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The rapid expansion of wild pigs (Sus scrofa) throughout the United States has been fueled by unlawful introductions, with invasive populations causing extensive crop losses, damaging native ecosystems, and serving as a reservoir for disease. Multiple states have passed laws prohibiting the possession or transport of wild pigs. However, genetic and phenotypic similarities between domestic pigs and invasive wild pigs—which overwhelmingly represent domestic pig and wild boar hybrids—pose a challenge for the enforcement of such regulations. We sought to exploit wild boar ancestry as a common attribute among the vast majority of invasive wild pigs as a means of genetically differentiating wild pigs from breeds of domestic pig found within the United States. We organized reference high‐density single nucleotide polymorphism genotypes (1039 samples from 33 domestic breeds and 382 samples from 16 wild boar populations) into five genetically cohesive reference groups: mixed‐commercial breeds, Durocs, heritage breeds, primitive breeds, and wild boar. Building upon well‐established genetic clustering approaches, we structured the test statistic to describe the difference in the likelihood of a given genotype's ancestry vectors (sensu genetic clustering analysis) if derived strictly from the four described domestic pig reference groups versus allowing for admixture from the wild boar group. By fitting statistical distributions to test statistics of reference domestic pigs, we characterized the distribution of the null hypothesis that a given genotype descends strictly from domestic pig reference groups. We tested the approach with simulated genotypes and empirical data from an additional 29 breeds of domestic pig represented by 435 unique genotypes; all associated test statistics for simulated and empirical domestic pig challenge sets fell within the distribution of reference domestic pigs. We then evaluated 6566 invasive wild pigs sampled across the contiguous United States, of which 63% exceeded the maximum threshold for domestic pigs and could be statistically classified as possessing wild boar ancestry. This approach provides a scientific foundation to enforce regulations prohibiting the possession of this destructive invasive species. Further, this computationally efficient and generalizable approach could be readily adapted to quantify gene flow among ecological systems of conservation or management concern. [ABSTRACT FROM AUTHOR]

Hybridization—the interbreeding of different species—plays an integral role in the evolution of numerous bird species. However, it remains unclear how widespread this phenomenon is within and across different bird groups. Estimating the incidence of hybridization in different bird lineages can inform comparative analyses to uncover the evolutionary and ecological forces that promote or prevent the formation of hybrids. Estimates on a species level have varied from about 10% to almost 20% of hybridizing bird species. The variation among the latest estimates largely depends on the choice of global species checklists with differing decisions on the taxonomic status of certain (sub)species. However, the hybrid records in these estimates have generally been taken at face value. Detailed assessments of these records revealed that some cases are unreliable or incorrect. Removing of these faulty records and discovery of novel hybrids will result in a fluctuating percentage of hybridizing species that can best be captured in a living document (e.g., a regularly updated website or checklist). Estimating hybridization on an individual level is more challenging. A first attempt, using citizen science data from the eBird project, reported 0.064% hybrid individuals in the United States. This percentage is probably an underestimate due to underreporting of hybrids by birdwatchers and remains to be finetuned by considering other confounding factors, such as spatial and temporal variation in hybridization dynamics. Future efforts in estimating avian hybridization will need to rely on a combination of data sources and techniques, such as genetics, museum specimens, and citizen science. [ABSTRACT FROM AUTHOR]

Pairs of species that exhibit broadly overlapping distributions, and multiple geographically isolated contact zones, provide opportunities to investigate the mechanisms of reproductive isolation. Such naturally replicated systems have demonstrated that hybridization rates can vary substantially among populations, raising important questions about the genetic basis of reproductive isolation. The topminnows, Fundulus notatus and F. olivaceus, are reciprocally monophyletic, and co‐occur in drainages throughout much of the central and southern United States. Hybridization rates vary substantially among populations in isolated drainage systems. We employed genome‐wide sampling to investigate geographic variation in hybridization, and to assess the possible importance of chromosome fusions to reproductive isolation among nine separate contact zones. The species differ by chromosomal rearrangements resulting from Robertsonian (Rb) fusions, so we hypothesized that Rb fusion chromosomes would serve as reproductive barriers, exhibiting steeper genomic clines than the rest of the genome. We observed variation in hybridization dynamics among drainages that ranged from nearly random mating to complete absence of hybridization. Contrary to predictions, our use of genomic cline analyses on mapped species‐diagnostic SNP markers did not indicate consistent patterns of variable introgression across linkage groups, or an association between Rb fusions and genomic clines that would be indicative of reproductive isolation. We did observe a relationship between hybridization rates and population phylogeography, with the lowest rates of hybridization tending to be found in populations inferred to have had the longest histories of drainage sympatry. Our results, combined with previous studies of contact zones between the species, support population history as an important factor in explaining variation in hybridization rates. [ABSTRACT FROM AUTHOR]

Hybridization is among the evolutionary mechanisms most frequently hypothesized to drive the success of invasive species, in part because hybrids are common in invasive populations. One explanation for this pattern is that biological invasions coincide with a change in selection pressures that limit hybridization in the native range. To investigate this possibility, we studied the introduction of the brown anole (Anolis sagrei) in the southeastern United States.We find that native populations are highly genetically structured. In contrast, all invasive populations show evidence of hybridization among native-range lineages. Temporal sampling in the invasive range spanning 15 y showed that invasive genetic structure has stabilized, indicating that large-scale contemporary gene flow is limited among invasive populations and that hybrid ancestry is maintained. Additionally, our results are consistent with hybrid persistence in invasive populations resulting from changes in natural selection that occurred during invasion. Specifically, we identify a large-effect X chromosome locus associated with variation in limb length, a well-known adaptive trait in anoles, and show that this locus is often under selection in the native range, but rarely so in the invasive range. Moreover, we find that the effect size of alleles at this locus on limb length is much reduced in hybrids among divergent lineages, consistent with epistatic interactions. Thus, in the native range, epistasis manifested in hybrids can strengthen extrinsic postmating isolation. Together, our findings show how a change in natural selection can contribute to an increase in hybridization in invasive populations. [ABSTRACT FROM AUTHOR]

In plant species, variation in levels of clonality, ploidy and interspecific hybridization can interact to influence geographic patterns of genetic diversity. These factors commonly vary in plants that specialize on saline habitats (halophytes) and may play a role in how they adapt to salinity variation across their range. One such halophyte is the turfgrass and emerging genomic model system seashore paspalum (Paspalum vaginatum Swartz). To investigate how clonal propagation, ploidy variation, and interspecific hybridization vary across ecotypes and local salinity levels in wild P. vaginatum, we employed genotyping‐by‐sequencing, cpDNA sequencing and flow cytometry in 218 accessions representing > 170 wild collections from throughout the coastal southern United States plus USDA germplasm. We found that the two morphologically distinct ecotypes of P. vaginatum differ in their adaptive strategies. The fine‐textured ecotype is diploid and appears to reproduce in the wild both sexually and by clonal propagation; in contrast, the coarse‐textured ecotype consists largely of clonally‐propagating triploid and diploid genotypes. The coarse‐textured ecotype appears to be derived from hybridization between fine‐textured P. vaginatum and an unidentified Paspalum species. These clonally propagating hybrid genotypes are more broadly distributed than clonal fine‐textured genotypes and may represent a transition to a more generalist adaptive strategy. Additionally, the triploid genotypes vary in whether they carry one or two copies of the P. vaginatum subgenome, indicating multiple evolutionary origins. This variation in subgenome composition shows associations with local ocean salinity levels across the sampled populations and may play a role in local adaptation. [ABSTRACT FROM AUTHOR]

When working with a citizen science database like eBird, there are many possible ways to filter or subsample observations. Here, we discuss the potential biases and assumptions that surround different subsampling approaches or filtering that can be done to the eBird database. Restricting observations to species that are known to frequently hybridize, a specific time of the year, or a specific location, has the potential to greatly inflate the calculated per‐individual rate of hybridization. Such filtering also assumes that researchers know a birds' capacity to hybridize with all other species in its range, which we argue is an unfounded assumption. We ultimately conclude that a limited filtering approach is ideal when using a citizen science database to attempt to address a broad question such as: what is the per individual rate of hybridization across all of the bird species in the United States? [ABSTRACT FROM AUTHOR]

The rate of hybridization among taxa is a central consideration in any discussion of speciation, but rates of hybridization are difficult to estimate in most wild populations of animals. We used a successful citizen science dataset, eBird, to estimate the rates of hybridization for wild birds in the United States. We calculated the frequency at which hybrid individuals belonging to different species, families, and orders of birds were observed. Between 1 January 2010 and 31 December 2018, a total of 334,770,194 species records were reported to eBird within the United States. Of this total, 212,875 or 0.064% were reported as hybrids. This estimate is higher than the rate of hybridization (0.00167%) reported by Mayr based on impressions from a career studying museum specimens. However, if the 10 most influential hybrid species are removed from the eBird dataset, the rate of hybridization decreases substantially to about 0.009%. We conclude that the rate of hybridization for individuals in most bird species is extremely low, even though the potential for birds to produce fertile offspring through hybrid crosses is high. These findings indicate that there is strong prezygotic selection working in most avian species. [ABSTRACT FROM AUTHOR]

A recent study demonstrated that British red foxes introduced to the mid-Atlantic coastal plain (ACP) of the eastern United States during the late 18th century successfully interbred with indigenous American red foxes despite half a million year's divergence. However, a large disparity in frequency of European mitochondria (27%) versus Y chromosomes (1%) left unclear the magnitude of genetic exchange. We sought to quantify genomic introgression using 35 autosomal and 5 X-chromosome ancestry-informative markers (AIMs) in conjunction with diagnostic Y chromosome single nucleotide polymorphism (Y-SNP) markers to characterize the modern state of red foxes in the eastern United States and to gain insight into the potential role of reproductive barriers. European admixture was highest in the ACP and apparently restricted to the central eastern United States. We estimated only slightly (and nonsignificantly) European ancestry in autosomal than X-chromosome markers. European ancestry from autosomal and X-chromosome markers (36.4%) was higher than the corresponding mitochondrial (mt) DNA estimate (26.4%) in the ACP. Only 1 of 124 males (<1%) in the ACP had European Y chromosomes, which was similar to the neighboring regions, in which 2 of 99 (2%) males carried a European Y chromosome (the same haplotype). Although we could not rule out drift as the cause of low European Y-chromosome frequency, results were also consistent with F1 male infertility. In the future, more extensive genomic sequencing will enable a more thorough investigation of possible barrier genes on the X chromosome as well as throughout the genome. [ABSTRACT FROM AUTHOR]

South Asians, despite their positioning as a "model minority," have not been immune from the consequences of the heightened racist and nationalist rhetoric witnessed lately in the United States. However, such sentiments about the South Asian immigrant community are not new, as they are reflective of a "yellow peril" discourse. This study analyzes South Asian Americans' responses to a TIME Magazine column complaining about their influx into Edison, New Jersey. It first explores the racial formation that the model minority myth, in dialectical relationship with the yellow peril discourse, has produced among South Asians. Through this analysis, this study critically analyzes how South Asian Americans' discourses both reinforce and challenge their racialized status positions and identities as the model minority. [ABSTRACT FROM AUTHOR]

Premise: In plant groups with limited intrinsic barriers to gene flow, it is thought that environmental conditions can modulate interspecific genetic exchange. Oaks are known for limited barriers to gene flow among closely related species. Here, we use Quercus as a living laboratory in which to pursue a fundamental question in plant evolution: Do environmental gradients restrict or promote genetic exchange between species? Methods: We focused on two North American oaks, the rare Quercus dumosa and the widespread Q. berberidifolia. We sampled intensively along a contact zone in California, USA. We sequenced restriction site‐associated DNA markers and measured vegetative phenotype. We tested for genetic exchange, the association with climate, and the effect on phenotype. Results: There is evidence for genetic exchange between the species. Admixed plants are found in areas of intermediate climate, while less admixed plants are found at the extremes of the climatic gradient. Genetic and phenotypic patterns are out of phase in the contact zone; some plants display the phenotype of one species but are genetically associated with another. Conclusions: Our results support the hypothesis that a strong climatic gradient can promote genetic exchange between species. The overall weak correlation between genotype and phenotype in the contact zone between the species suggests that genetic exchange can lead to the breakdown of trait combinations used to define species. This incongruency predicts ongoing problems for conservation of Q. dumosa, with implications for conservation of other oaks. [ABSTRACT FROM AUTHOR]

Control of weeds in cultivated crops is a pivotal component in successful crop production allowing higher yield and higher quality. In rice‐growing regions worldwide, weedy rice (Oryza sativa f. spontanea Rosh.) is a weed related to cultivated rice which infests rice fields. With populations across the globe evolving a suite of phenotypic traits characteristic of weeds and of cultivated rice, varying hypotheses exist on the origin of weedy rice. Here, we investigated the genetic diversity and possible origin of weedy rice in California using 98 simple sequence repeat (SSR) markers and an Rc gene‐specific marker. By employing phylogenetic clustering analysis, we show that four to five genetically distinct biotypes of weedy rice exist in California. Analysis of population structure and genetic distance among individuals reveals diverse evolutionary origins of California weedy rice biotypes, with ancestry derived from indica, aus, and japonica cultivated rice as well as possible contributions from weedy rice from the southern United States and wild rice. Because this diverse parentage primarily consists of weedy, wild, and cultivated rice not found in California, most existing weedy rice biotypes likely originated outside California. [ABSTRACT FROM AUTHOR]

Genetic diversity information can be valuable for establishing successful management strategies for indigenous and invasive species. Here we conducted a genetic assessment of two invasive and one native Tamarix species in South Africa, where all species are known to hybridize. Hybridization can encourage biological invasion by creating unique allele combinations that facilitate invasiveness in plants. Using 9 microsatellite markers, we genotyped 150 individuals from four Tamarix taxa, viz. T. usneoides, T. chinensis , T. ramosissima , and Tamarix hybrids. We investigated the genetic diversity in the indigenous and invasive Tamarix species, and their genetic differentiation in South Africa, and compared the genetic diversity between South African Tamarix hybrids to hybrids from the United States. We aimed to elucidate information useful for the biocontrol efforts against the invasive genotypes and the conservation of the indigenous species. Our results showed that there is clear genetic differentiation between the indigenous and invasive species of Tamarix in South Africa. The indigenous T. usneoides was found to have greater genetic diversity than the exotic T. chinensis , but lower than the alien T. ramosissima. Higher genetic diversity was detected in South African Tamarix hybrids compared to hybrids of the same species from the United States and there is substantial genetic differentiation between Tamarix hybrids from the two countries. Additionally, remote places in the northwest of South Africa contain private alleles suggesting non-polluted indigenous T. usneoides germplasm which should be preserved. These results suggest that there would be minimal risk of non-target effects on the indigenous species should a biocontrol program for the alien invasive species be implemented. • Tamarix species in South Africa have a low to moderate genetic diversity. The low genetic diversity in the invasive Tamarix chinensis is attributed to its autogamous nature. • The genetic diversity of the invasive Tamarix species in South Africa resembles those from its place of origin where exploration for biocontrol agents can be done. • High genetic differentiation between the indigenous T. usneoides and the invasive species suggest that there might be no or minimal non-target effect from biocontrol agents. • Although previous research found hybridization with indigenous species, genetic diversity of the parental species appears unaffected. Instead, the moderate genetic diversity in the indigenous species may be the result of genetic drift due to population fragmentation. • We found evidence of private alleles specific to the indigenous species in some remote unpolluted areas in the Northern Cape. These populations should be considered for conservation of the indigenous germplasm which could be under threat from hybridization with the invasive species. [ABSTRACT FROM AUTHOR]

While over 1400 GW of distributed wind potential has been documented in the United States, less than 0.01% of that has been deployed to date. Significant amounts of renewable resources will need to be deployed in coming years to meet national clean energy goals, making the identification of opportunities and barriers to deployment for this resource a topic of high interest. Wind resource variability, which can cause uncertainty and instability in the grid and affect the number of attainable and beneficial applications the resource can pursue, is often a common hurdle to deployment. Pairing distributed wind with other technologies, such as solar photovoltaics and/or energy storage, however, has the ability to alleviate this issue through generation complementarity and increased dispatchability. Both characteristics have the potential to increase project value across a range of applications from bulk energy to ancillary services. Understanding where and how value differs under various hybrid configurations (e.g., distributed wind with solar, distributed wind with solar and storage) can overcome barriers to deployment and improve the economic vitality of projects. In this study, we describe the potential value impacts of adding solar photovoltaics and/or energy storage to a distributed wind energy installation, provide a qualitative ranking system for each value stream that might be available for the new hybrid power system, and present quantitative results for the potential dollars per year that might be possible for select value streams. From a benefits perspective, we find that hybridizing has the potential to add value to all value streams, with the addition of energy storage providing greater value impact than that of solar photovoltaics. • Value streams involving dispatchability are highly influenced by hybridization. • Some remunerative value streams are not greatly impacted by hybridization. • Hybridizing with energy storage, not just solar, has biggest impact on value. • Solar-wind hybrids have substantial value in states that offer solar renewable energy credits. [ABSTRACT FROM AUTHOR]

Two adelgid predators, Laricobius nigrinus Fender and Laricobius rubidus LeConte, were recently discovered to produce hybrid progeny in the eastern United States. L. rubidus is native to eastern North America where it feeds on pine bark adelgid ( Pineus strobi Hartig) and L. nigrinus is native to western North America and was introduced to the eastern United States in 2003 for biological control of hemlock woolly adelgid ( Adelges tsugae Annand). Currently, L. nigrinus and L. rubidus form a mosaic of hybrid zones throughout the eastern United States. It is not known whether these zones will be maintained over time and whether hybridization will impact the efficacy of biological control or result in displacement of L. rubidus . Sampling from 2007 to 2012 on eastern hemlock ( Tsuga canadensis Carrière) showed a clear increase in L. nigrinus , a decrease in L. rubidus , and a steady proportion of hybrids. Sampling from 2010 to 2012 on both eastern hemlock and white pine ( Pinus strobus L.) at ten sites showed that L. nigrinus was more dominant on hemlock and L. rubidus was more dominant on white pine, which may demonstrate habitat preference and promote segregation between the two species. Site factors were tested for a relationship with the proportion of hybrids. The number of years L. nigrinus had been present at the site was the only factor that showed a relationship. The results suggest that L. nigrinus may displace L. rubidus on hemlock, but not on white pine at sites where they are both present. [ABSTRACT FROM AUTHOR]

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Bighead carp ( Hypophthalmichthys nobilis) and silver carp ( H. molitrix) are invasive species and listed as US federally injurious species under the Lacy Act. They have established populations in much of the Mississippi River Basin ( MRB; Mississippi, Illinois, and Missouri rivers) and are capable of producing fertile hybrids and complex introgression. Characterizing the composition of this admixture requires a large set of high-quality, evolutionarily conserved, diagnostic genetic markers to aid in the identification and management of these species in the midst of morphological ambiguity. Restriction site-associated DNA ( RAD) sequencing of 45 barcoded bighead and silver carp from the United States and China produced reads that were aligned to the silver carp transcriptome yielded 261 candidate single nucleotide polymorphisms ( SNPs) with fixed allelic differences between the two species. We selected the highest quality 112 SNP loci for validation using 194 putative pure-species and F1 hybrids from the MRB and putative bighead carp and silver carp pure species from China ( Amur, Pearl and Yangtze rivers). Fifty SNPs were omitted due to design/amplification failure or lack of diagnostic utility. A total of 57 species-diagnostic SNPs conserved between carp species in US and Chinese rivers were identified; 32 were annotated to functional gene loci. Twenty-seven of the 181 (15%) putative pure species were identified as hybrid backcrosses after validation, including three backcrosses from the Amur River, where hybridization has not been documented previously. The 57 SNPs identified through RAD sequencing provide a diagnostic tool to detect population admixture and to identify hybrid and pure-species Asian carps in the United States and China. [ABSTRACT FROM AUTHOR]

By the 1970s, government-supported eradication campaigns reduced red wolves to a remnant population of less than 100 individuals on the southern border of Texas and Louisiana. Restoration efforts in the region were deemed unpromising because of predator-control programs and hybridization with coyotes. The U.S. Fish and Wildlife Service (USFWS) removed the last remaining red wolves from the wild and placed them in a captive-breeding program. In 1980, the USFWS declared red wolves extinct in the wild. During 1987, the USFWS, through the Red Wolf Recovery Program, reintroduced red wolves into northeastern North Carolina. Although restoration efforts have established a population of approximately 70-80 red wolves in the wild, issues of hybridization with coyotes, inbreeding, and human-caused mortality continue to hamper red wolf recovery. We explore these three challenges and, within each challenge, we illustrate how research can be used to resolve problems associated with red wolf-coyote interactions, effects of inbreeding, and demographic responses to human-caused mortality. We hope this illustrates the utility of research to advance restoration of red wolves. [ABSTRACT FROM AUTHOR]

The article offers information regarding the potential use of gene flow in switchgrass as a biofuel feedstock in the U.S. It mentions that studies conducted to examine the use of switchgrass as a biofuel feedstock began in 1980s. It cites that switchgrass could further expand in the bioenergy sector through various processes like co-firing with coal to produce electricity.

A proliferation of exchanges between film industries in the United States, Europe and Latin America are redefining the Latin American film industry in the twenty-first century. This article considers how these cross-border and cross-cultural flows may inform new ways for understanding national and regional cinemas. In the following discussion, I analyse emerging industrial practices and producers' responses to the new transnational alliances. I follow this by examining the critical debates over the effects that such structural changes may be having on the diversification of narratives and their contribution in the articulation of transforming national and regional identities. [ABSTRACT FROM AUTHOR]

Alpine environments underwent dramatic transformation during glacial-interglacial cycles, with the consequence that geographical, ecological and demographic changes of alpine populations provided the opportunity for formation of neoendemic species. Several biogeographical models have been proposed to account for the unique history of alpine populations, with different expectations of genetic divergence and speciation. The expanding alpine archipelago model proposes that alpine populations expand spatially and demographically during glacial events, dispersing between mountain ranges. Under this model, alpine populations are unlikely to diverge in isolation due to substantial interpopulation gene flow. In contrast, the alpine archipelago refuge model proposes that gene flow during glacial phases is limited and populations expand demographically during interglacial phases, increasing genetic isolation and the likelihood of speciation. We assess these models by reconstructing the evolutionary history of Colias behrii, a morphologically and ecologically distinct alpine butterfly restricted to the California Sierra Nevada. C. behrii exhibits very low genetic diversity at mitochondrial and nuclear loci, limited population structure and evidence of population expansion. C. behrii and Rocky Mountain C. meadii share identical mitochondrial haplotypes, while in contrast, nuclear data indicate common ancestry between C. behrii and Cascades Range Colias pelidne. The conflict in gene genealogies may be a result of recent expansion in North American Colias, but an isolation with migration analysis indicates that genetic patterns in C. behrii might result from differential introgression following hybridization. Based on the timing of population expansion and gene flow between mountain ranges, the expanding alpine archipelago model is supported in C. behrii. [ABSTRACT FROM AUTHOR]

Ulmus pumila is considered an invasive tree in 41 of the United States. In this study, we examined the extent of hybridization in naturalized populations of U. pumila, its impact on genetic diversity and genetic structure and its potential role in explaining the invasion process of U. pumila. Genetic analyses indicated widespread hybridization with native Ulmus rubra in naturalized U. pumila populations. Hybridization increased the genetic diversity of U. pumila populations and affected their genetic structure. The level of genetic diversity in ‘mature’ accessions, many of which may represent original plantings throughout the USA, was high and similar to the diversity of East Asian accessions. Hybridization with the native red elm may play an important role in the success of Siberian elm as an invader in temperate regions of the USA. [ABSTRACT FROM AUTHOR]

When introduced or cultivated plants or animals hybridize with their native relatives, the spread of invasive genes into native populations might have biological, aesthetic, and legal implications. Models suggest that the rate of displacement of native by invasive alleles can be rapid and inevitable if they are favored by natural selection. We document the spread of a few introduced genes 90 km into a threatened native species (the California Tiger Salamander) in 60 years. Meanwhile, a majority of genetic markers (65 of 68) show little evidence of spread beyond the region where introductions occurred. Using computer simulations, we found that such a pattern is unlikely to emerge by chance among selectively neutral markers. Therefore, our results imply that natural selection has favored both the movement and fixation of these exceptional invasive alleles. The legal status of introgressed populations (native populations that are slightly genetically modified) is unresolved by the US Endangered Species Act. Our results illustrate that genetic and ecological factors need to be carefully weighed when considering different criteria for protection, because different rules could result in dramatically different geographic areas and numbers of individuals being protected. [ABSTRACT FROM AUTHOR]

Amorpha georgiana (Fabaceae) is an endangered legume species found in longleaf pine savannas in the Southeastern United States. Approximately 900 individuals and 14 populations remain, most of which are concentrated in North Carolina. Eleven microsatellite loci were used to explore genetic diversity, population structure and recent population bottlenecks using genotypic data from 132 individuals collected at ten different localities. Although A. georgiana is quite rare, it exhibited high levels of genetic diversity (17.7 alleles/locus; Ho = 0.65, HE = 0.75). Most of the genetic variation was found within rather than between populations of this species. The single remaining Georgia population was well differentiated from populations of the Carolinas ( FST > 0.1), which had weaker structure among them ( FST < 0.1). Only a geographically disjunct population showed strong evidence of a recent population bottleneck, perhaps due to a recent founder event. Hybridization with A. herbacea was also detected. For conservation management plans, A. georgiana populations in each geographic region (North Carolina, South Carolina and Georgia) plus a disjunct population in North Carolina (Holly Shelter) should be treated as separate management units for which in situ conservation, including habitat restoration and use of prescribed burns, should ensure persistence of this species and preservation of its evolutionary potential. [ABSTRACT FROM AUTHOR]

The many millions of North American bison in the mid-19th century were reduced to near extinction by the middle 1880s. Plains bison, the subspecies found in the United States, were saved from extinction primarily by 5 private ranchers and the survival of a small herd in what is now Yellowstone National Park. This bottleneck resulted in the present-day plains bison population being descended from less than 100 founders. In addition, many conservation herds have cattle ancestry because of hybridization promoted by these ranchers in the late 1800s and early 1900s. Today, although there are around 500 000 plains bison in North America, only 4% (20 000) are in conservation herds. Only I conservation herd with no known ancestry from cattle has an effective population size of more than 1000. Here I review and evaluate this situation and provide recommendations for the reduction of cattle ancestry, avoidance of inbreeding depression, and maintenance of genetic variation in the conservation herds of bison. [ABSTRACT FROM AUTHOR]

The Ponderosae subsection of the genus Pinus contains numerous taxa in disjunct mountain ranges of southern Arizona and New Mexico, differing for several leaf and cone traits, key among which is the number of leaf needles per fascicle. Trees with three needles are often found together with trees having five needles and mixed numbers. One taxonomic hypothesis is that there are swarms of hybrids between P. ponderosa and P. arizonica. A second hypothesis is that there are spatial mixtures of two separate taxa, five-needle P. arizonica and a "taxon X" containing three needle and mixed needle trees. We genotyped chloroplasts in one putative hybrid swarm on Mt. Lemmon using microsatellite markers and show that cpDNA is almost completely differentiated between two separate morphotypes corresponding to P. arizonica and "taxon X." Little if any introgression has occurred on Mt. Lemmon, and the simplest explanation is that little or no effective hybridization has occurred. Further results indicate that not only is taxon X not of hybrid origin, it is more closely related to nonregional Ponderosae other than P. ponderosa and P. arizonica. The results further suggest that other putative hybrid swarms in the region are also spatial mixtures of distinct taxa. [ABSTRACT FROM AUTHOR]

The article presents a study which found that the genetic analysis of historic western Great Lakes region shows early Canis lupus/lycaon hybridization. The genetic status of wolves in the western Great Lakes region has received widespread attention following the decision to remove them from protection under the U.S. Endangered Species Act. A study of mitochondrial DNA has evoked that the recovered wolf population is not genetically representative of the historic population. The authors found that the DNA profiles of the historic samples are the same as those of extant animals in the region, which suggested that the current Great Lakes wolves are representative of the historic population.

Achillea millefolium agg. is an ecologically most diverse N Hemisphere polyploid complex. Because of ubiqui- tous hybridization and polyploidization, the aggregate is extremely polymorphic and notorious for its difficult taxonomy. AFLP analyses were applied to 61 populations representing most of the known taxa ofA. millefolium agg. Genetic distance methods ofpopulation pairwise FST and Neighbour Joining for tree constructions and the 2D^Euklid algorithm for scatter plots were used to evaluate the AFLP-matrix with 459, mostly polymorphic bands. The aggregate is monophyletic and sister to the subalpine relic A. latiloba-2x from NE Turkish and adjacent Georgian mountains. The seven 2x-species of A. millefolium agg. have differentiated vicariously in Europe/SW Asia and expanded into C and E Asia. Both, the NJ trees and the 2D^Euklid scatterplots demon- strate these 2x as genetically monophyletic and distinct; only A. roseoalba-2x, close to A. asplen~folia-2x, may be the product of hybrid introgression. The polyploids of the aggregate (about 20 taxa and cytotypes) exhibit various combinations of 2x AFLP bands, but in addition also 16.9% of exclusive bands, documenting new genetic variation. Whereas the ALFP trees suggest most of these polyploid taxa to be polyphyletic, the AFLP 2DEuklid scatterplots demonstrate their phyletic coherence. This conflicting evidence apparently is due to wide-spread secondary hybrid merging between sympatric populations ofdifferent polyploid taxa, resulting in geographic instead of phyletic clustering of their populations in the AFLP trees. Available data suggest several parallel reticulating and ascending polyploid lines and their eco-geographical radiations. This has resulted in the origin of eight taxa of 4x, four or five of 6x and three of 8x in Europe and the Caucasus. One of them, A. millefolium subsp. millefolium-6x, also occurs throughout Asia, where two more 4x taxa, one additional 6x and one 8x can be recognized. Finally, from ancestors close to A. asialica s.str.-4x, the A. borealis s.l. dade has originated in N America, where it has radiated with numerous 4x- and 6x-ecotypes into most diverse habitats. Thus, the polyploid complex A. millefolium agg., shaped by successive cycles of differentiation and hybridiza- tion + polyplodization, has expanded stepwise from Europe and SW Asia to E Asia, then to N America and finally world-wide with A. millefolium-6x as a weed. [ABSTRACT FROM AUTHOR]

Drawing on detailed qualitative case studies and utilizing a national business system lens, we explore a largely underrepresented debate in the literature, namely the nature of change in a specific but critical element of business systems, that is the industrial relations (IR) institutions of the State and the impact of MNCs thereon. Given the critical mass of US investment in Ireland, we examine how US MNCs manage IR in their Irish subsidiaries, how the policies and practices they pursue have impacted on the Irish IR system, and more broadly their role in shaping the host institutional environment. Overall, we conclude that there is some evidence of change in the IR system, change that we trace indirectly to the US MNC sector. Further, the US MNC sector displays evidence of elements of the management of IR that is clearly at odds with Irish traditions. Thus, in these firms we point to the emergence of a hybrid system of the management of IR and the establishment of new traditions more reflective of US business system. [ABSTRACT FROM AUTHOR]

Weedy red rice ( Oryza sativa spontonea) is a persistent and problematic weed of rice culture worldwide. A major hypothesis for the mechanism of production of this weed in South and Southeast Asia is hybridization between cultivated rice ( Oryza sativa) and wild rice ( Oryza rufipogon). However, weedy red rice can often be found outside the range of O. rufipogon leaving questions on the origin and process behind weedy rice infestations. In the USA, weedy red rice was first documented as early as 1846 and has continued to affect rice production areas. In this study, we attempt to identify the origin and population structure of weedy red rice sampled from the USA using both DNA sequence data from a neutral nuclear locus as well as microsatellite genotype data. Results suggest that two major accessions of weedy rice exist, strawhull and blackhull, and these forms may both hybridize with the cultivated rice of the USA, O. sativa japonica. Using population assignment of multilocus genotype signatures with principal component analysis andstructure, an Asian origin is supported for US weedy rice. Additionally, hybridization between strawhull and blackhull varieties was inferred and may present the opportunity for the production of new weedy forms in the future. [ABSTRACT FROM AUTHOR]

Abstract: We conducted a genetic analysis of the extent of hybridization within and outside a contact zone between two North American leopard frogs, Rana blairi and Rana pipiens by comparing distribution patterns of mitochondrial and nuclear haplotypes. The contact zone, located between South Dakota, Nebraska, and Iowa, USA, was previously examined using morphological data in the 1970s, leading to the conclusion that hybridization was rare between R. pipiens and R. blairi. Our genetic analysis of 51 populations (611 samples) shows strong cytonuclear discordance. Mitochondrial–haplotype distribution matches the same pattern as the documented species spatial distributions based on morphology. However, the geographic distribution of the nuclear haplotypes reveals asymmetrical swamping of the R. pipiens nuclear haplotypes by R. blairi haplotypes. Phylogenetic analyses of both mitochondrial and nuclear markers provide strong evidence for the presence of R. blairi–R. pipiens introgression for the nuclear marker. A pattern of mitochondrial isolation with nuclear introgression is extremely unusual, and predicted to occur much less often than the reverse. [Copyright &y& Elsevier]

Natural hybridization plays a critical role in speciation, the maintenance of reproductive isolation, and genetic introgression. While many plant species have hybrid swarms in areas of sympatry, the lack of hybrids among closely related sympatrically distributed species suggests that strong pre- and/or postzygotic barriers exist to hybridization. Gelserniuni sempervirens and G. rankinii (Gelsemiaceae) are sympatrically distributed southeastern sister taxa that have strong postzygotic barriers to hybrid formation and high levels of genetic differentiation. In this study, two sympatric populations in Lowndes County, Georgia were surveyed from 1999-2005 to assess the role of temporal and pollinator isolation as potential prezygotic barriers. The populations had mostly non-overlapping flowering periods in 2003-2005, with significant differences in time of peak flowering and length of flowering. Both species shared a similar community of flower visitors, with the apid bee Habropoda lahoriosa the dominant visitor to both species. A choice experiment found that H. lahoriosa visited both species but preferred G. senlpert'irens. The primary prezygotic barrier is temporal isolation preventing hybridization in spite of the shared pollinators. This study suggests that reliance on a shared pollinator during speciation may limit opportunity for divergent selection on flowering time. [ABSTRACT FROM AUTHOR]

The hybrid sunflower species Helianthus paradoxus inhabits sporadic salt marshes in New Mexico and southwest Texas, USA, whereas its parental species, Helianthus annuus and Helianthus petiolaris, are salt sensitive. Previous studies identified three genomic regions — survivorship quantitative trait loci (QTLs) — that were under strong selection in experimental hybrids transplanted into the natural habitat of H. paradoxus. Here we ask whether these same genomic regions experienced significant selection during the origin and evolution of the natural hybrid, H. paradoxus. This was accomplished by comparing the variability of microsatellites linked to the three survivorship QTLs with those from genomic regions that were neutral in the experimental hybrids. As predicted if one or more selective sweeps had occurred in these regions, microsatellites linked to the survivorship QTLs exhibited a significant reduction in diversity in populations of the natural hybrid species. In contrast, no difference in diversity levels was observed between the two microsatellite classes in parental populations. [ABSTRACT FROM AUTHOR]

In 2005, breast cancer will kill approximately 40,410 women in the U.S., and pancreatic cancer will kill approximately 31,800 men and women in the U.S. Clinical examination and mammography, the currently accepted breast cancer screening methods, miss almost half of breast cancers in women younger than 40 years, approximately one-quarter of cancers in women aged 40-49 years, and one-fifth of cancers in women over 50 years old. Pancreatic cancer progresses rapidly, with only 1% of patients surviving more than 5 years after diagnosis. However, if the disease is diagnosed when it is localized, the 5-year survival is approximately 20%. It would be beneficial to detect breast cancer and pancreatic cancer at the earliest possible stage, when multimodal therapy with surgery, radiotherapy, and chemotherapy have the greatest chance of prolonging survival. Human estrogen receptor-positive breast cancer cells typically display elevated levels of Myc protein due to overexpression of MYC mRNA, elevated cyclin D1 protein due to overexpression of CCND1 mRNA, and elevated insulin-like growth factor 1 receptor (IGF1R) due to overexpression of IGF1R mRNA. We hypothesized that scintigraphic detection of MYC or CCND1 peptide nucleic acid (PNA) probes with an IGF1 peptide loop on the C-terminus, and a Tc-99m-chelator peptide on the N-terminus, could measure levels of MYC or CCND1 mRNA noninvasively in human IGF1Roverexpressing MCF7 breast cancer xenografts in immunocompromised mice. Similarly, human pancreatic cancer cells typically display elevated levels of KRAS mRNA and elevated IGF1R. Hence, we also hypothesized that a KRAS Tc- 99m-chelator PNA-peptide probe could detect overexpression of KRAS mRNA in pancreatic cancer xenografts by scintigraphic imaging, or by positron emission tomography (PET) with a KRAS Cu-64-chelator PNA-peptide. Human MCF7 breast cancer xenografts in immunocompromised mice were imaged scintigraphically 4-24 h after tail-vein administration of MYC or CCND1 Tc- 99m-chelator PNA-peptides, but not after administration of mismatch controls. Similarly, human Panc-1 pancreatic cancer cells xenografts were imaged scintigraphically 4 and 24 h after tail-vein administration of a KRAS Tc-99mchelator PNA-peptide, and AsPC1 xenografts were imaged by PET 4 and 24 h after tail-vein adminstration of a KRAS Cu-64-chelator PNA-peptide. The radioprobes distributed normally to the kidneys, livers, tumors, and other tissues. External molecular imaging of oncogene mRNAs in solid tumors with radiolabel-PNA-peptide chimeras might in the future provide additional genetic characterization of pre-invasive and invasive breast cancers. [ABSTRACT FROM AUTHOR]

DNA microarrays offer the potential for simultaneous detection of many pathogens that are of interest to homeland security, public health, medicine, and veterinary diagnostics. These tools are best suited for detecting the presence or absence of genetic sequences characteristic of specific pathogens, but microarrays are poorly suited for determining pathogen viability, and current methods provide only limited potential for pathogen enumeration. Two basic strategies have been described for pathogen detection: using enzymatic amplification to generate targets for interrogation with a microarray, or using direct interrogation of DNA or RNA without pre-amplification. Multiplex PCR has the advantage of a high degree of sensitivity and specificity, but associated microarrays are necessarily limited in scope. PCR-independent, whole-genome amplification eliminates biases inherent in PCR amplification and can accommodate more extensive microarrays, but assay sensitivity is compromised and these methods are probably of limited use when testing tissue samples. Direct hybridization of DNA or RNA provides the least bias in gene detection, but also the lowest level of analytic sensitivity. Ultimately, cost and limited sample throughput make it unlikely that planar microarrays will play a significant role in future pathogen detection schemes. Alternative microarray formats such as bead arrays, however, may circumvent the cost and throughput limitations and permit us to apply what we have learned from planar microarrays to develop robust pathogen detection systems. Assay validation and sample preparation will continue to be significant challenges for these detection systems. [ABSTRACT FROM AUTHOR]

There are currently no policy guidelines for treating hybrids under the U.S. Endangered Species Act (ESA). We considered the scientific basis for determining whether hybridized populations should be included as part of the westslope cutthroat trout (Oncorhynchus clarki lewisi) unit considered for listing under the ESA. Westslope cutthroat trout are threatened by genomic extinction because of widespread introgressive hybridization with introduced rainbow trout (O. mykiss) and Yellowstone cutthroat trout (O. c. bouvieri). Experimental results suggest that first-generation hybrids between westslope cutthroat trout and rainbow trout have reduced fitness. However, hybridization may spread even when hybrids have severely reduced fitness because the production of hybrids is unidirectional—that is, all the progeny of a hybrid will be hybrids. In addition, heterosis resulting from the sheltering of deleterious recessive alleles in early-generation hybrids may increase the effective rate of introgression. However, such short-term increases in fitness may disrupt important long-term adaptations of native populations. The loss of these adaptations will be difficult to detect because some local adaptations might only be apparent during periodic episodes of extreme environmental conditions, such as winter storms, drought, or fire. Thus, rapid spread of hybridization could result in the loss of local adaptations in native populations of westslope cutthroat trout and decrease their probability of long-term persistence. Protection of populations with some admixture would protect sources of spreading hybridization. Treatment of hybrids in conservation planning depends primarily on the amount of evolutionary divergence between the hybridizing taxa and the geographical extent of introgression. We recommend that only nonhybridized populations be included as westslope cutthroat trout in the unit to be considered for listing. Populations of unknown status should be protected until more information about these populations becomes available. [ABSTRACT FROM AUTHOR]

The channel catfish, Ictalurus punctatus, ♀×blue catfish, Ictalurus furcatus, ♂ F1 hybrid showed increased processing yields over the most commonly cultured catfish, channel catfish, in the US. The F1 hybrid had higher dress-out and fillet percentage (61.1% and 45.7%, respectively) than channel catfish (57.5%, 42.5%), blue catfish (58.9%, 44.4%), F2 hybrid catfish (57.3%, 42.5%), F1×channel catfish (57.3%, 42.7%), F1×blue catfish (58.3%, 42.4%), blue catfish×F1 (58.2%, 43.2%), and channel catfish×F1 (56.8%, 42.1%). Individual heterosis had a strong positive effect on dress-out and fillet percentage. Channel catfish additive genetic effects had a strong negative effect on dress-out and fillet percentage. Females had greater dress-out (58.4% to 57.9%) and fillet percentage (43.6% to 43.0%) than males (P<0.05). Utilization of channel-blue F1 hybrids will increase processing yields and may allow farmers to demand a higher price for their product. [Copyright &y& Elsevier]

Summary 1 Relative fitness of hybrid genotypes will determine the role that hybrids can play in the evolution of a plant species complex. To realistically evaluate hybrid fitness and how environmental variation affects fitness in a long-lived species, all life stages must be considered. 2 We evaluated germination, seedling survival and growth of two Louisiana iris species and their early generation hybrids in several experimental environments created by manipulating light and water levels. 3 Species and hybrids all required similar moist conditions for germination. The proportion of germinated seeds was highest in shade and seedling survival highest in sun. 4 Iris brevicaulis exhibited the lowest germination and seedling survival overall, yet those individuals that survived grew vigorously. Iris fulva had high levels of germination and seedling survival, but yielded the smallest plants at the end of one season of growth. 5 Germination rates, seedling survival and seedling growth of hybrids equalled or exceeded one or both parent species, indicating that hybrids in this system have high relative fitness at seed and seedling stages in several environmental conditions. 6 We conclude that Iris fulva and I. brevicaulis share a common regeneration niche and similar early stage relative fitness with their hybrids. Thus, environment-dependent fitness in this system is due primarily to selection at adult stages. [ABSTRACT FROM AUTHOR]

The Virginia Dale intrusion is a granitic and monzogranitic composite intrusive body at the southern extent of the Sherman batholith in southeastern Wyoming and adjacent areas of Colorado. Within the study area, at the margin of the intrusion, mafic rock (diorite) is commingled with felsic rock (monzogranite) and intermediate rocks. Resulting features include pillows (some with zones of felsic or marie enrichment at their margins), enclaves, mantled quartz grains, and alkali feldspar megacrysts. Intermediate rocks interpreted as hybrids include: (1) granodioritic hybrid; (2) main-phase hybrid; (3) granitoid hybrid; and (4) mafic hybrid. Each of the hybrids shows distinct textural and mixing relations. Mixing and hybridization models were evaluated using major-element, trace-element, and isotopic data. Major-element compositions of the hybrid rocks generally plot along simple mixing lines between mafic and felsic rocks. Incompatible element concentrations of the intermediate rocks are similar to, or greater than, concentrations in the felsic end-member. Trace-element data suggest that the variety of intermediate rocks resulted from chemical diffusion in addition to bulk mixing of heterogeneous end-members. Mafic rocks show a possible differentiation trend, in which the most primitive members are cumulates. The more evolved members show progressive LREE and incompatible element enrichment, growth of a negative europium anomaly (to Eu/Eu* = 0.61), and a correlated decrease in Mg-number (to 0.35). Virginia Dale isotopic data (ε[subNd] = 0 ± 1) are similar to values for the adjacent Sherman batholith, suggesting that both of these bodies formed by partial melting (at 1.43 Ga) of ca. 1.8-Ga crust in the Colorado province. Initial [sup87]Sr/[sup86]Sr values are more heterogeneous, perhaps due to chemical diffusion. [ABSTRACT FROM AUTHOR]

Cultured tetraspores of Petrocelis middendorffii (Ruprecht) Kjellman from Amchitka Island, Alaska, gave a rise to foliose, dioecious gametophytes similar to cultured gametophytes of P. franciscana Setchell & Gardner. A 1:1 ratio male:female gametophytes was obtained. Fertilized female plants produced cystocarps and carpospores that gave rise to crustose plants anatomically similar to field-collected Petrocelis sporophytes. Cultured male gametophytes of P. middendorffii were interfertile with cultured female blades of field-collected Gigartina pacifica Kjellman. Cultured P. middendorffii gametophytes from Amchitka were interfertile with cultured gametophytes of P. franciscana from 2 localities in California. Hybrid carpospores gave rise to crustose sporophytes that have not reproduced. Anatomical comparisons of P. middendorffii from Amchitka with P. franciscana from California showed no important difference in the characters originally used to separate these species. The interfertility of cultured Petrocelis gametophytes from California and Amchitka as well as the similarities of life history and anatomy suggests that a single species is involved. P. franciscana is reduced to a synonym of P. middendorffii. [ABSTRACT FROM AUTHOR]

This study employed nuclear and mitochondrial markers to assess the present-day composition of the population of Agaricus bisporus in coastal California. Favourable weather in the fall, winter and spring of 1990–91 furnished an uncommon opportunity to collect and study field material of the ‘button mushroom’ A. bisporus, a cultivated species, from the region. The previous such season occurred 13 years earlier. Ninety-five nonredundant cultures from field material were prepared and genotypically characterized. These data were combined with data from earlier studies. Multilocus nuclear and mitochondrial genotypes were determined for 123 individuals. Genotypes were compared in pairwise fashion both within the sample and between this sample and others of diverse geographical origin or commercial provenance. Using parametric analysis and cluster analysis of nuclear similarities, and also mitochondrial data, two elements – indigenous and European – were apparent within the sample. This was consistent with our earlier results on a much smaller sample. At least 10 mitochondrial haplotypes (MTs) were present; based on genotypic similarities of associated nuclei, five (or six) MTs were Californian, four were European, and one was ambiguous. Based on MT origins, 54% of the 121 classifiable individuals in California were of European ancestry; natives constituted a minority at 46%. Even in the indigenous Monterey cypress habitat, where 84% of all individuals from California were sampled, non-native A. bisporus appeared to have achieved parity (at 48–49%) with the native population. In all other habitats, which are far more extensive, European individuals outnumbered Californian natives by 4:1. Some evidence of hybridization between the two ancestral groups was found. European strains appear to have been resident in California for approximately one century. The extensive occupancy of the native habitat by non-native germ plasm, the... [ABSTRACT FROM AUTHOR]

The cyprinid fishes Luxilus cornutus and Luxilus chrysocephalus hybridize extensively in a zone extending through the Great Lakes region with extensive introgression of L. cornutus mtDNA occurring in populations of L. chrysocephalus south of the present hybrid zone in Ohio. Western populations of these two species occur adjacent to one another in Missouri but hybridization has never been observed. In order to determine if hybridization has occurred historically in Missouri, allopatric populations of L. chrysocephalus were analysed for mtDNA introgression. Extensive introgression of L. cornutus mtDNA was observed in most populations of L. chrysocephalus in Missouri resulting in the elimination of L. chrysocephalus mtDNA in many populations. Luxilus corn utus mtDNA in L. chrysocephalus is found approximately 300 km south of extant L. cornutus populations in Missouri. Luxi!us chrysocephalus mtDNA was replaced by four unique L. cornutus mtDNA haplotypes, with one particular haplotype becoming fixed in several L. chrysocephalus populations. The pattern of introgression suggests that historically L. cornutus occupied a more southern distribution in Missouri bringing it into contact with western populations of L. chrysocephalus and resulting in a hybrid zone. [ABSTRACT FROM AUTHOR]

Wild germplasm can be classified as the raw material essential for crop improvement. Introgression of wild germplasm is normally used in breeding to increase crop quality or resilience to evolving biotic and abiotic threats. Here, we explore the potential of introgressing Vaccinium elliottii into commercial blueberry germplasm. Vaccinium elliottii is a wild diploid blueberry species endemic to the southeastern United States that possesses highly desirable and economically important traits for blueberry breeding such as: short bloom to ripe period, adaptation to upland sandy soils, disease resistance, firmness, and pleasant flavor. To examine the potential of hybridization, we evaluated populations of interspecific hybrids across multiple stages of breeding (i.e., F1, F2, and backcrosses) in two crop seasons. We used our extensive pedigree data to generate breeding values for pre-breeding blueberry hybrid populations. Hybrid performance was evaluated considering fitness (i.e., plant vigor and plant height) in addition to evaluating six fruit-quality and marketable-related traits (i.e., size, firmness, acidity, soluble solids, weight, and yield). Overall, F2 and backcrosses rapidly achieved market thresholds, presenting values not significantly different from commercial blueberry germplasm. Our results confirmed the potential of exploiting the high genetic variability contained in V. elliottii for interspecific hybridization. Additionally, we developed germplasm resources that can be further evaluated and utilized in the breeding process, advancing selections for fruit quality and environmental adaptation. [ABSTRACT FROM AUTHOR]

Thirteen newly developed tri- and tetranucleotide repeat microsatellite markers were developed for Lahontan cutthroat trout ( Oncorhynchus clarki henshawi), a threatened subspecies endemic to the Lahontan hydrographic basin in the western USA. These loci are highly polymorphic with five to 30 alleles per locus and observed heterozygosities ranging from 0.4 to 0.7. Cross-species amplification of these markers was most successful in the closely related rainbow trout, Oncorhynchus mykiss, with only three loci amplifying in brown trout, Salmo trutta. Nonoverlapping allelic distributions for many of these loci among the six salmonid species screened suggest these markers may be useful for hybrid determination. [ABSTRACT FROM AUTHOR]

• Most of the natural geographical distribution of Nulembo lutea was sampled. • Low level of genetic diversity was revealed in American lotus populations. • High genetic differentiation and strong population structure was observed. • Low level of gene flow among the genetic pools was revealed. American lotus (Nelumbo lutea Willd.) is a popular plant with ornamental, medicinal, and culinary value. Studies related to the genetic diversity and population structure of N. lutea are limited. We sampled 326 individuals from 19 populations of wild N. lutea across its distribution range in the USA and genotyped them using 12 microsatellite markers. A total of 274 alleles were amplified by 12 microsatellites with a mean of 22.83. We observed a low level of genetic diversity for American lotus (A e = 2.40 and H E = 0.459) in the USA. The analysis of molecular variance (AMOVA) exhibited closer variation among populations (42.00%) than within populations (58.00%) of N. lutea, with strong genetic differentiation observed (F ST = 0.419). There was no significant correlation between genetic and geographic distances. The Bayesian analysis and neighbor-joining dendrogram displayed strong population structure. A very low level of historical gene flow (N M = 0.073) was observed among the populations. Fourteen of the 19 populations showed a demographic bottleneck, indicating the vulnerability of the American lotus populations. We thus proposed priority population sites for the conservation of N. lutea via both ex-situ and in-situ techniques. [ABSTRACT FROM AUTHOR]

As humans cause the redistribution of species ranges, hybridization between previously allopatric species is on the rise. Such hybridization can have complex effects on overall fitness of native species as new allelic combinations are tested. Widespread species introductions provide a unique opportunity to study selection on introgressed alleles in independent, replicated populations. We examined selection on alleles that repeatedly introgressed from introduced rainbow trout (Oncorhynchus mykiss) into native westslope cutthroat trout (Oncorhynchus clarkii lewisi) populations in western Canada. We found that the degree of introgression of individual single nucleotide polymorphisms from the invasive species into the native is correlated between independent watersheds. A number of rainbow trout alleles have repeatedly swept to high frequency in native populations, suggesting parallel adaptive advantages. Using simulations, we estimated large selection coefficients up to 0.05 favoring several rainbow trout alleles in the native background. Although previous studies have found reduced hybrid fitness and genome-wide resistance to introgression in westslope cutthroat trout, our results suggest that some introduced genomic regions are strongly favored by selection. Our study demonstrates the utility of replicated introductions as case studies for understanding parallel adaptation and the interactions between selection and introgression across the genome. We suggest that understanding this variation, including consideration of beneficial alleles, can inform management strategies for hybridizing species., (© 2019 John Wiley & Sons Ltd.)

In hybrid zones occurring in marginal environments, adaptive introgression from one species into the genomic background of another may constitute a mechanism facilitating adaptation at range limits. Although recent studies have improved our understanding of adaptive introgression in widely distributed tree species, little is known about the dynamics of this process in populations at the margins of species ranges. We investigated the extent of introgression between three species of the genus Populus sect. Tacamahaca (P. balsamifera, P. angustifolia and P. trichocarpa) at the margins of their distributions in the Rocky Mountain region of the United States and Canada. Using genotyping by sequencing (GBS), we analysed ~ 83,000 single nucleotide polymorphisms genotyped in 296 individuals from 29 allopatric and sympatric populations of the three species. We found a trispecies hybrid complex present throughout the zone of range overlap, including early as well as advanced generation backcross hybrids, indicating recurrent gene flow in this hybrid complex. Using genomic cline analysis, we found evidence of non-neutral patterns of introgression at 23% of loci in hybrids, of which 47% and 8% represented excess ancestry from P. angustifolia and P. balsamifera, respectively. Gene ontology analysis suggested these genomic regions were enriched for genes associated with photoperiodic regulation, metal ion transport, maintenance of redox homeostasis and cell wall metabolites involved in regulation of seasonal dormancy. Our study demonstrates the role of adaptive introgression in a multispecies hybrid complex in range-edge populations and has implications for understanding the evolutionary dynamics of adaptation in hybrid zones, especially at the margins of species distributions., (© 2018 John Wiley & Sons Ltd.)

Hybridization among conspecifics in native and introduced habitats has important implications for biological invasions in new ecosystems. Bighead (Hypophthalmichthys nobilis) and silver carp (H. molitrix) are genetically isolated and occur in sympatry within their native range. Following their introduction to North America, however, introgressant hybrids have been reported throughout their expanded range within the Mississippi River Basin (MRB). The extent of introgression, both spatially and generationally, is largely unknown. Therefore, we examined mixed-species populations from across the MRB to characterize the extent of interspecific gene flow. We assayed 2798 individuals from nine locations with a suite of species-diagnostic SNPs (57 nuclear and one mitochondrial). Forty-four per cent (n = 1244) of individuals displayed hybrid genotypes. Moreover, the composition of hybrid genotypes varied among locations and represented complex hybrid swarms with multiple generations of gene flow. Introgressive hybrids were identified from all locations, were bidirectional and followed a bimodal distribution consisting primarily of parental or parental-like genotypes and phenotypes. All described hybrid categories were present among individuals from 1999 to 2008, with parents and later-generation backcrosses representing the largest proportion of individuals among years. Our mitochondrial SNP (COII), tested on a subset of 730 individuals, revealed a silver carp maternal bias in 13 of 21 (62%) F1 hybrids, in all silver carp backcrosses, and maintained throughout many of the bighead carp backcrosses. The application of this suite of diagnostic markers and the spatial coverage permits a deeper examination of the complexity in hybrid swarms between two invasive, introduced species., (© 2015 John Wiley & Sons Ltd.)

Detailed information about the geographic distribution of genetic and genomic variation is necessary to better understand the organization and structure of biological diversity. In particular, spatial isolation within species and hybridization between them can blur species boundaries and create evolutionary relationships that are inconsistent with a strictly bifurcating tree model. Here, we analyse genome-wide DNA sequence and genetic ancestry variation in Lycaeides butterflies to quantify the effects of admixture and spatial isolation on how biological diversity is organized in this group. We document geographically widespread and pervasive historical admixture, with more restricted recent hybridization. This includes evidence supporting previously known and unknown instances of admixture. The genome composition of admixed individuals varies much more among than within populations, and tree- and genetic ancestry-based analyses indicate that multiple distinct admixed lineages or populations exist. We find that most genetic variants in Lycaeides are rare (minor allele frequency <0.5%). Because the spatial and taxonomic distributions of alleles reflect demographic and selective processes since mutation, rare alleles, which are presumably younger than common alleles, were spatially and taxonomically restricted compared with common variants. Thus, we show patterns of genetic variation in this group are multifaceted, and we argue that this complexity challenges simplistic notions concerning the organization of biological diversity into discrete, easily delineated and hierarchically structured entities., (© 2014 John Wiley & Sons Ltd.)

Pleistocene climate cycles and glaciations had profound impacts on taxon diversification in the Boreal Forest Biome. Using population genetic analyses with multilocus data, we examined diversification, isolation, and hybridization in two sibling species of tree squirrels (Tamiasciurus douglasii and Tamiasciurus hudsonicus) with special attention to the geographically and genetically enigmatic population of T. hudsonicus on Vancouver Island, Canada. The two species differentiated only about 500,000 years ago, in the Late Pleistocene. The island population is phylogenetically nested within T. hudsonicus according to our nuclear analysis but within T. douglasii according to mitochondrial DNA. This conflict is more likely due to historical hybridization than to incomplete lineage sorting, and it appears that bidirectional gene flow occurred between the island population and both species on the mainland. This interpretation of our genetic analyses is consistent with our bioclimatic modeling, which demonstrates that both species were able to occupy this region throughout the Late Pleistocene. The divergence of the island population 40,000 years ago suggests that tree squirrels persisted in a refugium on Vancouver Island at the last glacial maximum, 20,000 years ago. Our observations demonstrate how Pleistocene climate change and habitat shifts have created incipient divergence in the presence of gene flow. Sequence data have been archived in GenBank—accession numbers: KF882736–KF885216., (© 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.)