Ancient Mitochondrial DNA Reveals the Origin of Sus scrofa from Rebun Island, Japan

The Kabukai A site (5 to 8C A.D.) of the Okhotsk cultural area is on Rebun Island, a small island near the coast, north–northwest of Hokkaido, Japan. Specimens of Sus scrofa, called the Sakhalin pig, were discovered in five cultural layers at the Kabukai A site. Ancient DNA was extracted from the remains of 42 Sakhalin pig bones. Thirty-nine nucleotide sequences of the 574-bp mitochondrial DNA control region, estimated to have originated from at least 21 individuals, were amplified and analyzed phylogenetically. Nine distinct haplotypes (A1, A2, A3, B1, B2, C1, C2, D1, and D2) from this site were classified into four haplotype groups (A, B, C, and D) by parsimonious network analysis. Phylogenetic analysis of 9 ancient and 55 modern haplotypes indicated that the population of Sakhalin pigs at the Kabukai A site belonged to two distinct clusters; haplotype groups A and B formed a cluster comprised only of themselves, and haplotype groups C and D belonged to the cluster of one of the two genetic groups of Japanese wild boars uniquely distributed in the western part of Japan, including one northeast Mongolian wild boar. Analysis of the haplotype distribution among three archaeological sites and their historical transitions among the five layers reflecting the cultural periods at the Kabukai A site suggests that the Sakhalin pig populations were introduced from Sakhalin island and the Amur River basin in the northeastern Eurasian continent together with some cultural influences. Received: 18 April 2000 / Accepted: 24 November 2000     

Genetic relationship and distribution of the Japanese wild boar (Sus scrofa leucomystax) and Ryukyu wild boar (Sus scrofa riukiuanus) analysed by mitochondrial DNA

Mitochondrial genetic variations were used to investigate the relationships between two Japanese wild boars, Japanese wild boar (Sus scrofa leucomystax) and Ryukyu wild boar (S.s. riukiuanus). Nucleotide sequences of the control (27 haplotypes) and cytochrome b (cyt-b) regions (19 haplotypes) were determined from 59 Japanese wild boars, 13 Ryukyu wild boars and 22 other boars and pigs. From phylogenetic analyses, the mtDNA of Ryukyu wild boar has a distinct lineage from that of Japanese wild boar, which was classified into the Asian pig lineage. This result suggests that the Ryukyu wild boar has a separate origin from the Japanese wild boar.     

Phylogeography and population structure of the Japanese wild boar Sus scrofa leucomystax: mitochondrial DNA variation

Phylogeographic characteristics and population structure of Japanese wild boar (Sus scrofa leucomystax) were investigated using mitochondrial DNA (mtDNA) sequence data. Sixteen Japanese wild boar haplotypes detected from partial sequences of the mtDNA control region (574-bp) from 180 Japanese wild boar specimens from 10 local populations on Honshu, Shikoku, and Kyushu islands and 41 haplotypes from other S. scrofa were analyzed using the neighbor-joining method. The Japanese wild boars were more closely related to Northeast Asian wild boars from Mongolia than to the other Asian continental S. scrofa. The Japanese and Northeast Asian wild boars were not significantly distinguished by corrected average pairwise difference analysis. The ancestors of Japanese wild boars are suggested to have been part of the continental S. scrofa population that spread from Southeast to Northeast Asia during the Middle to Late Pleistocene. The Japanese wild boar mtDNA haplotype cladogram shows 95% parsimoniously plausible branch connections supporting three sympatric clades. Nested clade analysis indicates that these three clades are the result of distinct historical events or gene flow. The present population of Japanese wild boars may have been formed by a few independent migrations of distinct clades from the continent with subsequent mixing on the Japanese Islands.     

The robust phylogeny of Korean wild boar (<Emphasis Type="Italic">Sus scrofa coreanus</Emphasis>) using partial D-loop sequence of mtDNA

In order to elucidate the precise phylogenetic relationships of Korean wild boar (Sus scrofa coreanus), a partial mtDNA D-loop region (1,274 bp, NC_000845 nucleotide positions 16576-1236) was sequenced among 56 Korean wild boars. In total, 25 haplotypes were identified and classified into four distinct subgroups (K1 to K4) based on Bayesian phylogenetic analysis using Markov chain Monte Carlo methods. An extended analysis, adding 139 wild boars sampled worldwide, confirmed that Korean wild boars clearly belong to the Asian wild boar cluster. Unexpectedly, the Myanmarese/Thai wild boar population was detected on the same branch as Korean wild boar subgroups K3 and K4. A parsimonious median-joining network analysis including all Asian wild boar haplotypes again revealed four maternal lineages of Korean wild boars, which corresponded to the four Korean wild boar subgroups identified previously. In an additional analysis, we supplemented the Asian wild boar network with 34 Korean and Chinese domestic pig haplotypes. We found only one haplotype, C31, that was shared by Chinese wild, Chinese domestic and Korean domestic pigs. In contrast to our expectation that Korean wild boars contributed to the gene pool of Korean native pigs, these data clearly suggest that Korean native pigs would be introduced from China after domestication from Chinese wild boars.     

The development of the gene pool in the microevolution of <Emphasis Type="Italic">Sus scrofa</Emphasis> and the role of heterozygosity in the breed-forming process

The gene pool formation of the modern domestic breeds of pig Sus scrofa domestica and their genesis based on hybridization of wild ancestral forms of the European and Asian origin were studied using molecular immunogenetic methods. Males of the European and Central Asian S. scrofa subspecies (S. s. scrofa and S. s. nigripes were hybridized with domestic pigs of the Swedish Landrace and Vietnamese Black Masked breeds. In addition, we examined the genotypic structure of 65 wild, aboriginal, and local populations as well as cultured breeds, including the stock breeds with different levels of selection. Frequencies of alleles and suballelles of the chromosome 4 locus controlling antigens of the L blood group system were analyzed. The origin of marker suballeles of the European and Asian origin was estimated in the most widespread world pig breeds. Unexpectedly, a strikingly high frequency of the Asian elements was found in the most productive European and American breeds, as well as in the best breeds of Russia and other CIS countries. Only one form of heterozygosity (bcgi/bdfi) was found in a population of wild European ancestors, whereas domestic pig breeds displayed heterozygosity for far more numerous suballeles of the locus studied. Animals with heterozygosity for alleles of the European and Asian origin showed higher adaptivity and fertility.__________Translated from Genetika, Vol. 41, No. 4, 2005, pp. 566–576.Original Russian Text Copyright © 2005 by Tikhonov.     

Prehistoric Sado Island populations of Sus scrofa distinguished from contemporary Japanese wild boar by ancient mitochondrial DNA

Ancient mitochondrial DNA (mtDNA) mainly from Jomon Period Sus scrofa bone specimens (6,100-1,700 years old) was examined to clarify the genetic relationships between prehistoric and contemporary S. scrofa on Hokkaido, Honshu, Sado, and Izu islands of the Japanese Archipelago. Phylogenetic analysis of the mtDNA control region (574 bp) and analysis of pairwise nucleotide differences between prehistoric and contemporary S. scrofa sequences showed the following relationships between these groups: (1) a group genetically similar to contemporary Japanese wild boars was found mainly on Honshu Island, Hokkaido Island, and the Izu Islands, and (2) a monophyletic group distinct from contemporary Japanese wild boars was found on Sado Island. These results suggest that prehistoric people introduced S. scrofa from Honshu Island to Hokkaido Island and the Izu Islands. The estimated divergence times between the prehistoric Sado group and the other prehistoric S. scrofa is approximately congruent with the geological isolation of Sado Island from Honshu Island. Our results suggest that this extinct S. scrofa population was present on Sado Island as recently as around 2,000 years ago.     

A Phylogenetic Study of the Origin of the Domestic Pig Estimated from the Near-Complete mtDNA Genome

The near-complete pig mtDNA genome sequence (15,997 bp) was determined from two domestic pigs (one Chinese Meishan and one Swedish Landrace) and two European wild boars. The sequences were analyzed together with a previously published sequence representing a Swedish domestic pig. The sequences formed three distinct clades, denoted A, E1, and E2, with considerable sequence divergence between them (0.8–1.2%). The results confirm our previous study (based on the sequence of the cytochrome B gene and the control region only) and provide compelling evidence that domestication of pigs must have occurred from both an Asian and a European subspecies of the wild boar. We estimated the time since the divergence of clade A (found in Chinese Meishan pigs) and E1 (found in European domestic pigs) at about 900,000 years before present, long before domestication about 9000 years ago. The pattern of nucleotide substitutions among the sequences was in good agreement with previous interspecific comparisons of mammalian mtDNA; the lowest substitution rates were observed at nonsynonymous sites in protein-coding genes, in the tRNA and rRNA genes, while the highest rates were observed at synonymous sites and in the control region. The presence of Asian clade A in some major European breeds (Large White and Landrace) most likely reflects the documented introgression of Asian germplasm into European stocks during the 18th and 19th centuries. The coexistence of such divergent mtDNA haplotypes for 100+ generations is expected to lead to the presence of recombinant haplotypes if paternal transmission and recombination occur at a low frequency. We found no evidence of such recombination events in the limited sample studied so far. Received: 19 April 2000; Accepted: 15 November 2000     

Geographic population structure and sequence divergence in the mitochondrial DNA control region of the Japanese wild boar (Sus scrofa leucomystax), with reference to those of domestic pigs

Mitochondrial DNA (mtDNA) control regions from 40 Japanese wild boars were examined by direct sequencing after amplification by PCR. From the DNA sequences obtained, we found eight haplotypes, whose differences arose via transitions. The geographical distribution of these different haplotypes indicated that wild boar populations inhabited limited areas and that there was some restricted gene flow between local populations. Eight mtDNA haplotypes from Eastern and Western domestic pigs and the Ryukyu wild boar were also analyzed as references to those from Japanese wild boars. The cluster analyses of the control-region sequences showed that those from Japanese wild boards belong to the Asian type as do those from Eastern domestic pigs and the Ryukyu wild boar, which differed from the European type (Western domestic pigs).     

东北亚地区野猪种群mtDNA遗传结构及系统地理发生

研究测定了中国东北、华北及四川西部72个野猪(Susscrofa)个体线粒体控制区全序列,并结合GenBank报道的日本野猪(S.s.leucomystax)、琉球野猪(S.s.riukiuanus)72个同源区序列,分析了东北亚地区野猪线粒体DNA的变异及系统地理格局。在东北亚地区野猪的线粒体控制区共发现42个变异位点,均为转换,共定义了34个单元型。单元型之间的系统发生分析表明,东北亚地区野猪来自同一祖先。东北亚地区野猪现生种群具有显著的种群遗传结构,其中日本野猪与分布于中国东北地区的东北野猪之间亲缘关系较近;而琉球野猪则与华北野猪间亲缘关系较近,与日本野猪和东北野猪间的关系相对较远。嵌套进化枝系统地理分析(Nestedcladephylogeographicalanalysis,NCPA)表明:东北亚地区野猪由同一祖先经过长距离的迁徙而形成现生各种群(或亚种);琉球野猪应起源于大陆野猪,其种群演化可能经历了片断化事件;华北野猪呈现南部种群遗传多样性高的特点,其种群内部曾经历了一次分布区由南向北的扩张     

Chromosome translocations in the karyotypes of wild boars Sus scrofa L. of the European and the Asian areas of USSR

Summary The karyotypes of the 80 wild boars of the four subspecies, Sus scrofa ussuricus Heude from the Far East of USSR, S. s. nigripes Blanf. from Kirghizia (the Middle Asia), S. s. attila Thos. from Azerbaijan, S. s. ferus from Lithuania, Byelorussia and Central Russia, and the 44 domestic pigs of the five different breeds (Vietnamese Black, Siberian Omskaja Gray, Kakhethian-aborigen Georgian, Mangalica Hungarian, Landrace Swedish), were studied by the Giemsa Banding Method. Differential staining by the G-Method made it possible to identify all the homologous chromosomes of the wild and domestic pig karyotypes as well as to reveal the polymorphism of wild boar karyotypes (2n = 36, 37 and 38), which are determined by the two types of chromosome translocation. Crosses between domestic pigs (2n = 38) and wild boars (2n = 36 and 37) with different chromosome rearrangements might help to clarify the genetic function of the chromosomes A4, B3, B4, B5 and allow their use as genetic markers.     

Riding the Kuroshio Current: Stepping stone dispersal of the Okinawa tree lizard across the East Asian Island Arc

Aim

Located hundreds of kilometres offshore of continental mainland Asia, the extremely high level of land vertebrate endemism in the East Asian Island Arc provides an excellent opportunity to test hypotheses regarding biogeographic processes and speciation. In this study, we aim to test alternative explanations for lineage diversification (vicariance versus dispersal models), and further develop a temporal framework for diversification in our focal taxon, which is consistent with the known age of these islands. We achieve these tests by investigating the historical biogeography of the Okinawa tree lizard (Japalura polygonata), one of the few widely‐distributed reptiles across this archipelago.

Location

The East Asian Island Arc: (1) Central Ryukyu (Amami and Okinawa groups); (2) Southern Ryukyu (Miyako and Yaeyama groups); (3) Taiwan and adjacent islands.

Methods

A total of 246 tissues were sampled from 10 localities in the Ryukyu archipelago and 17 localities in Taiwan, covering the entire distributional range of this species, including all subspecies. DNA sequences of the mitochondrial cytochrome b, 16S ribosomal RNA, nuclear BACH‐1 and RAG‐1 genes (total: 4,684 bp) were obtained from these samples. We used maximum likelihood and Bayesian methods to infer phylogeny and divergence time, and used a model‐fitting method of biogeographical inference to estimate ancestral range evolution.

Results

Multiple lines of evidence combine to identify a general pattern of dispersal‐mediated diversification northward through the archipelago, following initial dispersal from Taiwan. These included (1) a phylogenetic estimate, revealing a sequential, south‐to‐north branching pattern; (2) ancestral range estimation, inferring multiple overseas dispersals and subsequent colonization of new landmasses; and (3) a reduction in genetic variation observed in successively‐diverging lineages, decreasing from Taiwan northward, towards more remote islands. These results provide strong statistical support for an interpretation of successive bouts of dispersal via the powerful, well‐documented, south‐to‐north Kuroshio Current. Estimation of divergence times suggests that most clades in southern Ryukyu and Taiwan diverged early, giving rise to lineages that have remained isolated, and that more recently‐diverged lineages then colonized northward to subsequently occupy the landmasses of the Central Ryukyu archipelago.

Main conclusions

Our general inference of biogeographic history in Japalura polygonata suggested that this species originated on Taiwan and the Yaeyama group, and arrived at its current distribution in Miyako, Okinawa, Toku and Amami islands by a series of stepping‐stone dispersals, which we report for the first time for a terrestrial vertebrate endemic to this region.     

Serosurveillance for selected infectious disease agents in wild boars (Sus scrofa) and outdoor pigs in Switzerland

The large abundance of free-ranging wild boars (Sus scrofa) and a trend towards animal friendly outdoor management of domestic pigs lead to an increasing probability of disease transmission between those animal populations. In 2001, an active monitoring was started for classical swine fever (CSF), Aujeszky’s disease (AD) and porcine brucellosis (PB) in wild boars in Switzerland. The objective of this programme was to document the serological status of wild boars regarding the selected pathogens. To continue this serosurveillance, 1,060 wild boar samples were collected during two regular hunting seasons in 2004–2005. Furthermore, in a pilot study, 61 outdoor pigs from 14 farms located in areas with high wild boar densities were sampled in 2004 and serologically tested for AD and PB. All wild boar samples were negative for CSF. Seroprevalence for AD was 2.83% (95% CI 1.91–4.02%). Seroprevalence for PB was 13.5% (95% CI 10.7–16.7%) for the Rose Bengal test and 11.05% (95% CI 8.82–13.61%) for the indirect ELISA. There was no serological evidence for AD in domestic pigs. All tested animals from 13 piggeries were seronegative for PB, but three pigs from the same farm showed doubtful results. Further investigations on the farm did not indicate the presence of PB in the herd. These findings urge the need for better diagnostic tools to obtain reliable results concerning PB prevalence. Since contact and following transmission of infectious agents between infected wild boars and outdoor pigs might occur in the future, it is advisable to include outdoor pigs in areas at risk in routine surveillance programmes.     

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.     

Phenotype and animal domestication: A study of dental variation between domestic,wild, captive,hybrid and insular Sus scrofa

Background

Identifying the phenotypic responses to domestication remains a long-standing and important question for researchers studying its early history. The great diversity in domestic animals and plants that exists today bears testament to the profound changes that domestication has induced in their ancestral wild forms over the last millennia. Domestication is a complex evolutionary process in which wild organisms are moved to new anthropogenic environments. Although modern genetics are significantly improving our understanding of domestication and breed formation, little is still known about the associated morphological changes linked to the process itself. In order to explore phenotypic variation induced by different levels of human control, we analysed the diversity of dental size, shape and allometry in modern free-living and captive wild, wild x domestic hybrid, domestic and insular Sus scrofa populations.

Results

We show that domestication has created completely new dental phenotypes not found in wild boar (although the amount of variation amongst domestic pigs does not exceed that found in the wild). Wild boar tooth shape also appears to be biogeographically structured, likely the result of post-glacial recolonisation history. Furthermore, distinct dental phenotypes were also observed among domestic breeds, probably the result of differing types and intensity of past and present husbandry practices. Captivity also appears to impact tooth shape. Wild x domestic hybrids possess second molars that are strictly intermediate in shape between wild boar and domestic pigs (third molars, however, showing greater shape similarity with wild boar) while their size is more similar to domestic pigs. The dental phenotypes of insular Sus scrofa populations found on Corsica and Sardinia today (originally introduced by Neolithic settlers to the islands) can be explained either by feralization of the original introduced domestic swine or that the founding population maintained a wild boar phenotype through time.

Conclusions

Domestication has driven significant phenotypic diversification in Sus scrofa. Captivity (environmental control), hybridization (genome admixture), and introduction to islands all correspond to differing levels of human control and may be considered different stages of the domestication process. The relatively well-known genetic evolutionary history of pigs shows a similar complexity at the phenotypic level.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-014-0269-x) contains supplementary material, which is available to authorized users.     

Detection of hybrids between wild boars (Sus scrofa scrofa) and domestic pigs (Sus scrofa f. domestica) in Greece,using the PCR-RFLP method on melanocortin-1 receptor (MC1R) mutations

The melanocortin-1 receptor (MC1R) regulates melanogenesis in mammals within the mammalian melanocyte and the hair follicle. Common variations (polymorphisms) in the MC1R gene are associated with normal differences in skin and hair colour. So far, a unique MC1R allele (E+) has been identified in European wild boar (Sus scrofa scrofa), associated with the wild-type coat colour (variable shades of brown) that is not found in any of the domestic breeds. In addition, a series of alleles found in pigs, some of which observed only in particular breeds, have been proposed as markers in breed traceability systems. The current study is an attempt to detect possible hybrids between wild boars and domestic pig breeds as well as to identify races of pig that are not purebred. For this purpose, wild boars were analysed against Large White pigs, applying the PCR-restriction fragment length polymorphism (RFLP) method. A high percentage (16.7%) of hybrids was detected within a breeding station compared with the percentage of hybrids within the populations of free-ranging wild boar (5.0%). These results should be taken into consideration for future restocking operations to avoid the chance of outbreeding depression, which is more intense when local populations are introgressed by gene pools from domesticated, usually inbred, animals.     

Inferring the origin and genetic diversity of the introduced wild boar (<Emphasis Type="Italic">Sus scrofa</Emphasis>) populations in Argentina: an approach from mitochondrial markers

The Eurasian wild boar (Sus scrofa Linnaeus, 1758) was introduced into Argentina at the beginning of the twentieth century when individuals from Europe were taken to La Pampa province for hunting purposes. Starting from there, a dispersal process began due to the invasive characteristics of the species and to human-mediated translocations. The main objective of this study was to characterize for the first time, the phylogenetic relationships among wild boars from Argentina with those from Uruguay, Europe, Asia, and the Near East, along with diverse domestic pig breeds in order to corroborate the historical information about the origin of the local populations. To this end, we used mitochondrial Control Region and Cytochrome b sequences from sampled Argentinian wild boars and retrieved from GenBank. The results showed that the majority of the Argentinian wild boar populations descend from European lineages, in particular of the E1 clade, according to the historical records. Remarkably, the population of El Palmar National Park had Asian origin that could be attributed to hybridization with local domestic pigs or to unrecorded translocations. Finally, genetic diversity in Argentinian populations was lower than in Europe and Uruguay meaning that wild boar in Argentina is still under the influence of founder effect and has experienced minor genetic introgression from domestic pigs, representing in this sense a reservoir of the original wild boar genetic variability.     

Detection and genetic characterization of porcine circovirus 2 isolates from the first cases of postweaning multisystemic and wasting syndrome in wild boars in Greece

In 2002, postweaning multisystemic wasting syndrome (PMWS) was diagnosed in a European female wild boar (Sus scrofa), based on the detection of porcine circovirus 2 (PCV2) DNA in various organs, including the uterus, and on histopathologic lesions. This is the first detection of PCV2 DNA in the uterus of a wild boar. Three years later (2005), a wild boar < 6-8 mo of age was found moribund. It presented wasting and dyspnea and finally died. PCV2 DNA was detected in tissue samples, and histopathologic lesions consistent with PMWS were observed. Both wild boars were from neighboring hunting areas in central Greece. Two PCV2 strains from the wild boars were genetically characterized and compared to other reported PCV2 sequences from wild boars and domestic pigs. The PCV-2 sequences from the wild boars in this study were closely related to each other and were grouped with two isolates from wild boars from Hungary. The phylogenetic analysis revealed that the virus might be transmitted between hunting areas. In addition, PCV2 may spread from domestic pigs to wild boars and vice versa.     

A genetic analysis of the Sakishima islanders reveals no relationship with Taiwan aborigines but shared ancestry with Ainu and main‐island Japanese

The Sakishima islands are members of the Ryukyu island chain, stretching from the southwestern tip of the Japanese archipelago to Taiwan in the East China Sea. Archaeological data indicate cultural similarities between inhabitants of prehistoric Sakishima and Neolithic Taiwan. Recent studies based on tooth crown traits show remarkably high inter‐island diversity among Ryukyu islanders, suggesting that the Sakishima islanders might have genetic backgrounds distinct from main‐island Okinawa people. To investigate the genetic diversity of the Ryukyu islanders, we analyzed mtDNA, Y chromosome, and autosomal short tandem repeat loci in a sample of main‐island Okinawa people and Sakishima (Miyako and Ishigaki) islanders whose participated in a previous study of tooth crown morphology. Our phylogenetic analysis of maternal (mtDNA) and paternal (Y chromosome) lineages shows that the Sakishima islanders are more closely related to people from the Japanese archipelago than to Taiwan aborigines. Miyako islanders and the Hokkaido Ainu have the first and second highest frequencies (respectively) of the Y‐chromosomal Alu‐insertion polymorphism, which is a presumable Jomon marker. Genetic diversity statistics show no evidence of demographic reduction or of extreme isolation in each island's population. Thus, we conclude that 1) Neolithic expansion from Taiwan did not contribute to the gene pool of modern Sakishima islanders, 2) male‐lineage of the Ryukyu islanders likely shares a common ancestor with the Hokkaido Ainu who are presumably direct descendants of the Jomon people, and 3) frequent reciprocal gene flow among islands has masked the trace of common ancestry in the Ryukyu island chain. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

Wild boar: an increasing concern for Aujeszky's disease control in pigs?

Background  

The goal of this study was describing the temporal evolution of Aujeszky's disease virus (ADV) contact prevalence among Eurasian wild boar (Sus scrofa) populations under different management regimes and contact likelihoods with domestic pigs. Given the recent increase in wild boar abundance throughout Europe, we hypothesized that wild boar contact with ADV would remain stable in time even after significant reduction of ADV prevalence in domestic pigs.     

Structural Classification of Wild Boar (Sus scrofa) Vocalizations

Determining whether a species' vocal communication system is graded or discrete requires definition of its vocal repertoire. In this context, research on domestic pig (Sus scrofa domesticus) vocalizations, for example, has led to significant advances in our understanding of communicative functions. Despite their close relation to domestic pigs, little is known about wild boar (Sus scrofa) vocalizations. The few existing studies, conducted in the 1970s, relied on visual inspections of spectrograms to quantify acoustic parameters and lacked statistical analysis. Here, we use objective signal processing techniques and advanced statistical approaches to classify 616 calls recorded from semi‐free ranging animals. Based on four spectral and temporal acoustic parameters—quartile Q25, duration, spectral flux, and spectral flatness—extracted from a multivariate analysis, we refine and extend the conclusions drawn from previous work and present a statistically validated classification of the wild boar vocal repertoire into four call types: grunts, grunt‐squeals, squeals, and trumpets. While the majority of calls could be sorted into these categories using objective criteria, we also found evidence supporting a graded interpretation of some wild boar vocalizations as acoustically continuous, with the extremes representing discrete call types. The use of objective criteria based on modern techniques and statistics in respect to acoustic continuity advances our understanding of vocal variation. Integrating our findings with recent studies on domestic pig vocal behavior and emotions, we emphasize the importance of grunt‐squeals for acoustic approaches to animal welfare and underline the need of further research investigating the role of domestication on animal vocal communication.