Summary 1.Spatially explicit Bayesian clustering techniques offer a powerful tool for ecology and wildlife management, as genetic divisions can be correlated with landscape features. We used these methods to analyse the genetic structure of a population of European wild boar Sus scrofa with the aim of identifying effective barriers for disease management units. However, it has been suggested that the methods could produce biased results when faced with deviations from random mating not caused by genetic discontinuities, such as isolation by distance (IBD). 2. We analysed a data set consisting of 697 wild boar multilocus genotypes using spatially explicit ( baps, geneland ) and non-explicit ( structure ) Bayesian methods. We also simulated and analysed data sets characterized by different degrees of IBD, with and without genetic discontinuities. 3. When analysing the empirical data set, different programs did not converge on the same clustering solution and some clusters were difficult to explain biologically. Results from the simulated data showed that IBD, also present in the empirical data set, could cause the Bayesian methods to overestimate genetic structure. Simulated barriers were identified correctly, but the programs superimposed further clusters at higher IBD levels. 4. It was not possible to ascertain with confidence whether the clustering solutions offered by the various programs were an accurate reflection of population genetic structure in our empirical data set or were artefacts created by the underlying IBD pattern. 5. Synthesis and applications : We show that Bayesian clustering methods can overestimate genetic structure when analysing an individual-based data set characterized by isolation by distance. This bias could lead to the erroneous delimitation of management or conservation units. Investigators should be critical and suspicious of clusters that cannot be explained biologically. Data sets should be tested for isolation by distance and conclusions should not be based on the output from just one method.
1. The diet of wild boar Sus scrofa in Western Europe is reviewed, paying particular attention to the consumption of agricultural crops and the implications of this from the point of view of crop damage. Data were taken mainly from 11 studies that provide quantitative information about the consumption of different food types, but we also list all the foods reported as being eaten by wild boar in a total of 21 studies. 2. Vegetable foods occurred more frequently in the diet than animal foods, and also constituted the bulk of the food ingested. Overall, there were four major vegetable food categories: mast, roots, green plant matter and agricultural crops. Depending on the study area, wild boar always consumed at least one energy-rich plant food such as acorns, beechnuts, chestnuts, pine seeds, olives, cereal grains or other crops. The number and types of agricultural crops consumed varied between study areas but crops represent an important component of wild boar diet throughout its Western European range. Among animal foods, insects, earthworms, birds and mammals were eaten most consistently but the diet also included amphibians, reptiles, gastropods and myriapods. 3. Seasonal, interannual and regional differences in the diet, together with its striking overall breadth, indicate that wild boar are opportunistic omnivores whose diet, in any particular instance, is largely determined by the relative availability of different food types. Dependence on energy-rich plant material as a major component of the diet, coupled with large body size and a propensity to trample crops as well as consume them, means that wild boar cause significant agricultural damage.
In many European countries, the wild boar (Sus scrofa) is often associated with crop damage. In this study, we analyse data relating to 13,276 cases of wild boar damage to agricultural crops over a 10-year period in Luxembourg (an area of 2,586 km 2 in Western Europe). Results show that (1) damage is more severe in this area than in others; (2) damage to permanent grassland is far more frequent and more severe than damage to annual crops; (3) trichomatous crops such as barley are avoided; (4) damage is seasonally distributed according to type of crop; (5) damage is distributed spatially in a non-uniform manner; (6) damage intensity is significantly correlated with wild boar hunting bags, both over time and space. We suggest that wild boar management strategy should always take into account the issue of damage to agricultural crops. Our results imply that measures for preventing or reducing damage should be more targeted in time and space and that adjustments to cropping patterns should contribute towards a reduction of wild boar damage.
Molecular forensic methods are being increasingly used to help enforce wildlife conservation laws. Using multilocus genotyping, illegal translocation of an animal can be demonstrated by excluding all potential source populations as an individual's population of origin. Here, we illustrate how this approach can be applied to a large continuous population by defining the population genetic structure and excluding suspect animals from each identified cluster. We aimed to test the hypothesis that recreational hunters had illegally introduced a group of red deer into a hunting area in Luxembourg. Reference samples were collected over a large area in order to test the possibility that the suspect individuals might be recent immigrants. Due to isolation-by-distance relationships in the data set, inferring the number of genetic clusters using Bayesian methods was not straightforward. Biologically meaningful clusters were only obtained by simultaneously analysing spatial and genetic information using the program baps 4.1. We inferred the presence of three genetic clusters in the study region. Using partial Mantel tests, we detected barriers to gene flow other than distance, probably created by a combination of urban areas, motorways and a river valley used for viticulture. The four focal animals could be excluded with a high certainty from the three genetic subpopulations and it was therefore likely that they had been released illegally.
Summary 1.Size is a basic attribute of any population but it is often difficult to estimate, especially if the species under investigation is rare or cryptic. For example, there is currently no cheap and robust way of estimating the abundance of the European badger Meles meles , despite the species' role as an agricultural pest and carrier of bovine tuberculosis. 2. We tested the reliability and accuracy of estimating badger abundance by genotyping DNA extracted from remotely plucked hair. We assessed the accuracy of our methodology by estimating local abundance by direct observation. Hair samples were collected near five target setts using a baited barbed wire enclosure or (at one sett) barbed wire suspended over a clearly visible badger run. All the hairs found on a barb were included in the extraction. 3. Of the 113 samples collected over a 6-month period, 105 gave rise to amplifiable DNA and originated from single animals. Through comparison with reliable reference genotypes of captured badgers, we showed that amplifiable DNA, including extracts obtained from single guard hairs, produced accurate profiles in a single round of amplifications. 4. Direct observation of the target setts suggested that a minimum of 13 badgers was present in the study area. Analysis of the 105 usable samples provided a baseline estimate of 15 animals. 5. To test the practical use of hair trapping to estimate population size, hair samples were collected daily during a 3-week period. The 66 usable samples obtained originated from 14 of the 15 known badgers. Estimates of true abundance were generated using rarefaction analyses, the least biased of which produced an abundance estimate of 14·23, corresponding well with the number of genetic profiles obtained over the 6-month period. The results allowed comparisons of theoretical predictions and empirical data relating to rarefaction analyses. 6. Synthesis and applications. DNA extracted from remotely plucked badger hair could form the basis of a potentially cost-effective, reliable and widely applicable method of estimating badger abundance. Hair trapping may offer a feasible method of estimating population size in a range of species even when the species are rare or patchily distributed.
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