Introgression Research Articles

Mito-nuclear discordance within Anthozoa, with notes on unique properties of their mitochondrial genomes

Whole mitochondrial genomes are often used in phylogenetic reconstruction. However, discordant patterns in species relationships between mitochondrial and nuclear phylogenies are commonly observed. Within Anthozoa (Phylum Cnidaria), mitochondrial (mt)-nuclear discordance has not yet been examined using a large and comparable dataset. Here, we used data obtained from target-capture enrichment sequencing to assemble and annotate mt genomes and reconstruct phylogenies for comparisons to phylogenies inferred from hundreds of nuclear loci obtained from the same samples. The datasets comprised 108 hexacorals and 94 octocorals representing all orders and > 50% of extant families. Results indicated rampant discordance between datasets at every taxonomic level. This discordance is not attributable to substitution saturation, but rather likely caused by introgressive hybridization and unique properties of mt genomes, including slow rates of evolution driven by strong purifying selection and substitution rate variation. Strong purifying selection across the mt genomes caution their use in analyses that rely on assumptions of neutrality. Furthermore, unique properties of the mt genomes were noted, including genome rearrangements and the presence of nad5 introns. Specifically, we note the presence of the homing endonuclease in ceriantharians. This large dataset of mitochondrial genomes further demonstrates the utility of off-target reads generated from target-capture data for mt genome assembly and adds to the growing knowledge of anthozoan evolution.

ANALYSIS OF YIELD AND FIBER QUALITY TRAITS IN INTRASPECIFIC AND INTERSPECIFIC HYBRIDS OF COTTON

The present study, comprising an evaluation of cotton amphidiploid hybrids and their families for yield and fiber quality traits, commenced from 2007 to 2022 at the Chirchik State Pedagogical University, Tashkent, Uzbekistan. The amphidiploid hybrids’ creation was through interspecific hybridization of Gossypium hirsutum subsp. euhirsutum cultivar Kelajak × F1 (G. arboreum subsp. perenne × G. arboreum subsp. obtusifolium var. indicum) and experimental polyploidy, with genetically enriched new genotypes obtained. According to genetic variability, a considerable variation showed based on F1–F6 populations belonging to various clusters for the traits boll weight (2.3–6.21 g), 1000-seed weight (67.3–125.529 g), fiber length (24.9–34.4125 mm), fiber yield (31.4%–40.26%), and fiber index (6.3–7.5875 g). Furthermore, among the F6 G. hirsutum subsp. euhirsutum cultivar Kelajak × F1 (G. arboreum subsp. perenne × G. arboreum subsp. obtusifolium var. indicum) combination families, the promising genotypes selected gave the highest trait values for boll weight (6.6 ± 0.13 g – Family- 41), 1000-seed weight (125.8 ± 3.48 g – Family-59), fiber yield (40.3% ± 0.65% – Family-59), fiber index (8.5 ± 0.23 g – Family-59), and fiber length (34.5 ± 0.16 mm – Family-8). Genotype evaluation using cluster analysis allows the prediction of cotton families with a better combination of traits. Introgressive hybrids created based on the early maturing families, viz., Family-5, Family-8, Family- 13, Family-14, Family-41, and Family-59, with high yields and fiber indices attained inclusion in the Cotton Gene Pool, Uzbekistan (Certificate of the Academy of Sciences of the Republic of Uzbekistan No. 4/1255-2635 dated November 26, 2020). The promising families selected based on their best performance included F5 (G. hirsutum L. × F1 [G. arboreum L. × G. arboreum L.], Family-5, Family-8, Family-13, Family-14, and Family-59) and F6 (G. hirsutum L. × F1 [G. arboreum L. × G. arboreum L.], Family-5, Family-13, and Family-59), with the said cotton gene pool as valuable recombinants benefiting future breeding programs.

Multiple colonizations and hybridization of a freshwater fish group on a satellite island of Sulawesi

Repeated colonizations and resultant hybridization may increase lineage diversity on an island if introgression occurs only in a portion of the indigenous island lineage. Therefore, to precisely understand how island biodiversity was shaped, it is essential to reconstruct the history of secondary colonization and resultant hybridization both in time and space. In this study, we reconstructed the history of multiple colonizations of the Oryzias woworae species group, a freshwater fish group of the family Adrianichthyidae, from Sulawesi Island to its southeast satellite island, Muna Island. Phylogenetic and species tree analyses using genome-wide single-nucleotide polymorphisms revealed that all local populations on Muna Island were monophyletic, but that there were several genetically distinct lineages within the island. Population structure and phylogenetic network analyses demonstrated that colonization of this island occurred more than once, and that secondary colonization and resultant introgressive hybridization occurred only in one local population on the island. The spatially heterogeneous introgression induced by the multiple colonizations were also supported by differential admixture analyses. In addition, the differential admixture analyses detected reverse colonization from Muna Island to the Sulawesi mainland. Coalescence-based demographic inference estimated that these mutual colonizations occurred during the middle to late Quaternary period, during which sea level repeatedly declined; this indicates that the colonizations occurred via land bridges. We conclude that these mutual colonizations between Muna Island and the Sulawesi mainland, and the resultant spatially heterogeneous introgression shaped the current biodiversity of this species group in this area.

Coexistence of European hares and Alpine mountain hares in the Alps: what drives the occurrence and frequency of their hybrids?

AbstractAs a glacial relict species, mountain hares are adapted to cold and snowy conditions. Conversely, European hares originate from the grasslands of the Middle East and spread from there throughout low‐lying agricultural areas of Europe. Mountain hares and European hares generally occur allopatrically, however, sympatry occurs in some areas. In sympatric areas, introgressive hybridisation poses a threat to the Alpine mountain hare by reducing its genetic integrity. Introgressed individuals can be found in both species but are far more frequent in European hares than in mountain hares. The ecology of hybrids is poorly known in these species. To examine the Alpine mountain hare and European hare populations in the Alps with a particular focus on the occurrence and ecology of their hybrids, we performed molecular genetic analysis of hare faecal samples collected in four study areas in the Alps in South Tyrol for three winters and compared habitat associations of the genotyped samples. We recorded 150 individuals (i.e. 14 hybrids, 25 European hares and 111 Alpine mountain hares). Four introgressed individuals were at levels consistent with F2 hybrids, whereas the others showed an older interspecific gene flow. We found that hybrid faeces tended to be at lower elevations compared to those of Alpine mountain hare but at higher elevations than those of the European hare. The frequency of Alpine mountain hares decreased as the proportion of Alpine grassland increased but was positively correlated with the proportion of dwarf shrub heaths. No effect of vegetation type was found for the frequency of European hares and hybrids. Our results support the widely raised concerns that the European hare, as a generalist, is a strong competitor with the Alpine mountain hare in the Alpine ecosystem in the time of global climate change.

Digest: Massive mixing and merging of Madagascar Gemsnakes.

Introgressive hybridization can give rise to reticulated patterns in a phylogeny. In a recent study, DeBaun et al. (2023) detected 12 reticulation events across the phylogeny of the Madagascar Gemsnakes, suggesting that their evolutionary history cannot be captured in a bifurcating tree. Moreover, identifying the true network of a group is difficult when using only available extant data. The evolution of these snakes might thus be even more tangled than we currently think.

Phylogenetic relationship and comparative analysis of the main Bupleuri Radix species in China.

Bupleuri Radix (Chaihu) is a famous traditional Chinese medicine derived from Bupleurum, Apiaceae. The origin of cultivated Chaihu germplasm in China is unclear, which has led to unstable Chaihu quality. In this study, we reconstructed the phylogeny of the main Chaihu germplasm species in China and identified potential molecular markers to authenticate its origin. Three Bupleurum species (eight individuals), B. bicaule, B. chinense, and B. scorzonerifolium, were selected for genome skimming. Published genomes from B. falcatum and B. marginatum var. stenophyllum were used for comparative analysis. Sequences of the complete plastid genomes were conserved with 113 identical genes ranging from 155,540 to 155,866 bp in length. Phylogenetic reconstruction based on complete plastid genomes resolved intrageneric relationships of the five Bupleurum species with high support. Conflicts between the plastid and nuclear phylogenies were observed, which were mainly ascribed to introgressive hybridization. Comparative analysis showed that noncoding regions of the plastomes had most of the variable sequences. Eight regions (atpF-atpH, petN-psbM, rps16-psbK, petA-psbJ, ndhC-trnV/UAC and ycf1) had high divergence values in Bupleurum species and could be promising DNA barcodes for Chaihu authentication. A total of seven polymorphic cpSSRs and 438 polymorphic nSSRs were detected across the five Chaihu germplasms. Three photosynthesis-related genes were under positive selection, of which accD reflected the adaptation fingerprint of B. chinense to different ecological habitats. Our study provides valuable genetic information for phylogenetic investigation, germplasm authentication, and molecular breeding of Chaihu species.

Genome-wide SNPs reveal recurrent waves of speciation in niche-pockets, in Europe's most venomous snake.

Within the Balkan Peninsula, topographic and climatic agents have promoted biodiversity and shaped the speciation history of many ectotherms. Here, we targeted an iconic European reptile, the nose-horned viper species-complex (Vipera ammodytes), and explored its spatial and temporal evolution. We (1) utilized genome-wide SNPs to infer genetic structure and build a time-calibrated species-tree, and (2) applied species distribution modeling (SDM) with niche-divergence tests among major phylogenomic clades. Geographically structured genetic diversity was found. Cycles of recurrent isolation and expansion during glacial-interglacial periods led to allopatric speciation and to secondary contacts and formation of multiple hybrid zones throughout the Balkan Peninsula. Deep divergence is still detected among populations separated by old and imminent biogeographical barriers (e.g. Pindos Mountain Range, the Cyclades islands etc.), but in most cases speciation is incomplete. At the other end of the speciation continuum, we recognize two well-differentiated lineages, currently lacking any evidence of gene-flow; one is distributed in the Northwestern Balkans and the other in the Southeastern Balkans, further expanding into Asia. Despite their split 5 Mya, there is no evidence of ecological divergence, as speciation probably occurred in niche-pockets of analogous environments. These two lineages probably represent different species, while V. transcaucasiana does not merit species-status. By comparing the genomic phylogenies to an updated mitochondrial one, we propose an evolutionary scenario that resolves all mito-nuclear conflicts, according to which the history of the V. ammodytes species-complex was shaped by complex processes, including a major event of introgressive hybridization with asymmetric mitochondrial capture.

Primerdiffer: a python command-line module for large-scale primer design in haplotype genotyping.

Primer design is a routine practice for modern molecular biology labs. Bioinformatics tools like primer3 and primer-blast have standardized the primer design for a specific region. However, large-scale primer design, especially for genome-wide screening, is still a labor-intensive job for most wet-lab researchers using these pipelines. Here, we present the primerdiffer pipeline, which can be used to batch design primers that differentiate haplotypes on a large scale with precise false priming checking. This command-line interface (CLI) pipeline includes greedy primer search, local and global in silico PCR-based false priming checking, and automated best primer selection. The local CLI application provides flexibility to design primers with the user's own genome sequences and specific parameters. Some species-specific primers designed to genotype the hybrid introgression strains from Caenorhabditis briggsae and Caenorhabditis nigoni have been validated using single-worm PCR. This pipeline provides the first CLI-based large-scale primer design tool to differentiate haplotypes in any targeted region. The open-source python modules are available at github (https://github.com/runsheng/primerdiffer, https://github.com/runsheng/primervcf) and Python package index (https://pypi.org/project/primerdiffer/, https://pypi.org/project/primervcf/).

Landscape factors and allochthonous congeneric species influence Callithrix aurita occurrence in Brazilian Atlantic Forest remnants.

The buffy-tufted-ear marmoset (Callithrix aurita) is a small primate endemic to the Brazilian Atlantic Forest biome, and one of the 25 most endangered primates in the world, due to fragmentation, loss of habitat, and invasion by allochthonous Callithrix species. Using occurrence data for C. aurita from published data papers, we employed model selection using Akaike Information Criterion corrected for small samples and cumulative AICc weight (w +) to evaluate whether fragment size, distance to fragments with allochthonous species, altitude, connectivity, and surrounding matrices influence the occurrence of C. aurita within its distributional range. Distance to fragments with C. jacchus (w + = 0.94) and nonvegetated areas (w + = 0.59) correlated negatively with C. aurita occurrence. Conversely, the percentage of agriculture and pasture mosaic (w + = 0.61) and the percentage of savanna formation (w + = 0.59) in the surrounding matrix correlated positively with C. aurita occurrence. The findings indicate that C. aurita is isolated in forest fragments surrounded by potentially inhospitable matrices, along with proximity of a more generalist and invasive species, thereby increasing the possibility of introgressive hybridization. The findings also highlighted the importance of landscape elements and allochthonous congeneric species for C. aurita conservation, besides indicating urgency for allochthonous species management. Finally, the approach used here can be applied to improve conservation studies of other endangered species, such as C. flaviceps, which is also endemic to the Brazilian Atlantic Forest and faces the same challenges.

Prepping for climate change by introgressive hybridization

Species and populations may adapt to climate change by microevolutionary processes. However, standing genetic variation can be insufficient for this to occur. An interesting new study of a system of rainbowfish species shows that intraspecific hybridization enriches gene pools with adaptive variation that may allow persistence in a changing climate.

Zootechnical Brown Trout (Salmo trutta L. 1758) Ovarian Fluid Fails to Upregulate the Swimming Performances of Native Mediterranean Brown Trout (Salmo cettii Rafinesque, 1810) Sperm in the Biferno River

In external fertilizer fish, ovarian fluid (OF) seems to play a key role in fertilization success, improving spermatozoa swimming performance. These OF/sperm interaction mechanisms are frequently species-specific and/or population-specific and could decrease the risk of genetic introgression of wild populations from introduced or escaped zootechnical individuals. The Mediterranean brown trout (Salmo cettii) is threatened by genetic introgression with strains of domestic brown trout (Salmo trutta) that were introduced for recreational purposes. The aim of our study was to test if native S. cettii females, rather than zootechnical S. trutta, produce OF with a greater ability to upregulate the sperm motility of conspecific males. Thus, we compared the sperm swimming performances of males inhabiting the Biferno River (Molise region—Southern Italy) activated in native S. cettii vs. zootechnical S. trutta female’s OFs. In our study, native females’ OFs (20% diluted), compared to spring water, has the ability to significantly boost the sperm performance of the autochthonous males, while zootechnical S. trutta fails. These preliminary results suggest that OF-sperm interactions could potentially influence or direct the hybridization mechanisms involving the native Mediterranean trout inhabiting the Biferno River and the domestic lineage of brown trout introduced in the past.

MALDI-TOF: A new tool for the identification of Schistosoma cercariae and detection of hybrids.

Schistosomiasis is a neglected water-born parasitic disease caused by Schistosoma affecting more than 200 million people. Introgressive hybridization is common among these parasites and raises issues concerning their zoonotic transmission. Morphological identification of Schistosoma cercariae is difficult and does not permit hybrids detection. Our objective was to assess the performance of MALDI-TOF (Matrix Assistated Laser Desorption-Ionization-Time Of Flight) mass spectrometry for the specific identification of cercariae in human and non-human Schistosoma and for the detection of hybridization between S. bovis and S. haematobium. Spectra were collected from laboratory reared molluscs infested with strains of S. haematobium, S. mansoni, S. bovis, S. rodhaini and S. bovis x S. haematobium natural (Corsican hybrid) and artificial hybrids. Cluster analysis showed a clear separation between S. haematobium, S. bovis, S. mansoni and S. rodhaini. Corsican hybrids are classified with those of the parental strain of S. haematobium whereas other hybrids formed a distinct cluster. In blind test analysis the developed MALDI-TOF spectral database permits identification of Schistosoma cercariae with high accuracy (94%) and good specificity (S. bovis: 99.59%, S. haematobium 99.56%, S. mansoni and S. rodhaini: 100%). Most misidentifications were between S. haematobium and the Corsican hybrids. The use of machine learning permits to improve the discrimination between these last two taxa, with accuracy, F1 score and Sensitivity/Specificity > 97%. In multivariate analysis the factors associated with obtaining a valid identification score (> 1.7) were absence of ethanol preservation (p < 0.001) and a number of 2-3 cercariae deposited per well (p < 0.001). Also, spectra acquired from S. mansoni cercariae are more likely to obtain a valid identification score than those acquired from S. haematobium (p<0.001). MALDI-TOF is a reliable technique for high-throughput identification of Schistosoma cercariae of medical and veterinary importance and could be useful for field survey in endemic areas.

Epistatic QTLs for yield heterosis in tomato

Controlled population development and genome-wide association studies have proven powerful in uncovering genes and alleles underlying complex traits. An underexplored dimension of such studies is the phenotypic contribution of nonadditive interactions between quantitative trait loci (QTLs). Capturing of such epistasis in a genome-wide manner requires very large populations to represent replicated combinations of loci whose interactions determine phenotypic outcomes. Here, we dissect epistasis using a densely genotyped population of 1,400 backcross inbred lines (BILs) between a modern processing tomato inbred (Solanum lycopersicum) and the Lost Accession (LA5240) of a distant, green-fruited, drought-tolerant wild species, Solanum pennellii. The homozygous BILs, each harboring an average of 11 introgressions and their hybrids with the recurrent parents, were phenotyped for tomato yield components. Population-wide mean yield of the BILs was less than 50% of that of their hybrids (BILHs). All the homozygous introgressions across the genome reduced yield relative to recurrent parent, while several QTLs of the BILHs independently improved productivity. Analysis of two QTL scans showed 61 cases of less-than-additive interactions and 19 cases of more-than-additive interactions. Strikingly, a single epistatic interaction involving S. pennellii QTLs on chromosomes 1 and 7, that independently did not affect yield, increased fruit yield by 20 to 50% in the double introgression hybrid grown in irrigated and dry fields over a period of 4 y. Our work demonstrates the power of large, interspecific controlled population development to uncover hidden QTL phenotypes and how rare epistatic interactions can improve crop productivity via heterosis.

DNA barcoding of Chinese snakes reveals hidden diversity and conservation needs.

DNA barcoding has greatly facilitated studies of taxonomy, biodiversity, biological conservation, and ecology. Here, we establish a reliable DNA barcoding library for Chinese snakes, unveiling hidden diversity with implications for taxonomy, and provide a standardized tool for conservation management. Our comprehensive study includes 1638 cytochrome c oxidase subunit I (COI) sequences from Chinese snakes that correspond to 17 families, 65 genera, 228 named species (80.6% of named species) and 36 candidate species. A barcode gap analysis reveals gaps, where all nearest neighbour distances exceed maximum intraspecific distances, in 217 named species and all candidate species. Three species-delimitation methods (ABGD, sGMYC, and sPTP) recover 320 operational taxonomic units (OTUs), of which 192 OTUs correspond to named and candidate species. Twenty-eight other named species share OTUs, such as Azemiops feae and A. kharini, Gloydius halys, G. shedaoensis, and G. intermedius, and Bungarus multicinctus and B. candidus, representing inconsistencies most probably caused by imperfect taxonomy, recent and rapid speciation, weak taxonomic signal, introgressive hybridization, and/or inadequate phylogenetic signal. In contrast, 43 species and candidate species assign to two or more OTUs due to having large intraspecific distances. If most OTUs detected in this study reflect valid species, including the 36 candidate species, then 30% more species would exist than are currently recognized. Several OTU divergences associate with known biogeographic barriers, such as the Taiwan Strait. In addition to facilitating future studies, this reliable and relatively comprehensive reference database will play an important role in the future monitoring, conservation, and management of Chinese snakes.

Introgressive hybridization in the west Pacific pen shells (genus Atrina): Restricted interspecies gene flow within the genome.

A compelling interest in marine biology is to elucidate how species boundaries between sympatric free-spawning marine invertebrates such as bivalve molluscs are maintained in the face of potential hybridization. Hybrid zones provide the natural resources for us to study the underlying genetic mechanisms of reproductive isolation between hybridizing species. Against this backdrop, we examined the occurrence of introgressive hybridization (introgression) between two bivalves distributed in the western Pacific margin, Atrina japonica and Atrina lischkeana, based on single-nucleotide polymorphisms (SNPs) derived from restriction site-associated DNA sequencing. Using 1066 ancestry-informative SNP sites, we also investigated the extent of introgression within the genome to search for SNP sites with reduced interspecies gene flow. A series of our individual-level clustering analyses including the principal component analysis, Bayesian model-based clustering, and triangle plotting based on ancestry-heterozygosity relationships for an admixed population sample from the Seto Inland Sea (Japan) consistently suggested the presence of specimens with varying degrees of genomic admixture, thereby implying that the two species are not completely isolated. The Bayesian genomic cline analysis identified 10 SNP sites with reduced introgression, each of which was located within a genic region or an intergenic region physically close to a functional gene. No, or very few, heterozygotes were observed at these sites in the hybrid zone, suggesting that selection acts against heterozygotes. Accordingly, we raised the possibility that the SNP sites are within genomic regions that are incompatible between the two species. Our finding of restricted interspecies gene flow at certain genomic regions gives new insight into the maintenance of species boundaries in hybridizing broadcast-spawning molluscs.

Microscopical palynology: Birch woodland expansion and species hybridisation coincide with periods of climate warming during the Holocene epoch in Iceland.

Introgressive hybridisation between arctic dwarf birch (Betula nana) and European downy birch (B.pubescens) is relatively common in natural woodlands in Iceland. As dwarf birch is a diploid species and downy tree birch a tetraploid species, their hybrids are triploid. In the introgression process, triploid hybrids, which are partially fertile, can backcross with the parental species, producing progenies comprising introgressed diploid, triploid and tetraploid plants. Triploid plants produce both normal triporate pollen (with three pores) and abnormal, aborted pollen, due to dysfunctional meiosis. The type of pollen abnormality that can be detected and quantified is non-triporate pollen (with four or more pores in the pollen wall). We therefore used the presence of non-triporate pollen as a marker to trace birch hybridisation in the past. In the current study we examined fossil pollen in samples from Holocene sediments from three locations: Grímsnes (SW), Eyjafjördur (N) and Thistilsfjördur (NE Iceland). All three peat monoliths had the starting age of 10.3cal. ka BP. Ages were calibrated based on known tephra layers and by radiocarbon dating. The size of Betula pollen grains was measured, and the species proportions calculated from size. Non-triporate grains were detected in samples from all three locations and throughout the Holocene, but with different frequencies. The peaks of intense hybridisation followed birch woodland expansion in two major periods of the Holocene, both coinciding with a warming of climate. The first period occurred in the Early Holocene, around 9.5-7cal. ka BP, when the climate warmed rapidly after deglaciation. The second period occurred around 5-3.5cal. ka BP, well within the mid-Holocene Northern Hemisphere warming. A new wave of birch hybridisation appears to have started in the last few decades as the climate has warmed. Birch woodlands are likely to become more widespread. Introgressed shrub birch is likely to be more competitive over dwarf birch.

Genomic analysis, trajectory tracking, and field surveys reveal sources and long-distance dispersal routes of wheat stripe rust pathogen in China

Identifying sources of phytopathogen inoculum and determining their contributions to disease outbreaks are essential for predicting disease development and establishing control strategies. Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat stripe rust, is an airborne fungal pathogen with rapid virulence variation that threatens wheat production through its long-distance migration. Because of wide variation in geographic features, climatic conditions, and wheat production systems, Pst sources and related dispersal routes in China are largely unclear. In the present study, we performed genomic analyses of 154 Pst isolates from all major wheat-growing regions in China to determine Pst population structure and diversity. Through trajectory tracking, historical migration studies, genetic introgression analyses, and field surveys, we investigated Pst sources and their contributions to wheat stripe rust epidemics. We identified Longnan, the Himalayan region, and the Guizhou Plateau, which contain the highest population genetic diversities, as the Pst sources in China. Pst from Longnan disseminates mainly to eastern Liupan Mountain, the Sichuan Basin, and eastern Qinghai; that from the Himalayan region spreads mainly to the Sichuan Basin and eastern Qinghai; and that from the Guizhou Plateau migrates mainly to the Sichuan Basin and the Central Plain. These findings improve our current understanding of wheat stripe rust epidemics in China and emphasize the need for managing stripe rust on a national scale.

Methods to detect and characterize introgression.

Introgression, also known as introgressive hybridization, refers to the process that genetic components from the gene pool of one population transfer to the other via constant backcrossing. Introgression is widespread in nature, which plays important roles in increasing genetic diversity and improving adaptability to the environment, and in turn, influences the evolutionary progress of animals, plants and humans. Being as an important evolutionary event, researchers pay great attention to the detection of introgression, the introgression direction, the introgression timing, the pattern of introgression and so on. With the rapid development of high-throughput sequencing technologies, methods to detect and characterize introgression based on genome-wide data are continuously developed. In this review, we summarize a series of methods for introgression detection, and introduce the design principles and applications of these methods. We also discuss the maintenance and selection of gene segments after introgression. This review provides a relatively comprehensive reference for the studies on introgression.

Torymus sinensis against the invasive chestnut gall wasp: Evaluating the physiological host range and hybridization risks of a classical biological control agent

BackgroundA common strategy to limit the negative impact of biological invasions is biological control through the release of specialized alien natural enemies. However, biological control plans are not without risks, which include parasitism of native hosts and hybridization with related native species, particularly those that are potential natural enemies of the invasive species. Here, we evaluate these potential risks resulting from the introduction of the parasitoid wasp Torymus sinensis (Hymenoptera: Torymidae) in Europe to control the invasive Asian chestnut gall wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae). ResultsWe found that, under laboratory conditions, the physiological host range of T. sinensis includes several native non-target species of Cynipidae, with oviposition observed on the galls of 8 of the 11 species tested. However, physiological host range of T. sinensis appears to be limited under field conditions, as we observed only one parasitized gall of Andricus curvator in the field. Regarding hybridization, inter-species mating between T. sinensis and its phylogenetically closest native Torymus species was not observed in the laboratory. Moreover, discordance between nuclear (ITS2) and mitochondrial (coxI) data does not support the presence of genetic introgression, suggesting that hybridization between T. sinensis and native Torymus species does not occur. In addition, we cite and discuss the unexpected presence of one individual of the related alien species Torymus beneficus in Spain. ConclusionOur results suggest that T. sinensis may negatively impact several non-target species, highlighting the need for careful monitoring of the extent of such undesired behaviour and its effects on the native fauna.

Pedigree or identity? How genome editing can fundamentally change the path for crop development.

AbstractNovel alleles can now be directly written into related genomes by sequence identity, thus removing the resource-intensive process of trait introduction by genetic introgression and eliminate the loss of genetic diversity that typically results from introgression bottlenecks.