Massimo Scandura

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.

A comparative analysis of wolf (Canis lupus) diet in three different Italian ecosystems

Summary To verify food habit flexibility of wolf populations under different ecological conditions, scats collected year round were analysed in three study areas and diet composition of resident packs was compared. The three study areas, representing Alpine (SV), Apennine (PM) and Mediterranean (CV) ecosystems, are rich in wild ungulates, which differ in number of species and relative abundance; livestock is also present. Wild ungulates were the main source of food, accounting for 89.4%–95.1% of the diet. Livestock, instead, scarsely reached 8% of annual mean percent volume in any one area, and only in the Alps did they play a major role in autumn. Other food items constituted less than 5% of annual mean percent volume. Variations in the proportions of use of wild ungulate categories were observed among the study areas, although some patterns of intraspecific selection emerged in each area. Finally, differences both in the relationships between utilisation and availability of preys, and in trophic niche breadth were discussed in relation to environmental features and colonization patterns.

FEMALE-FEMALE CONFLICT IN THE HAREM OF A SNAIL CICHLID (LAMPROLOGUS OCELLATUS): BEHAVIOURAL INTERACTIONS AND FITNESS CONSEQUENCES

Female intra-sexual competition plays an important role in the settlement process during pair or harem formation and in established harems of Lamprologus ocellatus , a small snail shell inhabiting cichlid from Lake Tanganyika. Larger females settle first and this could partly be due to male preference for larger females as shown in simultaneous choice tests but is also due to dominance of the larger female. Smaller females were unable to settle close to a larger one. Even when snail shells were not limiting the smaller was either unable to settle or had to settle at a considerable distance. This effect was independent of prior residence. Intense female-female aggression suggests that close settlement is disadvantageous to females. Genetic analyses of maternity using microsatellite length polymorphism at five loci showed a reproductive skew between females in a harem. Additionally, it proved brood mixing in aquaria as well as in the field. Brood mixing can be detrimental to female breeding success through interbrood cannibalism if size difference of juveniles amounts to 5 mm. Territoriality of juveniles, shown even between same-sized siblings, may cause indirect mortality through earlier dispersal of young. Females rejected experimentally added larger juveniles but accepted young smaller than their own fry. Acceptance of smaller juveniles could be advantageous through a dilution of predator attacks but it also appears to induce costs since females with young at the shell do not rear another brood. Large median distances of 91 cm maintained aggressively between breeding females in the field may serve to minimize the adverse effects of breeding in a harem.

Effects of human perturbation on the genetic make-up of an island population: the case of the Sardinian wild boar

Game species are often manipulated by human beings, whose activities can deeply affect their genetic make-up and population structure. We focused on a geographically isolated wild boar population (Sardinia, Italy), which is classified, together with the Corsican population, as a separate subspecies (Sus scrofa meridionalis). Two hundred and ten wild boars collected across Sardinia were analysed with a set of 10 microsatellites and compared with 296 reference genotypes from continental wild populations and to a sample of domestic pigs. The Sardinian population showed remarkable diversity and a high proportion of private alleles, and strongly deviated from the equilibrium. A Bayesian cluster analysis of only the Sardinian sample revealed a partition into five subpopulations. However, two different Bayesian approaches to the assignment of individuals, accounting for different possible source populations, produced consistent results and proved the admixed nature of the Sardinian population. Indeed, introgressive hybridization with boars from multiple sources (Italian peninsula, central Europe, domestic stocks) was detected, although poor evidence of crossbreeding with free-ranging domestic pigs was unexpectedly found. After excluding individuals who carried exotic genes, the population re-entered Hardy–Weinberg proportions and a clear population structure with three subpopulations emerged. Therefore, the inclusion of introgressed animals in the Bayesian analysis implied an overestimation of the number of clusters. Nonetheless, two of them were consistent between analyses and corresponded to highly pure stocks, located, respectively, in north-west and south-west Sardinia. This work shows the critical importance of including adequate reference samples when studying the genetic structure of managed wild populations.

Selection of rendezvous sites and reuse of pup raising areas among wolves Canis lupus of north-eastern Apennines, Italy

A coarse scale analysis was carried out of factors affecting rendezvous site selection and fidelity to pup raising areas in wolfCanis lupus Linnaeus, 1758 packs inhabiting the north eastern Apennines, Italy. From 1993 to 2004, 44 rendezvous sites were identified, and compared with random sites for variables related to topography, habitat, and human presence. Rendezvous sites were significantly more frequent inside protected areas and at a significantly greater distance from paved roads and villages than random sites. Moreover, they were located on a significantly steeper slope and at a higher absolute elevation than random sites, whereas we did not observe selection of a particular aspect. Deciduous forests were selected, whereas open areas were not used. Canopy cover above 70% was positively selected. Distance from protected areas border and paved roads, and presence of deciduous forest proved the main factors affecting rendezvous site distribution. In four cases we observed the reuse of the same rendezvous sites for two consecutive years. Some packs tended to locate their rendezvous sites in small portions of their territory, thus implying that some areas are more suitable for pup raising.

Temporal changes of howling in south European wolf packs

Abstract Howling was elicited in three wolf packs, monitored on the Italian Apennines, between 1996 and 2000. To test their attitude to reply to extraneous individuals, wolves were stimulated by playback of tape‐recorded howls emitted from prominent sites. Responses were recorded and processed by sonographic analysis, discriminating between choral and single replies, and evaluating the presence/absence of cubs. The overall reply rate was 12.6%. Responsiveness was high during late summer‐early fall, a period coinciding with abandonment of the den and translocation of the litter to rendezvous sites. At this time, chorus howling represented the majority of total replies, and the quickness of responses suggests a higher bent to vocalize. Throughout the year, late evening and dawn were the parts of the day at which wolves showed the maximum tendency to respond.

Long-Lasting, Kin-Directed Female Interactions in a Spatially Structured Wild Boar Social Network

Individuals can increase inclusive fitness benefits through a complex network of social interactions directed towards kin. Preferential relationships with relatives lead to the emergence of kin structures in the social system. Cohesive social groups of related individuals and female philopatry of wild boar create conditions for cooperation through kin selection and make the species a good biological model for studying kin structures. Yet, the role of kinship in shaping the social structure of wild boar populations is still poorly understood. In the present study, we investigated spatio-temporal patterns of associations and the social network structure of the wild boar Sus scrofa population in Białowieża National Park, Poland, which offered a unique opportunity to understand wild boar social interactions away from anthropogenic factors. We used a combination of telemetry data and genetic information to examine the impact of kinship on network cohesion and the strength of social bonds. Relatedness and spatial proximity between individuals were positively related to the strength of social bond. Consequently, the social network was spatially and genetically structured with well-defined and cohesive social units. However, spatial proximity between individuals could not entirely explain the association patterns and network structure. Genuine, kin-targeted, and temporarily stable relationships of females extended beyond spatial proximity between individuals while males interactions were short-lived and not shaped by relatedness. The findings of this study confirm the matrilineal nature of wild boar social structure and show how social preferences of individuals translate into an emergent socio-genetic population structure.

An empirical approach for reliable microsatellite genotyping of wolf DNA from multiple noninvasive sources

Wildlife management and conservation take advantage of the possibility to study free-living populations by collecting and analysing noninvasive samples. Nevertheless, the commonly adopted approaches, aimed at preventing results being affected by genotyping errors, considerably limit the applicability of noninvasive genotyping. An empirical approach is presented for achieving a reliable data set of wolf (Canis lupus) genotypes from multiple sources of DNA collected in a monitored population. This method relies on the relationship between sample quality and amplification outcome, which is ultimately related to the occurrence of typing errors (allelic dropout, false alleles). After DNA extraction, templates are amplified once at each locus and a conservative rating system (Q-score) is adopted to define the quality of single-locus amplifications. A significant relationship was found between quality scores and error rate (ER) (r2=0.982). Thus it was possible to predict the chance a genotype has of being affected by errors on the basis of its Q-score. Genotypes not reaching a satisfactory confidence level can either be replicated to become reliable or excluded from the data set. Accordingly, in the present case study, 48–73% of all single-locus and 51–53% of all multilocus (ML) genotypes reached a sufficient (99 and 95%, respectively) reliability level after a single amplification per locus. Despite the possible decrease in overall yield, this method could provide a good compromise between accuracy in genotyping and effectiveness in screening large data sets for long-term or large-scale population surveys. However, to achieve complete and reliable data sets, replicated amplifications are necessary for those samples and loci providing poor results.

Nonkin Associations in Wild Boar Social Units

Abstract We investigated the social organization of wild boars (Sus scrofa) using genetic and spatial data from a study population in Tuscany, Italy. In total, 120 wild boars of different sexes and age classes were captured and monitored from 2002 to 2006. All of them were genetically analyzed by using 10 polymorphic microsatellites (HE  =  0.693, k  =  6.6) and a matrix of pairwise relatedness was calculated. In addition, a reference sample of fully related individuals was created by genotyping 11 adult females and their fetuses (n  =  56). Spatial data were gathered for 65 animals that had been fitted with either radiocollars or ear transmitters. Sixteen social units were identified by capture data and confirmed by observations and telemetry. A correlation between interindividual spatial distance and relatedness was observed only in summer–early autumn and seemed to be associated to the presence of piglets. The prediction of matrilinearity in wild boar social units was not confirmed, because a low degree of relatedness among boars was observed within groups. Aggregations of unrelated adult females (with their litters) were detected in the study population. The high turnover in the population due to human-caused mortality seems to be the main factor responsible for this altered social structure. Accordingly, we suggest that the observed social organization would result from grouping of unrelated survivors that is promoted by the presence of wolves in the area.

Fine-scale genetic structure suggests low levels of short-range gene flow in a wolf population of the Italian Apennines

We investigated local gene flow in a high-density wolf (Canis lupus) population of the Italian Apennines, where no effective barrier to wolf dispersal was present. From 1998 to 2004 we examined wolf carcasses and non-invasively collected samples, focusing on three mountain districts, separated by two valleys, where wolf packs showed high spatial stability. Using nine autosomal microsatellites we successfully genotyped 177 samples, achieving the identification of 74 wolves. Genetic relatedness steeply decreased with increasing distance between sampling areas, thus suggesting that short-distance interpack migration is infrequent in this population. In addition, no individual from a central pack under intensive monitoring was sampled in the range of the surrounding packs over a 4-year period. The limited short-distance gene flow resulted in a cryptic genetic structure, which was revealed by Bayesian analysis. A different genetic cluster was found in each of the three mountain areas, and a small proportion of first-generation immigrants was detected. Overall, the present study suggests that local genetic differentiation in Italian wolves might arise from high spatial stability of packs and can be favoured by a combination of long-range dispersal, the attitude to mate between unrelated individuals and a high young mortality rate.