations of homozygotes will have higher rates of sterile individuals and lower average offspring numbers than heterozygotes. No similar effect is predicted for Austria. The mechanism for the spatial MHC effect is likely to be connected to mate choice for increased heterozygosity or to the linkage of certain MHC alleles with lethal recessives at other loci.


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