{"title":"Introgression—Friend or Foe?","authors":"M. Hindrikson, E. Tammeleht","doi":"10.1111/mec.17810","DOIUrl":null,"url":null,"abstract":"<p>In this issue of Molecular Ecology, Sarabia et al. (<span>2025</span>), findings on potential adaptive introgression from dogs (Canis familiaris) into Iberian grey wolves (Canis lupus) present several fascinating and intriguing aspects. The study highlights a rare case of adaptive introgression, where genes from domestic dogs that were incorporated into the genome of Iberian grey wolves may have provided beneficial effects rather than deleterious ones. This challenges the common assumption that hybridization between wild species and domestic relatives primarily leads to negative outcomes. Six genes linked to immune response mechanisms and brain functions were found to carry alleles introgressed from dogs under positive selection in wild Iberian wolves, suggesting that the introgressed genes may help explain unique behavioural phenotypes observed in Iberian wolves (Figure 1), particularly their reduced dispersal compared to other wolf populations in Europe. Despite evidence for ancient gene flow between dogs and wolves over thousands of years, current study reports minimal recent hybridization events among contemporary Iberian wolf population (averaging around 0.6% recent dog ancestry). Understanding how adaptive traits could be introduced through introgression is vital for conservation efforts aimed at preserving genetic diversity within endangered species populations like the Iberian wolf.</p><p>Natural hybridization in the form of the interbreeding of two distinct taxa is a positive evolutionary force for introducing beneficial adaptive genetic variation into the genomic structure of species or populations Figure 1. The remarkable influence of hybridization and gene flow among canids in shaping phylogenetic relationships and population structures (Figure 2) underscores the potential significance of wolf-dog hybridization on existing grey wolf populations, particularly as wolves, being one of the most studied carnivore species with an abundance of ancient and modern genomes available, provide an excellent model for examining the effects of hybridization and introgression. Indeed, in Sarabia et al. (<span>2025</span>) recent availability of entire genomes of both wolves and domestic dogs has been put to use for the benefit of the current Iberian wolf population: 150 whole genomes of Iberian and other Eurasian grey wolves as well as dogs originating from across Europe were analysed to assess the extent and impact of dog introgression.</p><p>Hybridization between domesticated forms and their wild ancestors—anthropogenic hybridization—is mostly considered a threat to biodiversity, for example due to waste of reproductive effort of wild parental taxa. Wolf and dog, like all the other species in genus <i>Canis</i>, can interbreed and their fertile hybrids can backcross with both parental populations, leading to the introgression of domesticated genes into the wolf gene pool (Vilà and Wayne <span>1999</span>). Hybridization between wolves and dogs has been a recurrent phenomenon since the domestication of dogs (Pilot et al. <span>2021</span>), but it may be occurring at an accelerating rate in human-dominated landscapes, such as Europe. Large-scale surveys have confirmed ongoing and recent hybridization in several Eurasian wolf populations (e.g., Pilot et al. <span>2018</span>, <span>2021</span>; Salvatori et al. <span>2020</span>).</p><p>Recently, Santostasi et al. (<span>2025</span>) applied an individual-based model (IBM) to simulate the life cycle of wolves by projecting hybridization dynamics in a local wolf population and showed that lack of management led to complete admixture and genomic extinction. However, this may be true only in highly fragmented small wolf populations. For example, there seems to be no evidence of hybridization or introgression in the Scandinavian wolf population (Smeds et al. <span>2020</span>). Despite finding small blocks of dog ancestry in the genomes of 62% wolves sampled from all Eurasian populations analysed, the wolf populations have maintained a distinct genetic profile from dogs, suggesting that hybridization and backcrossing have occurred at a low frequency (Pilot et al. <span>2018</span>). By analysing 150 whole genomes from both Iberian and other Eurasian grey wolves, as well as dog populations across Europe and western Siberia, Sarabia et al. (<span>2025</span>) identified only about 5% ancient dog ancestry within the Iberian wolf population.</p><p>Introgression from domesticated species is generally believed to have predominantly negative impacts on wild populations, as genetic and phenotypic variations from domestication can be harmful to wild integrity, and the numerical dominance of domestic animals over their wild counterparts facilitates genetic swamping. The hybridization between wolves and dogs generally poses a conservation concern due to its potentially harmful long-term evolutionary effects, including the loss of adaptive gene combinations, unique genotypes with distinct evolutionary histories, and a reduction in fitness and adaptive potential due to the introduction of maladaptive traits (Smith et al. <span>2022</span>). However, the significant advancements in genetic tools over the past decades have enabled more detailed analyses and a deeper understanding of hybridization, introgression, and the genomic mechanisms underlying these processes. Sarabia et al. (<span>2025</span>) found some immune system gene variants from domestic animals to enhance the fitness of their wild relatives, besides genes influencing behavioural traits. Behavioural differences, such as decreased dispersal compared to other wolf populations, have previously been described in Iberian wolves. Moreover, examples from North American wolf populations show that one introgressed dog allele can increase individuals' fitness by conferring resistance to the canine distemper virus (Cubaynes et al. <span>2022</span>). Miao et al. (<span>2017</span>) results illustrate the opposite direction of positive introgression: the introgression of hypoxia adaptive genes in wolves from the highland played an important role for dogs living in hypoxic environments, indicating that domestic animals could acquire local adaptation quickly by secondary contact with their wild relatives.</p><p>As a conclusion, there is a new wave of evidence surfacing from the genomes of wolves that introgression may not be so frequent as previously thought and moreover, hybridization in itself may provide wolf populations a way of acquiring new adaptations to a rapidly changing environment. European legislation requires that wolf–dog hybridization is mitigated through effective management, mostly meaning killing the hybrid animals. However, Sarabia et al. (<span>2025</span>) study nicely underpins that eliminating individuals possessing dog-derived traits may prevent adaptations from being established in wolf populations and therefore we should, especially in Europe, where most wolf populations are presently large and expanding their range boundaries, let hybridization and furthermore, introgression, work their way.</p><p>The authors take full responsibility for his article.</p><p>The authors declare no conflicts of interest.</p>","PeriodicalId":210,"journal":{"name":"Molecular Ecology","volume":"34 12","pages":""},"PeriodicalIF":4.5000,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/mec.17810","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Molecular Ecology","FirstCategoryId":"99","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/mec.17810","RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"BIOCHEMISTRY & MOLECULAR BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
In this issue of Molecular Ecology, Sarabia et al. (2025), findings on potential adaptive introgression from dogs (Canis familiaris) into Iberian grey wolves (Canis lupus) present several fascinating and intriguing aspects. The study highlights a rare case of adaptive introgression, where genes from domestic dogs that were incorporated into the genome of Iberian grey wolves may have provided beneficial effects rather than deleterious ones. This challenges the common assumption that hybridization between wild species and domestic relatives primarily leads to negative outcomes. Six genes linked to immune response mechanisms and brain functions were found to carry alleles introgressed from dogs under positive selection in wild Iberian wolves, suggesting that the introgressed genes may help explain unique behavioural phenotypes observed in Iberian wolves (Figure 1), particularly their reduced dispersal compared to other wolf populations in Europe. Despite evidence for ancient gene flow between dogs and wolves over thousands of years, current study reports minimal recent hybridization events among contemporary Iberian wolf population (averaging around 0.6% recent dog ancestry). Understanding how adaptive traits could be introduced through introgression is vital for conservation efforts aimed at preserving genetic diversity within endangered species populations like the Iberian wolf.
Natural hybridization in the form of the interbreeding of two distinct taxa is a positive evolutionary force for introducing beneficial adaptive genetic variation into the genomic structure of species or populations Figure 1. The remarkable influence of hybridization and gene flow among canids in shaping phylogenetic relationships and population structures (Figure 2) underscores the potential significance of wolf-dog hybridization on existing grey wolf populations, particularly as wolves, being one of the most studied carnivore species with an abundance of ancient and modern genomes available, provide an excellent model for examining the effects of hybridization and introgression. Indeed, in Sarabia et al. (2025) recent availability of entire genomes of both wolves and domestic dogs has been put to use for the benefit of the current Iberian wolf population: 150 whole genomes of Iberian and other Eurasian grey wolves as well as dogs originating from across Europe were analysed to assess the extent and impact of dog introgression.
Hybridization between domesticated forms and their wild ancestors—anthropogenic hybridization—is mostly considered a threat to biodiversity, for example due to waste of reproductive effort of wild parental taxa. Wolf and dog, like all the other species in genus Canis, can interbreed and their fertile hybrids can backcross with both parental populations, leading to the introgression of domesticated genes into the wolf gene pool (Vilà and Wayne 1999). Hybridization between wolves and dogs has been a recurrent phenomenon since the domestication of dogs (Pilot et al. 2021), but it may be occurring at an accelerating rate in human-dominated landscapes, such as Europe. Large-scale surveys have confirmed ongoing and recent hybridization in several Eurasian wolf populations (e.g., Pilot et al. 2018, 2021; Salvatori et al. 2020).
Recently, Santostasi et al. (2025) applied an individual-based model (IBM) to simulate the life cycle of wolves by projecting hybridization dynamics in a local wolf population and showed that lack of management led to complete admixture and genomic extinction. However, this may be true only in highly fragmented small wolf populations. For example, there seems to be no evidence of hybridization or introgression in the Scandinavian wolf population (Smeds et al. 2020). Despite finding small blocks of dog ancestry in the genomes of 62% wolves sampled from all Eurasian populations analysed, the wolf populations have maintained a distinct genetic profile from dogs, suggesting that hybridization and backcrossing have occurred at a low frequency (Pilot et al. 2018). By analysing 150 whole genomes from both Iberian and other Eurasian grey wolves, as well as dog populations across Europe and western Siberia, Sarabia et al. (2025) identified only about 5% ancient dog ancestry within the Iberian wolf population.
Introgression from domesticated species is generally believed to have predominantly negative impacts on wild populations, as genetic and phenotypic variations from domestication can be harmful to wild integrity, and the numerical dominance of domestic animals over their wild counterparts facilitates genetic swamping. The hybridization between wolves and dogs generally poses a conservation concern due to its potentially harmful long-term evolutionary effects, including the loss of adaptive gene combinations, unique genotypes with distinct evolutionary histories, and a reduction in fitness and adaptive potential due to the introduction of maladaptive traits (Smith et al. 2022). However, the significant advancements in genetic tools over the past decades have enabled more detailed analyses and a deeper understanding of hybridization, introgression, and the genomic mechanisms underlying these processes. Sarabia et al. (2025) found some immune system gene variants from domestic animals to enhance the fitness of their wild relatives, besides genes influencing behavioural traits. Behavioural differences, such as decreased dispersal compared to other wolf populations, have previously been described in Iberian wolves. Moreover, examples from North American wolf populations show that one introgressed dog allele can increase individuals' fitness by conferring resistance to the canine distemper virus (Cubaynes et al. 2022). Miao et al. (2017) results illustrate the opposite direction of positive introgression: the introgression of hypoxia adaptive genes in wolves from the highland played an important role for dogs living in hypoxic environments, indicating that domestic animals could acquire local adaptation quickly by secondary contact with their wild relatives.
As a conclusion, there is a new wave of evidence surfacing from the genomes of wolves that introgression may not be so frequent as previously thought and moreover, hybridization in itself may provide wolf populations a way of acquiring new adaptations to a rapidly changing environment. European legislation requires that wolf–dog hybridization is mitigated through effective management, mostly meaning killing the hybrid animals. However, Sarabia et al. (2025) study nicely underpins that eliminating individuals possessing dog-derived traits may prevent adaptations from being established in wolf populations and therefore we should, especially in Europe, where most wolf populations are presently large and expanding their range boundaries, let hybridization and furthermore, introgression, work their way.
The authors take full responsibility for his article.
在本期的《分子生态学》中,Sarabia等人(2025)研究了犬类(Canis familiaris)对伊比利亚灰狼(Canis lupus)的潜在适应性渗入,提出了几个令人着迷和有趣的方面。这项研究强调了一个罕见的适应性基因渗入的案例,即来自家养狗的基因被整合到伊比利亚灰狼的基因组中,可能产生了有益的影响,而不是有害的影响。这挑战了野生物种和家养亲缘种杂交主要导致负面结果的普遍假设。研究发现,在野生伊比利亚狼中,6个与免疫反应机制和脑功能相关的基因在正选择下携带来自狗的等位基因渐渗,这表明渐渗基因可能有助于解释在伊比利亚狼中观察到的独特行为表型(图1),特别是与欧洲其他狼种群相比,它们的扩散减少了。尽管有证据表明数千年前狗和狼之间存在古老的基因流动,但目前的研究表明,在当代伊比利亚狼种群中,最近的杂交事件很少(平均约为0.6%)。了解适应性性状是如何通过基因渗入引入的,对于保护伊比利亚狼等濒危物种种群的遗传多样性至关重要。以两个不同分类群的杂交为形式的自然杂交是一种积极的进化力量,可以将有益的适应性遗传变异引入物种或群体的基因组结构中(图1)。犬科动物之间的杂交和基因流动在形成系统发育关系和种群结构方面的显著影响(图2)强调了狼狗杂交对现有灰狼种群的潜在意义,特别是狼作为研究最多的食肉动物物种之一,拥有丰富的古代和现代基因组,为研究杂交和基因渗入的影响提供了一个很好的模型。事实上,在Sarabia等人(2025)的研究中,狼和家犬的全基因组已被用于当前的伊比利亚狼种群:分析了150个伊比利亚和其他欧亚灰狼以及来自欧洲各地的狗的全基因组,以评估狗的入侵程度和影响。驯化形式与野生祖先之间的杂交——人为杂交——大多被认为是对生物多样性的威胁,例如由于野生亲本分类群繁殖努力的浪费。狼和狗,像所有犬属的其他物种一样,可以杂交,它们的可育杂种可以与亲本种群回交,导致驯化基因渗入狼的基因库(vil<e:1>和韦恩1999)。自狗被驯化以来,狼和狗之间的杂交一直是一种反复出现的现象(Pilot et al. 2021),但在人类主导的地区(如欧洲),这种现象可能正在加速发生。大规模调查证实了几个欧亚狼种群正在进行和最近的杂交(例如,Pilot等人。2018年,2021年;Salvatori et al. 2020)。最近,Santostasi等人(2025)应用基于个体的模型(IBM)通过预测当地狼种群的杂交动态来模拟狼的生命周期,并表明缺乏管理导致完全混合和基因组灭绝。然而,这可能只在高度分散的小狼种群中是正确的。例如,在斯堪的纳维亚狼种群中似乎没有杂交或渐渗的证据(Smeds et al. 2020)。尽管在分析的所有欧亚种群样本中,62%的狼的基因组中发现了一小块狗的祖先,但狼种群保持了与狗不同的遗传特征,这表明杂交和回交发生的频率很低(Pilot等人,2018)。通过分析来自伊比利亚灰狼和其他欧亚灰狼以及欧洲和西伯利亚西部的狗种群的150个全基因组,Sarabia等人(2025)在伊比利亚狼种群中仅确定了约5%的古代狗祖先。驯化物种的渗入通常被认为对野生种群有主要的负面影响,因为驯化产生的遗传和表型变异可能对野生种群的完整性有害,而且家畜相对于野生动物的数量优势促进了遗传沼泽。狼和狗之间的杂交通常会引起保护问题,因为其潜在的有害的长期进化影响,包括适应性基因组合的丧失,具有不同进化历史的独特基因型,以及由于引入适应不良性状而导致的适应性和适应潜力的降低(Smith et al. 2022)。 然而,在过去的几十年里,遗传工具的重大进步使得对杂交、基因渗入和这些过程背后的基因组机制有了更详细的分析和更深入的了解。Sarabia et al.(2025)除了发现影响行为特征的基因外,还从家畜身上发现了一些免疫系统基因变异,以增强其野生亲缘动物的适应性。与其他狼种群相比,伊比利亚狼的行为差异,如分散减少,此前已在伊比利亚狼中得到描述。此外,来自北美狼种群的例子表明,一个渗入的狗等位基因可以通过赋予对犬瘟热病毒的抵抗力来提高个体的适应性(Cubaynes et al. 2022)。Miao等人(2017)的研究结果说明了正渗的相反方向:高原狼的低氧适应基因的渗渗对生活在低氧环境中的狗发挥了重要作用,这表明家畜可以通过与野生亲属的二次接触快速获得当地适应。综上所述,来自狼基因组的新一波证据表明,基因渗入可能并不像以前认为的那样频繁,而且,杂交本身可能为狼种群提供了一种获得新的适应快速变化的环境的方式。欧洲立法要求通过有效的管理来减少狼狗杂交,这主要意味着杀死杂交动物。然而,Sarabia等人(2025)的研究很好地支持了消除具有狗衍生特征的个体可能会阻止狼种群中的适应性建立,因此我们应该,特别是在欧洲,大多数狼种群目前很大,并且正在扩大其范围边界,让杂交和进一步的渗入发挥作用。作者对他的文章负全部责任。作者声明无利益冲突。
期刊介绍:
Molecular Ecology publishes papers that utilize molecular genetic techniques to address consequential questions in ecology, evolution, behaviour and conservation. Studies may employ neutral markers for inference about ecological and evolutionary processes or examine ecologically important genes and their products directly. We discourage papers that are primarily descriptive and are relevant only to the taxon being studied. Papers reporting on molecular marker development, molecular diagnostics, barcoding, or DNA taxonomy, or technical methods should be re-directed to our sister journal, Molecular Ecology Resources. Likewise, papers with a strongly applied focus should be submitted to Evolutionary Applications. Research areas of interest to Molecular Ecology include:
* population structure and phylogeography
* reproductive strategies
* relatedness and kin selection
* sex allocation
* population genetic theory
* analytical methods development
* conservation genetics
* speciation genetics
* microbial biodiversity
* evolutionary dynamics of QTLs
* ecological interactions
* molecular adaptation and environmental genomics
* impact of genetically modified organisms