A complete history of the establishment of Japanese sika deer on the Delmarva Peninsula: 100 years post-introduction

While many non-native species immediately express their negative qualities which encourage their management (even attempted eradication), some have long lag periods before the population begins to grow out of control. Sika deer have been problematic in many places where they were introduced as novelties or games species through hybridization or aggressive interactions with native deer. In attempt to better manage these species we need to know their native ecosystem. We provide evidence through summarized literature of the manner in which sika deer arrived on Delmarva from Yakushima Island in Japan via a multi-generational stopover in the United Kingdom. We also add morphological and genetic support that confirm the origins and help describe the path of introduction of sika deer to Maryland. We also summarize the growth and change in population size(s) over the last 100 years. This historic understanding is an essential part of coping with the persistent growth of a large, aggressive herbivore that is currently being managed as a game species. We summarize the possible impacts of sika deer including the displacement of native white-tailed deer. The management of this species needs to be carefully observed as they continue to spread throughout the critical saltmarsh of the Delmarva Peninsula.     

Bayesian inference of a complex invasion history revealed by nuclear and chloroplast genetic diversity in the colonizing plant,Silene latifolia

Species invading new ranges are subject to a series of demographic events that can strongly shape genetic diversity. Describing this demographic history is important for understanding where invasive species come from and how they spread, and is critical to testing hypotheses of postinvasion adaptation. Here, we analyse nuclear and chloroplast genetic diversity to study the invasion history of the widespread colonizing weed, Silene latifolia (Caryophyllaceae). Bayesian clustering and PCA revealed strong population structure in the native range of Europe, and although genotypes from multiple native sources were present in the introduced range of North America, the spatial distribution of genetic variance was dramatically reorganized. Using approximate Bayesian computation (ABC), we compared support for different invasion scenarios, including the number and size of independent introduction events and the amount of admixture occurring between sources of introduced genotypes. Our results supported independent introductions into eastern and western North America, with the latter forming a bridgehead for a secondary invasion into the Great Lakes region of central North America. Despite small estimated founder population sizes, the duration of the demographic bottleneck after the initial introduction appeared extremely short‐lived. This pattern of repeated colonization and rapid expansion has effectively eroded the strong population structure and cytonuclear associations present in Europe, but has retained overall high genetic diversity since invasion. Our results highlight the flexibility of the ABC approach for constructing a narrative of the demographic history of species invasions and provide baseline for future studies of evolutionary changes in introduced S. latifolia populations.     

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

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

Genetic differentiation between introduced Central European sika and source populations in Japan: effects of isolation and demographic events

Japanese sika deer (Cervus nippon nippon) were introduced at the turn of nineteenth and twentieth century to many countries in Eurasia, North America and Australasia. Subsequently, free-living invasive populations have become established in several countries, including the Czech Republic, where the expanding sika population causes serious problems through overgrazing, damage through browsing and through competition and hybridisation with native red deer. 122 Japanese and 221 Czech samples were used to examine the genetic diversity, genetic structure, and the level of genetic differentiation between native populations and those introduced to the Czech Republic. Analyses of 22 microsatellite loci revealed, for both countries, evidence of isolation by distance and clear sub-structuring of populations, different from patterns previously revealed by mtDNA markers. The high number of private alleles (58 within the Czech Republic and 84 within Japan), the Fst values, factorial correspondence analysis and Bayesian clustering support a high level of divergence between the source and introduced populations. Genetic variability was generally low due to recent demographic events (founder effect in the Czech population, bottlenecks in Japanese populations); however, the values of expected heterozygosity differed greatly between subpopulations and were not the lowest in the introduced Czech populations. Multiple introductions, rapid population growth, and possible hybridisation with red deer seem to have helped the successful expansion of sika within the Czech Republic. The results also indicate that male-mediated gene flow and human-mediated translocations have significantly influenced the current genetic structure of native sika populations in Japan.     

Molecular evidence for a founder effect in invasive house finch (Carpodacus mexicanus) populations experiencing an emergent disease epidemic

The impact of founder events on levels of genetic variation in natural populations remains a topic of significant interest. Well-documented introductions provide a valuable opportunity to examine how founder events influence genetic diversity in invasive species. House finches (Carpodacus mexicanus) are passerine birds native to western North America, with the large eastern North American population derived from a small number of captive individuals released in the 1940s. Previous comparisons using amplified fragment length polymorphism (AFLP) markers found equivalent levels of diversity in eastern and western populations, suggesting that any genetic effects of the founder event were ameliorated by the rapid growth of the newly established population. We used an alternative marker system, 10 highly polymorphic microsatellites, to compare levels of genetic diversity between four native and five introduced house finch populations. In contrast to the AFLP comparisons, we found significantly lower allelic richness and heterozygosity in introduced populations across all loci. Three out of five introduced populations showed significant reductions in the ratio of the number of alleles to the allele size range, a within-population characteristic of recent bottlenecks. Finally, native and introduced populations showed significant pairwise differences in allele frequencies in every case, with stronger isolation by distance within the introduced than native range. Overall, our results provide compelling molecular evidence for a founder effect during the introduction of eastern house finches that reduced diversity levels at polymorphic microsatellite loci and may have contributed to the emergence of the Mycoplasma epidemic which recently swept the eastern range of this species.     

Bottleneck effects on the sika deer Cervus nippon population in Hokkaido, revealed by ancient DNA analysis

The population size of the sika deer Cervus nippon on Hokkaido Island of Japan had been remarkably reduced because of heavy hunting pressure since the beginning of Meiji Period and effects of heavy snow in 1879 and 1881. After that, the number of sika deer in Hokkaido has increased gradually due to the protection by the Hokkaido government. In the present study, in order to investigate the bottleneck effects, we analyzed ancient mitochondrial DNA (mtDNA) on sika deer bones excavated from archaeological sites just before Meiji Period. On 86 of 113 bones from 13 archaeological sites of Ainu Culture Period (17-19th centuries), 602 base-pair fragments of the mtDNA control region were successfully sequenced. Consequently, we found three new haplotypes (g-, h- and i-types) which had not been identified in modern sika deer. In addition, four haplotypes (a-, b-, c- and d-types) identified from modern sika deer were also found in the archaeological deer. The new haplotypes and previously reported hapoltypes from sika deer of Hokkaido were phylogenetically much closer to each other, compared with those of modern sika deer from Honshu, Kyushu and the Chinese continent. Geographical distribution patterns of haplotypes of the ancient population were different from those of the modern population in Hokkaido. Our findings indicated that their genetic diversity was reduced through the bottleneck and that population structures of sika deer were changed widely in Hokkaido due to genetic drift.     

Absence of founder effect and evidence for adaptive divergence in a recently introduced insular population of white‐tailed deer (Odocoileus virginianus)

Islands are generally colonized by few individuals which could lead to a founder effect causing loss of genetic diversity and rapid divergence by strong genetic drift. Insular conditions can also induce new selective pressures on populations. Here, we investigated the extent of genetic differentiation within a white‐tailed deer (Odocoileus virginianus) population introduced on an island and its differentiation with its source mainland population. In response to their novel environmental conditions, introduced deer changed phenotypically from mainland individuals, therefore we investigated the genetic bases of the morphological differentiation. The study was conducted on Anticosti Island (Québec, Canada) where 220 individuals were introduced 120 years ago, resulting in a population size over 160,000 individuals. We used genotyping‐by‐sequencing (GBS) to generate 8,518 filtered high‐quality SNPs and compared patterns of genetic diversity and differentiation between the continental and Anticosti Island populations. Clustering analyses indicated a single panmictic island population and no sign of isolation by distance. Our results revealed a weak, albeit highly significant, genetic differentiation between the Anticosti Island population and its source population (mean F_ST = 0.005), which allowed a population assignment success of 93%. Also, the high genetic diversity maintained in the introduced population supports the absence of a strong founder effect due to the large number of founders followed by rapid population growth. We further used a polygenic approach to assess the genetic bases of the divergent phenotypical traits between insular and continental populations. We found loci related to muscular function and lipid metabolism, which suggested that these could be involved in local adaptation on Anticosti Island. We discuss these results in a harvest management context.     

Widespread hybridization in the introduced hog deer population of Victoria,Australia, and its implications for conservation

In Australia, many species have been introduced that have since undergone drastic declines in their native range. One species of note is the hog deer (Axis porcinus) which was introduced in the 1860s to Victoria, Australia, and has since become endangered in its native range throughout South‐East Asia. There is increased interest in using non‐native populations as a source for genetic rescue; however, considerations need to be made of the genetic suitability of the non‐native population. Three mitochondrial markers and two nuclear markers were sequenced to assess the genetic variation of the Victorian population of hog deer, which identified that the Victorian population has hybrid origins with the closely related chital (Axis axis), a species that is no longer present in the wild in Victoria. In addition, the mitochondrial D‐loop region within the Victorian hog deer is monomorphic, demonstrating that mitochondrial genetic diversity is very low within this population. This study is the first to report of long‐term persistence of hog deer and chital hybrids in a wild setting, and the continual survival of this population suggests that hybrids of these two species are fertile. Despite the newly discovered hybrid status in Victorian hog deer, this population may still be beneficial for future translocations within the native range. However, more in‐depth analysis of genetic diversity within the Victorian hog deer population and investigation of hybridization rates within the native range are necessary before translocations are attempted.     

The population genetics of a biological control introduction: mitochondrial DNA and microsatellie variation in native and introduced populations of Aphidus ervi, a parisitoid wasp

Introductions of biological control agents may cause bottlenecks in population size despite efforts to avoid them. We examined the population genetics of Aphidius ervi (Hymenoptera: Braconidae), a parasitoid that was introduced to North America from Western Europe in 1959 to control pea aphids. To explore the phylogeographical relationships of A. ervi we sequenced 1249 bp of mitochondrial DNA (mtDNA) from 27 individuals from the native range and 51 individuals from the introduced range. Most individuals from Western Europe, the Middle East and North America shared one of two common haplotypes, consistent with the known history of the introduction. However, some A. ervi from the Pacific Northwest have a haplotype that is most similar to haplotypes found in Japan, raising the possibility of a second accidental introduction. To examine population structure and assess whether a bottleneck occurred upon introduction to North America, we assayed variation at 5 microsatellite loci in 62 individuals from 2 native populations and 230 individuals from 6 introduced populations. Introduced samples had fewer rare alleles than native samples (F1,34 = 13.5, P = 0.0008), but heterozygosity did not differ significantly. These results suggest that a mild bottleneck occurred in spite of the introduction of over 1000 individuals. Using a hierarchical Bayesian approach, the founding population size was estimated to be 245 individuals. amova showed significant genetic differentiation between the European and North American samples, and a Bayesian assignment approach clustered individuals into four groups, with most European individuals in one group and most North American individuals in the other three. These results highlight that genetic changes are associated with founder events in rapidly growing natural populations, even when the founding population size is relatively large.     

Demographic history of a recent invasion of house mice on the isolated Island of Gough

Island populations provide natural laboratories for studying key contributors to evolutionary change, including natural selection, population size and the colonization of new environments. The demographic histories of island populations can be reconstructed from patterns of genetic diversity. House mice (Mus musculus) inhabit islands throughout the globe, making them an attractive system for studying island colonization from a genetic perspective. Gough Island, in the central South Atlantic Ocean, is one of the remotest islands in the world. House mice were introduced to Gough Island by sealers during the 19th century and display unusual phenotypes, including exceptionally large body size and carnivorous feeding behaviour. We describe genetic variation in Gough Island mice using mitochondrial sequences, nuclear sequences and microsatellites. Phylogenetic analysis of mitochondrial sequences suggested that Gough Island mice belong to Mus musculus domesticus, with the maternal lineage possibly originating in England or France. Cluster analyses of microsatellites revealed genetic membership for Gough Island mice in multiple coastal populations in Western Europe, suggesting admixed ancestry. Gough Island mice showed substantial reductions in mitochondrial and nuclear sequence variation and weak reductions in microsatellite diversity compared with Western European populations, consistent with a population bottleneck. Approximate Bayesian computation (ABC) estimated that mice recently colonized Gough Island (~100 years ago) and experienced a 98% reduction in population size followed by a rapid expansion. Our results indicate that the unusual phenotypes of Gough Island mice evolved rapidly, positioning these mice as useful models for understanding rapid phenotypic evolution.     

Founder events predict changes in genetic diversity during human‐mediated range expansions

Intentional or accidental introduction of species to new locations is predicted to result in loss of genetic variation and increase the likelihood of inbreeding, thus reducing population viability and evolutionary potential. However, multiple introductions and large founder numbers can prevent loss of genetic diversity and may therefore facilitate establishment success and range expansion. Based on a meta‐analysis of 119 introductions of 85 species of plants and animals, we here show a quantitative effect of founding history on genetic diversity in introduced populations. Both introduction of large number of individuals and multiple introduction events significantly contribute to maintaining or even increasing genetic diversity in introduced populations. The most consistent loss of genetic diversity is seen in insects and mammals, whereas introduced plant populations tend to have higher genetic variation than native populations. However, loss or gain of genetic diversity does not explain variation in the extent to which plant or animal populations become invasive outside of their native range. These results provide strong support for predictions from population genetics theory with respect to patterns of genetic diversity in introduced populations, but suggest that invasiveness is not limited by genetic bottlenecks.     

Genetic signature of a range expansion and leap‐frog event after the recent invasion of Europe by the grapevine downy mildew pathogen Plasmopara viticola

Biologic invasions can have important ecological, economic and social consequences, particularly when they involve the introduction and spread of plant invasive pathogens, as they can threaten natural ecosystems and jeopardize the production of human food. Examples include the grapevine downy mildew, caused by the oomycete Plasmopara viticola, an invasive species native to North America, introduced into Europe in the 1870s. We investigated the introduction and spread of this invasive pathogen, by analysing its genetic structure and diversity in a large sample from European vineyards. Populations of P. viticola across Europe displayed little genetic diversity, consistent with the occurrence of a bottleneck at the time of introduction. Bayesian coalescent analyses revealed a clear population expansion signal in the genetic data. We detected a weak, but significant, continental‐wide population structure, with two geographically and genetically distinct clusters in Western and Eastern European vineyards. Approximate Bayesian computation, analyses of clines of genetic diversity and of isolation‐by‐distance patterns provided evidence for a wave of colonization moving in an easterly direction across Europe. This is consistent with historical reports, first mentioning the introduction of the disease in Bordeaux vineyards (France) and sub‐sequently documenting its rapid spread across Europe. This initial introduction in the west was probably followed by a ‘leap‐frog’ event into Eastern Europe, leading to the formation of the two genetic clusters we detected. This study shows that recent population genetics methods within the Bayesian and coalescence frameworks are extremely powerful for increasing our understanding of pathogen population dynamics and invasion histories.     

Implications of social dominance and multiple paternity for the genetic diversity of a captive-bred reptile population (tuatara)

Captive breeding is an integral part of many species recovery plans. Knowledge of the genetic mating system is essential for effective management of captive stocks and release groups, and can help to predict patterns of genetic diversity in reintroduced populations. Here we investigate the poorly understood mating system of a threatened, ancient reptile (tuatara) on Little Barrier Island, New Zealand and discuss its impact on the genetic diversity. This biologically significant population was thought to be extinct, due to introduced predators, until 8 adults (4 males, 4 females) were rediscovered in 1991/92. We genotyped these adults and their 121 captively-bred offspring, hatched between 1994 to 2005, at five microsatellite loci. Multiple paternity was found in 18.8% of clutches. Male variance in reproductive success was high with one male dominating mating (77.5% of offspring sired) and one male completely restricted from mating. Little Barrier Island tuatara, although clearly having undergone a demographic bottleneck, are retaining relatively high levels of remnant genetic diversity which may be complemented by the presence of multiple paternity. High variance in reproductive success has decreased the effective size of this population to approximately 4 individuals. Manipulation to equalize founder representation was not successful, and the mating system has thus had a large impact on the genetic diversity of this recovering population. Although population growth has been successful, in the absence of migrants this population is likely at risk of future inbreeding and genetic bottleneck.     

The origin and genetic variability of the Czech sika deer population

Sika deer (Cervus nippon), native to Asia, formed two well-established free-living populations in the Czech Republic over the last century and continue to spread. Sika are also maintained in a large number of enclosures; these continue to introduce new individuals from the places of its origin as well as from other European countries. Despite extensive research into the morphology and ethology of the Czech sika deer, conducted over the last three decades, no study using genetic methods has been done. This study aimed to determine the genetic variability and the geographic origin of the Czech sika deer population. Two mitochondrial markers, the cytochrome b and the control region were analyzed in this study. Analysis of the two markers confirmed that the founder individuals of the Czech population originated from both native island (Japanese Islands) and native mainland (Far East Russia) populations. Results showed that the genetic variability of the Czech sika deer population is lower than the variability of the native Japanese population, but higher than that of the sampled part of the native Russian population. Also, the genetic variability was found to be higher within the samples from enclosures.     

SNPs across time and space: population genomic signatures of founder events and epizootics in the House Finch (Haemorhous mexicanus)

Identifying genomic signatures of natural selection can be challenging against a background of demographic changes such as bottlenecks and population expansions. Here, we disentangle the effects of demography from selection in the House Finch (Haemorhous mexicanus) using samples collected before and after a pathogen‐induced selection event. Using ddRADseq, we genotyped over 18,000 SNPs across the genome in native pre‐epizootic western US birds, introduced birds from Hawaii and the eastern United States, post‐epizootic eastern birds, and western birds sampled across a similar time span. We found 14% and 7% reductions in nucleotide diversity, respectively, in Hawaiian and pre‐epizootic eastern birds relative to pre‐epizootic western birds, as well as elevated levels of linkage disequilibrium and other signatures of founder events. Despite finding numerous significant frequency shifts (outlier loci) between pre‐epizootic native and introduced populations, we found no signal of reduced genetic diversity, elevated linkage disequilibrium, or outlier loci as a result of the epizootic. Simulations demonstrate that the proportion of outliers associated with founder events could be explained by genetic drift. This rare view of genetic evolution across time in an invasive species provides direct evidence that demographic shifts like founder events have genetic consequences more widespread across the genome than natural selection.     

Low genetic and morphological differentiation between an introduced population of dunnocks in New Zealand and an ancestral population in England

Species invasions and exotic species introductions can be considered as ??unplanned experiments??, which help us to understand the evolution of organisms. In this study, we investigated whether an exotic bird species, the dunnock (Prunella modularis), has diverged genetically and morphologically from its native source population (Cambridge, England) after introduction into a new environment (Dunedin, South Island of New Zealand; exotic population). We used a set of microsatellite markers and three morphological traits to quantify the divergence between these two populations. We quantified neutral genotypic differentiation between the populations, and also used an individual-based Bayesian clustering method to assess genetic structure. We compared morphological divergence using univariate and principal components analyses. We found that individuals from the Dunedin population are genetically distinct from the Cambridge population, but levels of differentiation are very low. Overall within-population levels of genetic diversity are low compared to other bird species, and effective population sizes are small; indicating that the native population probably has a historically low level of genetic diversity, and that the introduced population retained most of that diversity after its introduction into New Zealand. We found little evidence of morphological divergence, and the evolutionary rate of change in these traits is below the average for other taxa. Our study adds support to the growing literature showing that invasive species maintain most of their initial genetic diversity after multiple founder events, even when population size is severely reduced. Moreover, our morphological data indicate slow evolutionary rates in species introduced to similar habitats.     

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

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

Comparing the genetics of wild and captive populations of White‐headed Ducks Oxyura leucocephala: consequences for recovery programmes

The White‐headed Duck is a globally threatened species historically recorded from Spain in the west to China in the east. It has suffered major population declines, local extinctions and range fragmentation. Several projects have attempted to reintroduce captive‐bred birds into parts of the former range in Europe, but with little success. Two captive stocks currently exist, one originating from Pakistan in 1968 and the other originating from Spain in 1982. This study compares the suitability of these captive stocks for specific reintroduction projects by using 11 microsatellite markers and mtDNA control region sequences to assess genetic differences between captive populations and wild birds from Spain and Greece. No significant population structure was found and all microsatellite alleles recorded in captive birds originating from Pakistan were also observed in the wild Spanish population. A higher diversity of alleles was observed in wild birds from Greece than from Spain, probably due to the effects of a strong bottleneck experienced in Spain in the 1970s. Compared with wild populations, both captive stocks have suffered a significant loss of diversity in microsatellites and mitochondrial DNA owing to founder effects and/or genetic drift, and therefore may not be well suited for release programmes. We recommend the development of a more diverse captive breeding programme based on birds taken from different areas of the range, in particular by supplementing the Spanish population with birds from North Africa. Our study shows the value of molecular tools in developing conservation programmes for threatened bird species and has implications for the design of recovery programmes.     

Analysis of founder representation in pedigrees: Founder equivalents and founder genome equivalents

The concepts of “founder equivalent” and “founder genome equivalent” are introduced to facilitate analysis of the founding stocks of captive or other populations for which pedigrees are available. The founder equivalents of a population are the number of equally contributing founders that would be expected to produce the same genetic diversity as in the population under study. Unequal genetic contributions by founders decrease the founder equivalents, portend greater inbreeding in future generations than would be necessary, and reflect a greater loss of the genetic diversity initially present in the founders. The number of founder genome equivalents of a population is that number of equally contributing founders with no random loss of founder alleles in descendants that would be expected to produce the same genetic diversity as in the population under study. The number of founder genome equivalents is approximately that number of wild-caught animals that would be needed to obtain the same amount of genetic diversity as is in the descendant captive population. Founder equivalents and founder genome equivalents allow comparison of the genetic merits of adding new wild-caught stock vs. further equalizing founder representations in a captive population.     

Influence of invasion history on rapid morphological divergence across island populations of an exotic bird

There is increasing evidence that exotic populations may rapidly differentiate from those in their native range and that differences also arise among populations within the exotic range. Using morphological and DNA‐based analyses, we document the extent of trait divergence among native North American and exotic Hawaiian populations of northern cardinal (Cardinalis cardinalis). Furthermore, using a combination of historical records and DNA‐based analyses, we evaluate the role of founder effects in producing observed trait differences. We measured and compared key morphological traits across northern cardinal populations in the native and exotic ranges to assess whether trait divergence across the Hawaiian Islands, where this species was introduced between 1929 and 1931, reflected observed variation across native phylogeographic clades in its native North America. We used and added to prior phylogenetic analyses based on a mitochondrial locus to identify the most likely native source clade(s) for the Hawaiian cardinal populations. We then used Approximate Bayesian Computation (ABC) to evaluate the role of founder effects in producing the observed differences in body size and bill morphology across native and exotic populations. We found cardinal populations on the Hawaiian Islands had morphological traits that diverged substantially across islands and overlapped the trait space of all measured native North American clades. The phylogeographic analysis identified the eastern North American clade (C. cardinalis cardinalis) as the most likely and sole native source for all the Hawaiian cardinal populations. The ABC analyses supported written accounts of the cardinal's introduction that indicate the original 300 cardinals shipped to Hawaii were simultaneously and evenly released across Hawaii, Kauai, and Oahu. Populations on each island likely experienced bottlenecks followed by expansion, with cardinals from the island of Hawaii eventually colonizing Maui unaided. Overall, our results suggest that founder effects had limited impact on morphological trait divergence of exotic cardinal populations in the Hawaiian archipelago, which instead reflect postintroduction events.