Mixed ancestry from wild and domestic lineages contributes to the rapid expansion of invasive feral swine

Invasive alien species are a significant threat to both economic and ecological systems. Identifying the processes that give rise to invasive populations is essential for implementing effective control strategies. We conducted an ancestry analysis of invasive feral swine (Sus scrofa, Linnaeus, 1758), a highly destructive ungulate that is widely distributed throughout the contiguous United States, to describe introduction pathways, sources of newly emergent populations and processes contributing to an ongoing invasion. Comparisons of high‐density single nucleotide polymorphism genotypes for 6,566 invasive feral swine to a comprehensive reference set of S. scrofa revealed that the vast majority of feral swine were of mixed ancestry, with dominant genetic associations to Western heritage breeds of domestic pig and European populations of wild boar. Further, the rapid expansion of invasive feral swine over the past 30 years was attributable to secondary introductions from established populations of admixed ancestry as opposed to direct introductions of domestic breeds or wild boar. Spatially widespread genetic associations of invasive feral swine to European wild boar deviated strongly from historical S. scrofa introduction pressure, which was largely restricted to domestic pigs with infrequent, localized wild boar releases. The deviation between historical introduction pressure and contemporary genetic ancestry suggests wild boar‐hybridization may contribute to differential fitness in the environment and heightened invasive potential for individuals of admixed domestic pig–wild boar ancestry.     

Towards understanding wild boar Sus scrofa movement: a synthetic movement ecology approach

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Genetic evidence for introgression between domestic pigs and wild boars (Sus scrofa) in Belgium and Luxembourg: a comparative approach with multiple marker systems

Hybridization between wild species and their domestic relatives can be an important conservation and management problem. Genetic purity of the wild species is desirable per se and the phenomenon can have unpredictable evolutionary consequences. Declining European wild boar populations were frequently restocked with farmed wild boars that sometimes had been crossed with domestic pigs. We used simple polymerase chain reaction‐based diagnostic tests to detect the presence of mitochondrial DNA and coat colour alleles of domestic origin in wild boars from Belgium, Luxembourg, and western Germany. Microsatellite genotypes were used to test for genetic admixture between the wild boars and domestic pigs. Although almost one‐third of all Luxembourg wild boars carried Asian mitochondrial DNA haplotypes originating from domestic pigs, microsatellite‐based clustering only identified four putatively admixed individuals in Luxembourg. By contrast, clustering identified wild boar × domestic hybrids in most sampling locations in Belgium. We interpret these results as evidence of releases of hybrid captive‐reared wild boars. Our results emphasize the need (if working with classical markers) to use different systems to obtain an understanding as to whether hybridization between wild and domestic relatives might have affected the genetic make‐up of a local population. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 104–115.     

Novel Y‐chromosome short tandem repeats in Sus scrofa and their variation in European wild boar and domestic pig populations

Y‐chromosome markers are important tools for studying male‐specific gene flow within and between populations, hybridization patterns and kinship. However, their use in non‐human mammals is often hampered by the lack of Y‐specific polymorphic markers. We identified new male‐specific short tandem repeats (STRs) in Sus scrofa using the available genome sequence. We selected four polymorphic loci (5–10 alleles per locus), falling in one duplicated and two single‐copy regions. A total of 32 haplotypes were found by screening 211 individuals from eight wild boar populations across Europe and five domestic pig populations. European wild boar were characterized by significantly higher levels of haplotype diversity compared to European domestic pigs (H_D = 0.904 ± 0.011 and H_D = 0.491 ± 0.077 respectively). Relationships among STR haplotypes were investigated by combining them with single nucleotide polymorphisms at two linked genes (AMELY and UTY) in a network analysis. A differentiation between wild and domestic populations was observed (F_ST = 0.229), with commercial breeds sharing no Y haplotype with the sampled wild boar. Similarly, a certain degree of geographic differentiation was observed across Europe, with a number of local private haplotypes and high diversity in northern populations. The described Y‐chromosome markers can be useful to track male inheritance and gene flow in wild and domestic populations, promising to provide insights into evolutionary and population genetics in Sus scrofa.     

The Balkans and the colonization of Europe: the post‐glacial range expansion of the wild boar,Sus scrofa

Aim We focus on the biogeographical role of the Balkan Peninsula as a glacial refugium and source of northward post‐glacial dispersal for many European taxa. Specifically, we analysed the genetic structure and variation of wild boar (Sus scrofa) samples primarily from Greece, a region that has repeatedly served as a glacial refugium within the Balkan Peninsula. Location Continental Greece, the Aegean island of Samos and Bulgaria. Methods We analysed wild boar samples from 18 localities. Samples from common domestic breeds were also examined to take into account interactions between wild and domesticated animals. Phylogenetic analyses were carried out on a 637‐bp fragment of the mitochondrial DNA control region in 200 wild boar and 27 domestic pigs. The sequences were also compared with 791 Eurasian wild boar and domestic pig D‐loop sequences obtained from GenBank. Results Ninety‐four haplotypes were identified in the European wild boar data set, of which 68 were found in the Balkan samples and assigned to two previously described clades: the E1 European and Near Eastern clades. All of the continental samples clustered in the E1 clade and the samples from Samos fell into the Near Eastern clade, consistent with the island’s proximity to Asia Minor. Intriguingly, 62 novel haplotypes were identified and are found exclusively in the Balkans. Only six haplotypes were shared between wild boar and domestic pigs. Main conclusions Our data reveal numerous novel and geographically restricted haplotypes in wild boar populations, suggesting the presence of separate refugia in the Balkans. Our analyses support the hypothesis of a post‐glacial wild boar expansion consistent with the leading edge model, north and west from modern day Greece, and suggest little maternal introgression of Near Eastern and domestic haplotypes into wild Balkan populations.     

Ancient vs. recent processes as factors shaping the genetic variation of the European wild boar: are the effects of the last glaciation still detectable?

The European wild boar is an important game species, subjected to local extinctions and translocations in the past, and currently enormously and worryingly expanding in some areas where management is urgently required. Understanding the relative roles of ancient and recent events in shaping the genetic structure of this species is therefore not only an interesting scientific issue, but it represents also the basis for addressing future management strategies. In addition, several pig breeds descend from the European wild boar, but the geographical location of the domestication area(s) and the possible introgression of pig genomes into wild populations are still open questions. Here, we analysed the genetic variation in different wild boar populations in Europe. Ten polymorphic microsatellites were typed in 252 wild boars and the mtDNA control region was sequenced in a subset of 145 individuals. Some samples from different pig breeds were also analysed. Our results, which were obtained considering also 612 published mtDNA sequences, suggest that (i) most populations are similarly differentiated, but the major discontinuity is found along the Alps; (ii) except for the Italian populations, European wild boars show the signature of a postglacial demographic expansion; (iii) Italian populations seem to preserve a high proportion of preglaciation diversity; (iv) the demographic decline which occurred in some areas in the last few centuries did not produce a noticeable reduction of genetic variation; (v) signs of human-mediated gene flow among populations are weak, although in some regions the effects of translocations are detectable and a low degree of pig introgression can be identified; (vi) the hypothesis of an independent domestication centre in Italy is not supported by our data, which in turn confirm that Central European wild boar might have represented an important source for domestic breeds. We can therefore conclude that recent human activities had a limited effect on the wild boar genetic structure. It follows that areas with high variation and differentiation represent natural reservoirs of genetic diversity to be protected avoiding translocations. In this context controlling some populations by hunting is not expected to affect significantly genetic variation in this species.     

Environmental gradients shape the genetic structure of two medicinal Salvia species in Jordan

• Environmental gradients, and particularly climatic variables, exert a strong influence on plant distribution and, potentially, population genetic diversity and differentiation. Differences in water availability can cause among‐population variation in ecological processes and can thus interrupt populations’ connectivity and isolate them environmentally. The present study examines the effect of environmental heterogeneity on plant populations due to environmental isolation unrelated to geographic distance.
• Using AFLP markers, we analyzed genetic diversity and differentiation among 12 Salvia spinosa populations and 13 Salvia syriaca populations from three phytogeographical regions (Mediterranean, Irano‐Turanian and Saharo‐Arabian) representing the extent of the species’ geographic range in Jordan. Differences in geographic location and climate were considered in the analyses.
• For both species, flowering phenology varied among populations and regions. Irano‐Turanian and Saharo‐Arabian populations had higher genetic diversity than Mediterranean populations, and genetic diversity increased significantly with increasing temperature. Genetic diversity in Salvia syriaca was affected by population size, while genetic diversity responded to drought in S. spinosa. For both species, high levels of genetic differentiation were found as well as two well‐supported phytogeographical groups of populations, with Mediterranean populations clustering in one group and the Irano‐Turanian and Saharo‐Arabian populations in another. Genetic distance was significantly correlated to environmental distance, but not to geographic distance.
• Our data indicate that populations from moist vs. arid environments are environmentally isolated, where environmental gradients affect their flowering phenology, limit gene flow and shape their genetic structure. We conclude that environmental heterogeneity may act as driver for the observed variation in genetic diversity.

     

Genetic structure of the Canarian palm tree (Phoenix canariensis) at the island scale: does the ‘island within islands’ concept apply to species with high colonisation ability?

• Oceanic islands are dynamic settings that often promote within‐island patterns of strong population differentiation. Species with high colonisation abilities, however, are less likely to be affected by genetic barriers, but island size may impact on species genetic structure regardless of dispersal ability.
• The aim of the present study was to identify the patterns and factors responsible for the structure of genetic diversity at the island scale in Phoenix canariensis, a palm species with high dispersal potential. To this end, we conducted extensive population sampling on the three Canary Islands where the species is more abundant and assessed patterns of genetic variation at eight microsatellite loci, considering different within‐island scales.
• Our analyses revealed significant genetic structure on each of the three islands analysed, but the patterns and level of structure differed greatly among islands. Thus, genetic differentiation fitted an isolation‐by‐distance pattern on islands with high population densities (La Gomera and Gran Canaria), but such a pattern was not found on Tenerife due to strong isolation between colonised areas. In addition, we found a positive correlation between population geographic isolation and fine‐scale genetic structure.
• This study highlights that island size is not necessarily a factor causing strong population differentiation on large islands, whereas high colonisation ability does not always promote genetic connectivity among neighbouring populations. The spatial distribution of populations (i.e. landscape occupancy) can thus be a more important driver of plant genetic structure than other island, or species′ life‐history attributes.

     

Population genomics of wild and laboratory zebrafish (Danio rerio)

Understanding a wider range of genotype–phenotype associations can be achieved through ecological and evolutionary studies of traditional laboratory models. Here, we conducted the first large‐scale geographic analysis of genetic variation within and among wild zebrafish (Danio rerio) populations occurring in Nepal, India, and Bangladesh, and we genetically compared wild populations to several commonly used lab strains. We examined genetic variation at 1832 polymorphic EST‐based single nucleotide polymorphisms (SNPs) and the cytb mitochondrial gene in 13 wild populations and three lab strains. Natural populations were subdivided into three major mitochondrial DNA clades with an average among‐clade sequence divergence of 5.8%. SNPs revealed five major evolutionarily and genetically distinct groups with an overall F_ST of 0.170 (95% CI 0.105–0.254). These genetic groups corresponded to discrete geographic regions and appear to reflect isolation in refugia during past climate cycles. We detected 71 significantly divergent outlier loci (3.4%) and nine loci (0.5%) with significantly low F_ST values. Valleys of reduced heterozygosity, consistent with selective sweeps, surrounded six of the 71 outliers (8.5%). The lab strains formed two additional groups that were genetically distinct from all wild populations. An additional subset of outlier loci was consistent with domestication selection within lab strains. Substantial genetic variation that exists in zebrafish as a whole is missing from lab strains that we analysed. A combination of laboratory and field studies that incorporates genetic variation from divergent wild populations along with the wealth of molecular information available for this model organism provides an opportunity to advance our understanding of genetic influences on phenotypic variation for a vertebrate species.     

Potential ecological and epidemiological factors affecting the persistence of classical swine fever in wild boar Sus scrofa populations

• 1 Classical swine fever has increased in economic importance since it has become endemic in some wild boar Sus scrofa populations in Europe. The mechanism of disease persistence is still not well understood, and several aspects of both the ecology of boar and the virus are claimed to be responsible for disease persistence.
• 2 We review literature on the spread and persistence of the disease in free‐ranging wild boar. We determine whether the available knowledge can explain the observed patterns via mechanistic processes and their interactions, and assemble knowledge in a conceptual model.
• 3 We speculate that the most important factor explaining disease persistence is an alteration in disease outcome, resulting in individual courses with prolonged infectiousness or a sustained reproductive population through immunity. This effect is reinforced by high wild boar numbers either within sites or scattered over larger areas.
• 4 We highlight the sparse knowledge of disease transmission between wild boar. We derive management suggestions for different phases of an outbreak based on the conceptual model and advocate the use of model‐based investigations to test alternative management options.

     

The status of tuberculosis in European wild mammals

• 1 Tuberculosis (TB) is a chronic disease caused by Mycobacterium bovis and related members of the Mycobacterium tuberculosis complex. Infection affects not only cattle but also other livestock species, companion animals and wild mammals. Humans are also susceptible; hence, zoonotic infection is a driver for disease control in animal hosts. As bovine TB prevalence has been reduced in livestock, the relative epidemiological and socio‐economic importance of wildlife reservoirs has increased, and there is a need for disease management strategies.
• 2 We review the current status of TB in European wild mammals, identifying epidemiological trends and areas for future research and management. TB has a complex epidemiology, which may involve multiple hosts, and is influenced by climate and habitat.
• 3 Consequently, the role of wild and domestic hosts in the epidemiology of TB varies among regions. In Europe, there are three regional examples of M. bovis maintenance hosts: the Eurasian badger Meles meles in Great Britain and Ireland, the Eurasian wild boar Sus scrofa in the Iberian Peninsula and deer belonging to the subfamily Cervinae in several European regions. In other parts of Europe, these species are currently regarded as spillover hosts, although in time their status may change depending on local or regional risk factors. Nevertheless, in most situations, the relative contribution of wild mammals to M. bovis infection in cattle is still a matter of debate. Also, the outcome of management interventions to control disease in wildlife populations may be complex and counter‐intuitive.
• 4 As our knowledge of disease dynamics in wild mammals improves, options for disease control in wildlife reservoirs, such as vaccination, improved biosecurity and population management, are likely to broaden. In order to evaluate our existing control options, we must monitor the effects of interventions on TB occurrence in the affected regions of Europe and share our collective experiences.

     

Genetic structure in Red Junglefowl (Gallus gallus) populations: Strong spatial patterns in the wild ancestors of domestic chickens in a core distribution range

Red Junglefowl (Gallus gallus) are among the few remaining ancestors of an extant domesticated livestock species, the domestic chicken, that still occur in the wild. Little is known about genetic diversity, population structure, and demography of wild Red Junglefowl in their natural habitats. Extinction threats from habitat loss or genetic alteration from domestic introgression exacerbate further the conservation status of this progenitor species. In a previous study, we reported extraordinary adaptive genetic variation in the MHC B‐locus in wild Red Junglefowl and no evidence of allelic introgression between wild and domestic chickens was observed. In this study, we characterized spatial genetic variation and population structure in naturally occurring populations of Red Junglefowl in their core distribution range in South Central Vietnam. A sample of 212 Red Junglefowl was obtained from geographically and ecologically diverse habitats across an area of 250 × 350 km. We used amplified fragment‐length polymorphism markers obtained from 431 loci to determine whether genetic diversity and population structure varies. We found that Red Junglefowl are widely distributed but form small and isolated populations. Strong spatial genetic patterns occur at both local and regional scales. At local scale, population stratification can be identified to approximately 5 km. At regional scale, we identified distinct populations of Red Junglefowl in the southern lowlands, northern highlands, and eastern coastal portions of the study area. Both local and long‐distance genetic patterns observed in wild Red Junglefowl may reflect the species’ ground‐dwelling and territorial characteristics, including dispersal barriers imposed by the Annamite Mountain Range. Spatially explicit analyses with neutral genetic markers can be highly informative and here elevates the conservation profile of the wild ancestors of domesticated chickens.     

The importance of fine‐scale predictors of wild boar habitat use in an isolated population

1. Predicting the likelihood of wildlife presence at potential wildlife–livestock interfaces is challenging. These interfaces are usually relatively small geographical areas where landscapes show large variation over small distances. Models of wildlife distribution based on coarse data over wide geographical ranges may not be representative of these interfaces. High‐resolution data can help identify fine‐scale predictors of wildlife habitat use at a local scale and provide more accurate predictions of species habitat use. These data may be used to inform knowledge of interface risks, such as disease transmission between wildlife and livestock, or human–wildlife conflict.
2. This study uses fine‐scale habitat use data from wild boar (Sus scrofa) based on activity signs and direct field observations in and around the Forest of Dean in Gloucestershire, England. Spatial logistic regression models fitted using a variant of penalized quasi‐likelihood were used to identify habitat‐based and anthropogenic predictors of wild boar signs.
3. Our models showed that within the Forest of Dean, wild boar signs were more likely to be seen in spring, in forest‐type habitats, closer to the center of the forest and near litter bins. In the area surrounding the Forest of Dean, wild boar signs were more likely to be seen in forest‐type habitats and near recreational parks and less likely to be seen near livestock.
4. This approach shows that wild boar habitat use can be predicted using fine‐scale data over comparatively small areas and in human‐dominated landscapes, while taking account of the spatial correlation from other nearby fine‐scale data‐points. The methods we use could be applied to map habitat use of other wildlife species in similar landscapes, or of movement‐restricted, isolated, or fragmented wildlife populations.

     

Characterization of wild bee communities in apple and blueberry orchards

1. Wild bees provide invaluable ecosystem services in agricultural landscapes such as pollination. However, in recent decades, pollinator biodiversity, especially in wild bees, is declining on a global scale, with potentially far‐reaching consequences for crop production. Thus, there is an urgent need to determine whether wild bees are present in agricultural systems, such as fruit orchards.
2. In the present study, we examined the wild bee fauna at species and community levels during the period of bee activity (May to August) in apple and high‐bush blueberry orchards in New England.
3. Bee communities are crop‐specific and dominated by very few species, which fluctuate according to crop and season. The blueberry associated bee fauna was more diverse. In apple, communities were phylogenetically clustered at the genus level and dominated by solitary ground nesting bees within the genus Andrena. Species fluctuated widely in presence and abundance throughout the season, leading to differences in community composition and functional trait structure.
4. The results obtained in the present study show that apple and blueberry harbour a distinct and diverse bee fauna that performs vital pollination services in orchards. Our results provide essential baseline data for wild bees in blueberry and apple orchards and this can be used to improve management and conservation strategies for wild bee preservation in these crops.

     

Signatures of de‐domestication in autochthonous pig breeds and of domestication in wild boar populations from MC1R and NR6A1 allele distribution

Autochthonous pig breeds are usually reared in extensive or semi‐extensive production systems that might facilitate contact with wild boars and, thus, reciprocal genetic exchanges. In this study, we analysed variants in the melanocortin 1 receptor (MC1R) gene (which cause different coat colour phenotypes) and in the nuclear receptor subfamily 6 group A member 1 (NR6A1) gene (associated with increased vertebral number) in 712 pigs of 12 local pig breeds raised in Italy (Apulo‐Calabrese, Casertana, Cinta Senese, Mora Romagnola, Nero Siciliano and Sarda) and south‐eastern European countries (Kr?kopolje from Slovenia, Black Slavonian and Turopolje from Croatia, Mangalitsa and Moravka from Serbia and East Balkan Swine from Bulgaria) and compared the data with the genetic variability at these loci investigated in 229 wild boars from populations spread in the same macro‐geographic areas. None of the autochthonous pig breeds or wild boar populations were fixed for one allele at both loci. Domestic and wild‐type alleles at these two genes were present in both domestic and wild populations. Findings of the distribution of MC1R alleles might be useful for tracing back the complex genetic history of autochthonous breeds. Altogether, these results indirectly demonstrate that bidirectional introgression of wild and domestic alleles is derived and affected by the human and naturally driven evolutionary forces that are shaping the Sus scrofa genome: autochthonous breeds are experiencing a sort of ‘de‐domestication’ process, and wild resources are challenged by a ‘domestication’ drift. Both need to be further investigated and managed.     

Evaluating potential sources of invasive wild pigs in Ontario

Invasive wild pigs (Sus scrofa) are considered one of the most damaging species globally, and once they become established in an area, they are notoriously difficult to eliminate. As such, identifying the potential pathways of invasion, especially in places with emerging populations, is critical for preventing new or continued invasion. Wild pigs have been reported in Ontario, Canada, in recent years. We tested four nonexclusive hypotheses about the source of wild pigs in Ontario: (a) escapees from captive sources within Ontario; (b) invasion from neighboring jurisdictions; (c) existing wild populations within Ontario; and (d) translocation and illegal release. We found that sightings of Eurasian wild boar were closer to premises with wild boar than were random locations; wild boar sightings were an average of 16.3 km (SD = 25.4 km, min = 0.2 km, n = 20) from premises with wild boar. We also found that sightings of domestic pigs were closer to domestic pig farms than expected. Sightings of wild pigs in groups of more than four animals were rare. Our results suggest that wild pigs observed in Ontario are recent escapes from captivity, recognizing that there may be established groups of wild pigs that we have not yet detected. While not common, we also received reports indicating that in the past, wild pigs have been translocated and illegally released. Other North American jurisdictions that have been successful at eliminating wild pigs have removed existing populations and changed regulations to limit future invasion, such as prohibiting possession and transport of wild boar and prohibiting hunting of wild pigs.     

Genetic characterization and phylogeography of the wild boar Sus scrofa introduced into Uruguay

The European wild boar Sus scrofa was first introduced into Uruguay, in southern South America during the early decades of the last century. Subsequently, and starting from founder populations, its range spread throughout the country and into the neighbouring Brazilian state Rio Grande do Sul. Due to the subsequent negative impact, it was officially declared a national pest. The main aim in the present study was to provide a more comprehensive scenario of wild boar differentiation in Uruguay, by using mtDNA markers to access the genetic characterization of populations at present undergoing rapid expansion. A high level of haplotype diversity, intermediate levels of nucleotide diversity and considerable population differentiation, were detected among sampled localities throughout major watercourses and catchment dams countrywide. Phylogenetic analysis revealed the existence of two different phylogroups, thereby reflecting two deliberate introduction events forming distantly genetic lineages in local wild boar populations. Our analysis lends support to the hypothesis that the invasive potential of populations emerge from introgressive hybridization with domestic pigs. On taking into account the appreciable differentiation and reduced migration between locales in wild boar populations, management strategies could be effective if each population were to be considered as a single management unit.     

Maintaining genetic integrity of coexisting wild and domestic populations: Genetic differentiation between wild and domestic Rangifer with long traditions of intentional interbreeding

This study investigates the genetic effect of an indigenous tradition of deliberate and controlled interbreeding between wild and domestic Rangifer . The results are interpreted in the context of conservation concerns and debates on the origin of domestic animals. The study is located in Northeastern Zaba?kal'e, Russia at approximately 57 degrees North latitude. Blood and skin samples, collected from wild and domestic Rangifer , are analyzed for their mtDNA and microsatellite signatures. Local husbandry traditions are documented ethnographically. The genetic data are analyzed with special reference to indigenous understandings of the distinctions between local domestic types and wild Rangifer . The genetic results demonstrate a strong differentiation between wild and domestic populations. Notably low levels of mtDNA haplotype sharing between wild and domestic reindeer, suggest mainly male‐mediated gene flow between the two gene pools. The nuclear microsatellite results also point to distinct differences between regional domestic clusters. Our results indicate that the Evenki herders have an effective breeding technique which, while mixing pedigrees in the short term, guards against wholesale introgression between wild and domestic populations over the long term. They support a model of domestication where wild males and domestic females are selectively interbred, without hybridizing the two populations. Our conclusions inform a debate on the origins of domestication by documenting a situation where both wild and domestic types are in constant interaction. The study further informs a debate in conservation biology by demonstrating that certain types of controlled introgression between wild and domestic types need not reduce genetic diversity.     

Ecotypic differentiation reveals seed colour‐related alkaloid content in a crop wild relative

• Crop wild relatives can be a useful source of genotypes that maximise crop survival and yield in specific habitats. Lupinus angustifolius is an annual forb with crop varieties derived from a narrow genetic basis but that are cultivated worldwide. Its seeds have high nutritional value, but they naturally contain alkaloids with anti‐nutritive factors. The study of its wild populations can be useful to find genotypes that contribute to higher climate resilience and greater yield under stressing environmental conditions.
• Using a common garden, we evaluated ecotypic differentiation in four natural populations from two contrasting latitudes in terms of plant biomass, seed mass and number, alkaloid content in seeds for the three main alkaloids present in the plant and seed colour, including its possible influence on post‐dispersal predation. Correlations among traits were also assessed.
• We found differences among populations for all traits except final biomass. Northern populations had lighter seeds and a tendency to yield more seeds when they produced white seeds, compared to southern populations and variegated seeds. Regardless of latitude, populations showed differences in alkaloid concentration, with all three alkaloids found generally in high or low concentrations in each population. Proportion of white seed morphs varied in each population. Seed colour did not influence predator preference. In addition, white seed colour was related to a low alkaloid content.
• Our results evidence the existence of natural ecotypic differentiation in L. angustifolius not only due to latitudinal range, but also to local environmental factors. White seed coat colour could be used as a visual clue for identification of low‐alkaloid genotypes, a priority trait in L. angustifolius breeding programmes.

     

Biogeographical variation in the population density of wild boar (Sus scrofa) in western Eurasia

Aim We reviewed 54 studies reporting population densities of wild boar (Sus scrofa) in western Eurasia in order to investigate the roles of vegetation productivity [fraction of photosynthetically active radiation (FPAR) index], winter harshness (mean January temperature) and presence/absence of wolves (Canis lupus) in shaping the biogeographical variation in population density of wild boar. Location We collected published data on the autumn–winter population density of wild boar (number of individuals km^?2) in 54 locations in western Eurasia, from 1966 to 2003. Methods The mean January temperature, obtained from the World Climate data base ( http://www.worldclimate.com ), was taken as a measure of winter severity. We used monthly 4 × 4 km MODIS FPAR data sets covering January 2000 to June 2004 to calculate the vegetation productivity index. In addition, we collected literature data about the presence or absence of wolves from the study areas. Results In the geographical span of 37–60° N, the population densities of wild boar declined by three orders of magnitude, from 10 to 0.01 individuals km^?2. The best multiple regression model (selected with the Akaike information criterion corrected for small samples) showed that mean January temperature and the vegetation productivity index were the most important factors explaining the biogeographical variation in population densities of wild boar. The impact of temperature was stronger than that of productivity. The presence of wolves had a weak limiting effect on population densities of wild boar at the biogeographical scale. Main conclusion We propose that winter harshness imposes density‐independent mortality on wild boar populations at higher latitudes. Competition for food in less productive regions may cause stronger density dependence in birth and death rates of wild boar populations. We expect that wild boar will respond to global warming by both an increase in local population densities and an expansion of their geographical range north and north‐eastwards.