Investigating temporal changes in hybridization and introgression in a predominantly bimodal hybridizing population of invasive sika (Cervus nippon) and native red deer (C. elaphus) on the Kintyre Peninsula,Scotland

We investigated temporal changes in hybridization and introgression between native red deer (Cervus elaphus) and invasive Japanese sika (Cervus nippon) on the Kintyre Peninsula, Scotland, over 15 years, through analysis of 1513 samples of deer at 20 microsatellite loci and a mtDNA marker. We found no evidence that either the proportion of recent hybrids, or the levels of introgression had changed over the study period. Nevertheless, in one population where the two species have been in contact since ～1970, 44% of individuals sampled during the study were hybrids. This suggests that hybridization between these species can proceed fairly rapidly. By analysing the number of alleles that have introgressed from polymorphic red deer into the genetically homogenous sika population, we reconstructed the haplotypes of red deer alleles introduced by backcrossing. Five separate hybridization events could account for all the recently hybridized sika‐like individuals found across a large section of the Peninsula. Although we demonstrate that low rates of F1 hybridization can lead to substantial introgression, the progress of hybridization and introgression appears to be unpredictable over the short timescales.     

Introgression of exotic Cervus (nippon and canadensis) into red deer (Cervus elaphus) populations in Scotland and the English Lake District

Since the mid‐19th century, multiple introductions of Japanese sika deer (Cervus nippon nippon) and North American wapiti (C. canadensis) have taken place in the British Isles. While wapiti have generally been unsuccessful, sika have been very successful, especially in Scotland where they now overlap at least 40% of the range of native red deer (C. elaphus). Hybridization between these two species and red deer has been demonstrated in captivity and in the wild. Using a panel of 22 microsatellite loci that are highly diagnostic between red deer and sika, and moderately diagnostic between red deer and wapiti, we investigated the extent of introgression between these species in 2,943 deer sampled from around Scotland and from the English Lake District using the Bayesian clustering software STRUCTURE. We also used a diagnostic mitochondrial marker for red deer and sika. Our survey extends previous studies indicating little introgression of wapiti nuclear alleles into red deer, in particular in Northern Scotland, Kintyre, and the Lake District. We found a new area of extensive sika introgression in South Kintyre. In the North Highlands, we show for the first time geographically scattered evidence of past hybridization followed by extensive backcrossing, including one red‐like individual with sika introgression, two sika‐like individuals with red deer introgression, and six individuals that were apparently pure sika at the nuclear markers assessed but which carried red deer mitochondria. However, there has not been a collapse of assortative mating in this region. Similarly, in the English Lake District red deer, we found only traces of past sika introgression. No sika alleles were detected in the Central Highlands or the Hebridean red deer refugia. We make suggestions for management to prevent further spread of sika alleles into red deer and vice versa.     

Female Sexual Preferences Toward Conspecific and Hybrid Male Mating Calls in Two Species of Polygynous Deer, <Emphasis Type="Italic">Cervus elaphu</Emphasis>s and <Emphasis Type="Italic">C. nippon</Emphasis>

The behavioral processes at the basis of hybridization and introgression are understudied in terrestrial mammals. We use a unique model to test the role of sexual signals as a reproductive barrier to introgression by investigating behavioral responses to male sexual calls in estrous females of two naturally allopatric but reproductively compatible deer species, red deer and sika deer. Previous studies demonstrated asymmetries in acoustic species discrimination between these species: most but not all female red deer prefer conspecific over sika deer male calls while female sika deer exhibit no preference differences. Here, we extend this examination of acoustic species discrimination to the role of male sexual calls in introgression between parent species and hybrids. Using two-speaker playback experiments, we compared the preference responses of estrous female red and sika deer to male sexual calls from conspecifics versus red × sika hybrids. These playbacks simulate early secondary contact between previously allopatric species after hybridization has occurred. Based on previous conspecific versus heterospecific playbacks, we predicted that most female red deer would prefer conspecific calls while female sika deer would show no difference in their preference behaviors toward conspecific and hybrid calls. However, results show that previous asymmetries did not persist as neither species exhibited more preferences for conspecific over hybrid calls. Thus, vocal behavior is not likely to deter introgression between these species during the early stages of sympatry. On a wider scale, weak discrimination against hybrid sexual signals could substantially contribute to this important evolutionary process in mammals and other taxa.     

Evaluation of introgressive hybridization among Cervidae in Japan's Kinki District via two novel genetic markers developed from public NGS data

Hybridization and backcrossing of native populations with introduced species can lead to introgression and genetic alteration. In this study, we evaluated introgression in 43 deer from a potential hybrid zone around Okinoshima Island, Kinki District, Japan. This region witnessed the migration of a hybrid population (cross between the Formosan sika deer [Cervus nippon taiouanus] and other deer species) that could potentially breed with the native Japanese sika deer (C. n. centralis). We used an existing genetic marker for the mitochondrial cytochrome b gene and two novel markers for nuclear DNA, developed using publicly available next‐generation sequencing data. We identified one mainland deer with a mitochondrial haplotype identical to that of the Formosan sika deer as well as nuclear heterozygous sequences identical to those of Formosan and Japanese sika deer. This suggests that the mainland deer is a hybrid offspring of the Okinoshima population and native deer. However, only Japanese sika deer sequences were found in the other 42 samples, indicating limited introgression. Nevertheless, hybridization pre‐ and postintroduction in the Okinoshima population could cause multispecies introgression among Japanese sika deer, negatively affecting genetic integrity. We developed a simple test based on polymerase chain reaction–restriction fragment length polymorphism to detect introgression in natural populations. Our method can accelerate genetic monitoring of Japanese sika deer in Kinki District. In conclusion, to prevent further introgression and maintain genetic integrity of Japanese sika deer, we recommend establishing fences around Okinoshima Island to limit migration, besides a continued genetic monitoring of the native deer.     

A genetic study of sika (Cervus nippon) in the New Forest and in the Purbeck region, southern England: is there evidence of recent or past hybridization with red deer (Cervus elaphus)?

Sika Cervus nippon are native to Japan and East Asia but are now naturalized in many parks of the world, including Britain. In contrast to the substantial body of research on the extent of hybridization between sika and red deer Cervus elaphus in Scottish populations, there has been little genetic analysis of the English populations of sika. Sika in England still have a patchy and discontinuous distribution; populations are thus still genetically isolated and may be expected to show higher variability in genetic type. The current paper uses DNA-based techniques to explore the genetic composition of sika in the New Forest (Hampshire) and that of sika from the largest population in England, in the Purbeck region (Dorset). The study aims were to determine whether New Forest sika show signs of recent interbreeding with New Forest red deer populations, whether New Forest sika are genetically distinct from Purbeck sika, and whether New Forest and Purbeck sika show evidence of past hybridization or whether they are pure (non-hybrid) strains. Microsatellite analysis was used to compare the genetic profiles of individual deer. Results showed that sika and red deer in the New Forest were genetically distinct, indicating that there is no large-scale in situ hybridization occurring between these feral populations. In terms of overall genetic composition, there was no significant difference between the sika in the New Forest and Purbeck. However, a more detailed analysis found that New Forest sika showed a lower level of introgression with red deer compared with the Purbeck sika. We conclude that, overall, the New Forest sika deer do appear to be more genetically pure bred than the Purbeck sika.     

The establishment of a hybrid zone between red and sika deer (genus Cervus)

Japanese sika deer ( Cervus nippon nippon ) were introduced to Scotland around 80 years (20 generations) ago. The sika phenotype is expanding its range and hybridizing extensively with native red deer ( Cervus elaphus ) leading to the establishment of a hybrid zone. This zone is currently moving and cannot be considered to be at equilibrium. Cervid genotypes and mitochondrial haplotypes were mapped across the sika phenotype range, using diagnostic protein isozymes, microsatellite nuclear DNA markers and RFLPs in mtDNA. These were analysed to estimate heterozygote deficits and nuclear linkage disequilibria and cytonuclear disequilibria in relation to gene frequencies and time since contact. Introgression was found in both taxa and strong linkage disequilibria and heterozygote deficits characterize the populations longest exposed to hybridization. Populations further from the introduction site, where hybridization is facilitated by the dispersal of sika-like stags, show low values for linkage disequilibria and heterozygote deficit. The observed patterns in genotype are explained in terms of assortative mating and a selective advantage of the sika genotype. The genetic integrity of the Scottish mainland red deer is shown to be at risk from the invasion of sika.     

Introgression through rare hybridization: A genetic study of a hybrid zone between red and sika deer (genus Cervus) in Argyll, Scotland

In this article we describe the structure of a hybrid zone in Argyll, Scotland, between native red deer (Cervus elaphus) and introduced Japanese sika deer (Cervus nippon), on the basis of a genetic analysis using 11 microsatellite markers and mitochondrial DNA. In contrast to the findings of a previous study of the same population, we conclude that the deer fall into two distinct genetic classes, corresponding to either a sika-like or red-like phenotype. Introgression is rare at any one locus, but where the taxa overlap up to 40% of deer carry apparently introgressed alleles. While most putative hybrids are heterozygous at only one locus, there are rare multiple heterozygotes, reflecting significant linkage disequilibrium within both sika- and red-like populations. The rate of backcrossing into the sika population is estimated as H = 0.002 per generation and into red, H = 0.001 per generation. On the basis of historical evidence that red deer entered Kintyre only recently, a diffusion model evaluated by maximum likelihood shows that sika have increased at approximately 9.2% yr-1 from low frequency and disperse at a rate of approximately 3.7 km yr-1. Introgression into the red-like population is greater in the south, while introgression into sika varies little along the transect. For both sika- and red-like populations, the degree of introgression is 30-40% of that predicted from the rates of current hybridization inferred from linkage disequilibria; however, in neither case is this statistically significant evidence for selection against introgression.     

Genetic structure of,and hybridisation between,red (Cervus elaphus) and sika (Cervus nippon) deer in Ireland

This study investigated the levels of genetic diversity and variation exhibited by red and sika deer in Ireland, along with the extent and regional location of hybridisation between these two species. Bi-parental (microsatellites) and maternally-inherited (mitochondrial DNA) genetic markers were utilised that allowed comparisons between 85 red deer from six localities and 47 sika deer from 3 localities in Ireland. Population genetic structure was assessed using Bayesian analysis, indicating the existence of two genetic clusters in sika deer and three clusters in red deer. Levels of genetic diversity were low in both red and sika deer. These genetic data presented herein indicate a recent introduction of sika deer and subsequent translocations in agreement with historical data. The origins of the current red deer populations found in Ireland, based on genetic data presented in this study, still remain obscure. All hybrid deer (red/sika) found in this study were found in Wicklow, Galway and Mayo where the ‘red-like’ deer exhibited sika deer alleles/haplotypes, and vice versa in the case of Wicklow. Molecular methods proved invaluable in the identification of the hybrid deer because identification of hybrids based on phenotypic external appearances (pelage and body proportions) can be misleading. Areas where red and sika deer are sympatric need to be assessed for the level and extent of hybridisation occurring and thus need to be managed in order to protect the genetic integrity of ‘pure’ red deer populations.     

Comparative rumen morphology of sympatric sika deer (Cervus nippon) and red deer (C. elaphus scoticus) in the Ahimanawa and Kaweka Ranges,central North Island,New Zealand

Eighteen sika deer (Cervus nippon) and 14 red deer (C. elaphus scoticus) were sampled from two areas where these closely related species are sympatric. Total body weight, carcass weight, age class, sex, and internal parameters (e.g. liver weight, kidney weight, rumen volume) were recorded. Samples of rumen wall mucosa taken from the dorsal rumen wall, atrium ruminis, caudoventral blindsac, and ventral rumen wall were used to compare rumen morphology between the two species (and also any area, sex, and age effects). Sika deer had significantly lower papilla densities in three of the four rumen wall sites and significantly smaller papillae than red deer in two of the four sites. Surface enlargement factors (SEFs) were calculated to provide comparisons of the effective absorptive surface within the rumens of the two species. The mean SEF for sika deer (4.76) was significantly less that for red deer (6.77), which suggests a greater degree of adaptation to digesting fibrous forage. In the central North Island, New Zealand, where the habitat has been considerably modified by introduced herbivores over the last century and food resources are depleted, such an adaptation would confer a competitive advantage on sika deer over red deer. It is postulated that this diet-related difference largely accounts for the ongoing replacement of red deer by sika deer where these two species are sympatric.     

A survey of the hybridisation status of Cervus deer species on the island of Ireland

Red deer (Cervus elaphus) did not recolonise Ireland after the last glaciation, but the population in Co. Kerry is descended from an ancient (c. 5000 BP) introduction and merits conservation. During the mid-19th century exotic species including North American wapiti (C. canadensis) and Japanese sika deer (C. nippon nippon) were introduced to Ireland, mainly via Powerscourt Park, Co. Wicklow. While wapiti failed to establish, sika thrived, dispersed within Co. Wicklow and were translocated to other sites throughout Ireland. Red deer and sika are known to have hybridised in Ireland, particularly in Co. Wicklow, but an extensive survey with a large, highly diagnostic marker panel is required to assess the threat hybridisation potentially poses to the Co. Kerry red deer population. Here, 374 individuals were genotyped at a panel of 22 microsatellites and at a single mtDNA marker that are highly diagnostic for red deer and Japanese sika. The microsatellites are also moderately diagnostic for red deer and wapiti. Wapiti introgression was very low [trace evidence in 2 (0.53 %) individuals]. Despite long-standing sympatry of red deer and sika in the area, no red deer-sika hybrids were detected in Co. Kerry suggesting strong assortative mating by both species in this area. However, 80/197 (41 %) of deer sampled in Co. Wicklow and 7/15 (47 %) of deer sampled in Co. Cork were red-sika hybrids. Given their proximity and that hybrids are less likely to mate assortatively than pure individuals, the Co. Cork hybrids pose a threat to the Co. Kerry red deer.     

Suppression of Regeneration in New Zealand Mountain Beech Forests is Dependent on Species of Introduced Deer

We compared the impacts on forest regeneration of introduced sika (Cervus nippon) and red (Cervus elaphus) deer in New Zealand. Plot data were used to compare mountain beech (Nothofagus solandri var. cliffortioides) regeneration between a region with sika deer, and four regions without sika deer. All regions surveyed had red deer present. In the region where sika deer had been present for more than a decade, there was evidence of poor mountain beech seedling regeneration. In the four regions without sika deer, there was evidence of a strong regenerative response at stands with low occupancy by trees. When compared to larger deer species, sika deer have a digestive morphology allowing greater dietary versatility, which may result in them impeding forest regeneration where red deer do not. In contrast to mountain beech, some small-leaved shrub species may have been competitively advantaged by intensive browsing from sika deer. This is contra to a current view that small-leaved shrub species with interlacing branches were able to tolerate browsing from extinct ratite birds, but not introduced deer. Sika deer have been introduced into countries where other deer species are indigenous, such as Canada, Denmark, Great Britain, Czech Republic, Ireland and the United States of America. Because of their dietary advantage, sika deer may have a greater potential to impede forest regeneration and competitively exclude larger deer species, particularly at low basal area sites where impacts on tree regeneration are likely to be greatest.     

四川梅花鹿春季昼夜活动节律与时间分配

1997年4月,在四川铁布自然保护区用直接观察法对220头次四川梅花鹿群的昼夜活动节律和时间分配进行了观察。结果表明,鹿群春季昼夜活动的规律性较强。白昼,鹿群活动呈现明显的双峰型,2个高峰时段为08：30和19：30前后,活动频率分别为71．9％和94．13％,其他时间多处于休息状态;鹿群夜间活动强于昼间,活动频率均在6l％以上,仅在半夜01：30前后有一个相对不活跃期。同时发现,春季活动高峰期约90％的活动时间被四川梅花鹿用于采食和移动。这可能与光照、食物及人类活动的影响有关。     

Landscape features affect gene flow of Scottish Highland red deer (Cervus elaphus)

Landscape features have been shown to strongly influence dispersal and, consequently, the genetic population structure of organisms. Studies quantifying the effect of landscape features on gene flow of large mammals with high dispersal capabilities are rare and have mainly been focused at large geographical scales. In this study, we assessed the influence of several natural and human-made landscape features on red deer gene flow in the Scottish Highlands by analysing 695 individuals for 21 microsatellite markers. Despite the relatively small scale of the study area (115 × 87 km), significant population structure was found using F -statistics ( F _ST = 0.019) and the program structure , with major differentiation found between populations sampled on either side of the main geographical barrier (the Great Glen). To assess the effect of landscape features on red deer population structure, the ArcMap GIS was used to create cost-distance matrices for moving between populations, using a range of cost values for each of the landscape features under consideration. Landscape features were shown to significantly affect red deer gene flow as they explained a greater proportion of the genetic variation than the geographical distance between populations. Sea lochs were found to be the most important red deer gene flow barriers in our study area, followed by mountain slopes, roads and forests. Inland lochs and rivers were identified as landscape features that might facilitate gene flow of red deer. Additionally, we explored the effect of choosing arbitrary cell cost values to construct least cost-distance matrices and described a method for improving the selection of cell cost values for a particular landscape feature.     

Hybrid swarm between divergent lineages of mule deer (Odocoileus hemionus)

Studies of hybrid zones have revealed an array of evolutionary outcomes, yet the underlying structure is typically characterized as one of three types: a hybrid zone, a hybrid swarm or a hybrid taxon. Our primary objective was to determine which of these three structures best characterizes a zone of hybridization between two divergent lineages of mule deer (Odocoileus hemionus), mule deer and black-tailed deer. These lineages are morphologically, ecologically and genetically distinct, yet hybridize readily along a zone of secondary contact between the east and west slopes of the Cascade Mountains (Washington and Oregon, USA). Using microsatellite and mitochondrial DNA, we found clear evidence for extensive hybridization and introgression between lineages, with varying degrees of admixture across the zone of contact. The pattern of hybridization in this region closely resembles a hybrid swarm; based on data from 10 microsatellite loci, we detected hybrids that extend well beyond the F1 generation, did not detect linkage disequilibrium at the centre of the zone and found that genotypes were associated randomly within the zone of contact. Introgression was characterized as bidirectional and symmetric, which is surprising given that the zone of contact occurs along a sharp ecotone and that lineages are characterized by large differences in body size (a key component of mating success). Regardless of the underlying mechanisms promoting hybrid swarm maintenance, it is clear that the persistence of a hybrid swarm presents unique challenges for management in this region.     

Genetic diversity and demographic history of introduced sika deer on the Delmarva Peninsula

The introduction of non‐native species can have long‐term effects on native plant and animal communities. Introduced populations are occasionally not well understood and offer opportunities to evaluate changes in genetic structure through time and major population changes such as bottleneck and or founder events. Invasive species can often evolve rapidly in new and novel environments, which could be essential to their long‐term success. Sika deer are native to East Asia, and their introduction and establishment to the Delmarva Peninsula, USA, is poorly documented, but probably involved ≥1 founder and/or bottleneck events. We quantified neutral genetic diversity in the introduced population and compared genetic differentiation and diversity to the presumed source population from Yakushima Island, Japan, and a captive population of sika deer in Harrington, Delaware, USA. Based on the data from 10 microsatellite DNA loci, we observed reduced genetic variation attributable to founder events, support for historic hybridization events, and evidence that the population did originate from Yakushima Island stocks. Estimates of population structure through Bayesian clustering and demographic history derived from approximate Bayesian computation (ABC), were consistent with the hypothesized founder history of the introduced population in both timing and effective population size (approximately five effective breeding individuals, an estimated 36 generations ago). Our ABC results further supported a single introduction into the wild happening before sika deer spread throughout the Delmarva. We conclude that free‐ranging sika deer on Delmarva are descended from ca. five individuals introduced about 100 years ago from captive stocks of deer maintained in the United Kingdom. Free‐ranging sika deer on Delmarva have lost neutral diversity due to founder and bottleneck events, yet populations have expanded in recent decades and show no evidence of abnormalities associated with inbreeding. We suggest management practices including increasing harvest areas and specifically managing sika deer outside of Maryland.     

Convergent evolutionary processes driven by foraging opportunity in two sympatric morph pairs of Arctic charr with contrasting post‐glacial origins

The expression of two or more discrete phenotypes amongst individuals within a species (morphs) provides multiple modes upon which selection can act semi‐independently, and thus may be an important stage in speciation. In the present study, we compared two sympatric morph systems aiming to address hypotheses related to their evolutionary origin. Arctic charr in sympatry in Loch Tay, Scotland, exhibit one of two discrete, alternative body size phenotypes at maturity (large or small body size). Arctic charr in Loch Awe segregate into two temporally segregated spawning groups (breeding in either spring or autumn). Mitochondrial DNA restriction fragment length polymorphism analysis showed that the morph pairs in both lakes comprise separate gene pools, although segregation of the Loch Awe morphs is more subtle than that of Loch Tay. We conclude that the Loch Awe morphs diverged in situ (within the lake), whereas Loch Tay morphs most likely arose through multiple invasions by different ancestral groups that segregated before post‐glacial invasion (i.e. in allopatry). Both morph pairs showed clear trophic segregation between planktonic and benthic resources (measured by stable isotope analysis) but this was significantly less distinct in Loch Tay than in Loch Awe. By contrast, both inter‐morph morphological and life‐history differences were more subtle in Loch Awe than in Loch Tay. The strong ecological but relatively weak morphological and life‐history divergence of the in situ derived morphs compared to morphs with allopatric origins indicates a strong link between early ecological and subsequent genetic divergence of sympatric origin emerging species pairs. The emergence of parallel specialisms despite distinct genetic origins of these morph pairs suggests that the effect of available foraging opportunities may be at least as important as genetic origin in structuring sympatric divergence in post‐glacial fishes with high levels of phenotypic plasticity. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Bayesian analysis of hybridization and introgression between the endangered european mink (Mustela lutreola) and the polecat (Mustela putorius)

Human-mediated global change will probably increase the rates of natural hybridization and genetic introgression between closely related species, and this will have major implications for conservation of the taxa involved. In this study, we analyse both mitochondrial and nuclear data to characterize ongoing hybridization and genetic introgression between two sympatric sister species of mustelids, the endangered European mink (Mustela lutreola) and the more abundant polecat (M. putorius). A total of 317 European mink, 114 polecats and 15 putative hybrid individuals were collected from different localities in Europe and genotyped with 13 microsatellite nuclear markers. Recently developed Bayesian methods for assigning individuals to populations and identifying admixture proportions were applied to the genetic data. To identify the direction of hybridization, we additionally sequenced mtDNA and Y chromosomes from 78 individuals and 29 males respectively. We found that both hybridization and genetic introgression occurred at low levels (3% and 0.9% respectively) and indicated that hybridization is asymmetric, as only pure polecat males mate with pure European mink females. Furthermore, backcrossing and genetic introgression was detected only from female first-generation (F1) hybrids of European mink to polecats. This latter result implies that Haldane's rule may apply. Our results suggest that hybridization and genetic introgression between the two species should be considered a rather uncommon event. However, the current low densities of European mink might be changing this trend.     

Tracing the genetic roots of the sika deer Cervus nippon naturalized in Germany and Austria

To determine the geographical origin of the sika deer (Cervus nippon) naturalized in Germany and Austria, we sequenced the mitochondrial control region for 214 individuals. Adding these sequences to previously published data from native sika deer across its natural geographic range, the total comes to 245, extending what is already known about the geographical variation in this sequence in Cervus nippon. From these sequences, a neighbour-joining tree was constructed. This tree showed that the 49 different mitochondrial (mt)DNA types are grouped into three distinct phylogenetic clusters, which correspond to different geographic areas. Similarities between sequences of the naturalized sika deer and those described from native sika deer from both southern Honshu, Kyushu with associated islands, and northern Honshu suggest that the ancestors of the sika deer populations in Germany and Austria originated from the Japanese archipelago. In contrast, there is no evidence that female sika deer of Chinese, Taiwanese or north Vietnamese origin were involved in the ancestry of the present sika population in Germany and Austria.     

中国大陆梅花鹿mtDNA控制区序列变异及种群遗传结构分析

测定了37只中国大陆梅花鹿(Cervus nippon)不同种群mtDNA控制区5′端351 bp的序列，共发现23个变异位点，定义了5种单元型。分子变异分析表明，中国大陆梅花鹿出现了显著的种群分化(Φm＝0．45，Fst＝0．60，P＜0．001)，支持把分布于东北、华南和四川的梅花鹿种群归入各自独立的管理单元。中国大陆、日本南部和日本北部之间无共享单元型，且有25个鉴别位点。最小跨度网络图(Minimum spannlng network，MSN)和基于最大似然法和邻接法的系统发生分析均把单元型聚类为对应于中国大陆、日本南部和日本北部的三个单系，其中中国大陆和日本南部梅花鹿有相对较近的亲缘关系，支持日本梅花鹿的祖先通过至少两个大陆桥从亚洲迁移到日本的观点。     

Distribution and range expansion of deer in Ireland

• 1 Throughout Europe, the range of many deer species is expanding. We provide current distribution maps for red deer Cervus elaphus, sika Cervus nippon, fallow deer Dama dama and muntjac deer Muntiacus sp. in Ireland, and estimates of range expansion rates for red deer, sika and fallow deer.
• 2 There was a considerable expansion in the ranges of red deer, sika and fallow deer between 1978 and 2008. The compound annual rate of expansion was 7% for red deer, 5% for sika and 3% for fallow deer. The total range increase was 565% for red deer, 353% for sika and 174% for fallow deer. The potential implications of these expansions are discussed.
• 3 There are unknown numbers of red‐sika hybrid deer in some parts of Ireland. Range expansion is likely to lead to further hybridizations with implications for the genetic integrity of deer stocks.
• 4 Sightings of free‐roaming muntjac deer were first recorded in 2007. The distribution of confirmed sightings of single and multiple animals in the eastern region of Ireland suggests multiple releases.
• 5 Deer are already impacting on both the economic and biodiversity values of habitats in Ireland, where, at present, no sustainable deer management policy exists.