Native Range Populations Research Articles

Genetic variation of Spartina alterniflora intentionally introduced to China

Spread of smooth cordgrass (Spartina alterniflora) in China is an exceptional example of unanticipated outcomes arising from intentional introductions. It has been proposed that in China, management strategies used to establish S. alterniflora inadvertently promoted evolutionary outcomes that have contributed to other Spartina invasions. In this study, we assessed whether S. alterniflora in China exhibits genetic signatures of mechanisms known to promote invasion success, including large founding populations, evolved self-fertility, ‘superior source ecotypes’, and post-introduction admixture. This involved comparing microsatellite genotype and chloroplast haplotype variation among Chinese populations to other invasive S. alterniflora populations as well as native range populations, inclusive of samples from all reported source areas. We found distinct signatures of source population contributions to Chinese populations, as well as evidence of post-introduction admixture, and no evidence of limitations from a genetic bottleneck. Measures of inbreeding were well below what has been found in other non-native populations that have evolved self-fertility. Differences in genetic diversity among sites were similar to latitudinal patterns in the native range, but could be attributable to introduction history. Comparisons to other invasive populations indicate that a combination of common and idiosyncratic processes have contributed to the success of S. alterniflora in China and elsewhere, with intentional introductions promoting mechanisms that accelerate rates of spread and widespread invasion.

Nitrogen‐fixing bacterial communities in invasive legume nodules and associated soils are similar across introduced and native range populations in Australia

AbstractAimUnderstanding the interactions between invasive legumes and soil biota in both native and introduced ranges could assist in managing biological invasions. We analysed the diversity of putative nitrogen‐fixing bacteria (NFB, i.e. nifH gene present) associated with five invasive legumes, four Acacia spp. and a sister taxon Paraserianthes lophantha in introduced and native range populations in Australia. We predicted that, because these host species are widely distributed, they are likely to encounter different nitrogen‐fixing bacterial communities in soils and nodules across their introduced and native ranges.LocationAustralia.MethodsNifH genes were amplified from rhizosphere soils collected from beneath each species (multiple populations) within their native and introduced range and directly from nodules collected from plants previously grown in the glasshouse using field‐collected soil as inoculum. NifH gene sequences from soils and nodules were 454 pyrosequenced and assigned to taxonomic groups based on nifH consensus taxonomy.ResultsWe found no difference in the NFB community of soils or nodules between native and introduced ranges across the five species, suggesting that these legumes encounter similar NFB communities in soils across Australia. Bradyrhizobium was the most abundant rhizobial genus present in both soils and nodules. Bradyrhizobium species found in nodules were significantly different across the ranges for A. longifolia.Main conclusionsThe results indicate that these invasive legumes have similar nitrogen‐fixing bacterial communities in their rhizosphere and nodules across Australia, with the exception of A. longifolia. This species has diverse Bradyrhizobium genotypes in its nodules suggesting that A. longifolia may be a more generalist host compared to the other four legumes. Thus, it is unlikely that the invasive success of these legumes is constrained by the absence of suitable bacterial symbionts in soil. Better knowledge of legume–soil interactions could facilitate more informed and effective management of invasive legumes in their introduced ranges in Australia and elsewhere.

Geographic independence and phylogenetic diversity of red shiner introductions

Identifying areas at risk of invasion can be difficult when the distribution of a non-native species encompasses geographically disjunct regions. Understanding genealogical relationships among native and non-native populations can clarify the origins of fragmented distributions, which in turn can clarify how fast and far a non-native species may spread. We evaluated genetic variation across the native and invasive ranges of red shiner (Cyprinella lutrensis), a minnow known to displace and hybridize with native species, to reconstruct invasion pathways across the United States (USA). Examination of mitochondrial cytochrome-b variation found that native range populations of red shiner fall into four highly divergent lineages that likely warrant species recognition. Introduced red shiner populations in the eastern and western USA are derived from only two of these lineages. Western USA populations originate from the mid-western and western genetic lineages, whereas eastern introductions derive only from the mid-western lineage. Western USA invasive populations exhibit fewer, but more diverse haplotypes compared to eastern USA invasive populations. We also recovered an undescribed, divergent lineage of Cyprinella that has been cryptically introduced into the western USA, which raises the possibility that hybridization has proceeded following secondary contact between previously allopatric lineages. Approximate Bayesian Computation modeling suggests that the disjunct distribution of red shiner across North America is an agglomeration of independent regional invasions with distinct origins, rather than stepwise advance of an invasion front or secondary introductions across regions. Thus localized control may be effective in managing non-native red shiner, including further spread to areas of conservation concern.

The Interaction between Root Herbivory and Competitive Ability of Native and Invasive-Range Populations of Brassica nigra.

The evolution of increased competitive ability (EICA) hypothesis predicts that escape from intense herbivore damage may enable invasive plants to evolve higher competitive ability in the invasive range. Below-ground root herbivory can have a strong impact on plant performance, and invasive plants often compete with multiple species simultaneously, but experimental approaches in which EICA predictions are tested with root herbivores and in a community setting are rare. Here, we used Brassica nigra plants from eight invasive- and seven native-range populations to test whether the invasive-range plants have evolved increased competitive ability when competing with Achillea millefolium and with a community (both with and without A. millefolium). Further, we tested whether competitive interactions depend on root herbivory on B. nigra by the specialist Delia radicum. Without the community, competition with A. millefolium reduced biomass of invasive- but not of native-range B. nigra. With the community, invasive-range B. nigra suffered less than native-range B. nigra. Although the overall effect of root herbivory was not significant, it reduced the negative effect of the presence of the community. The community produced significantly less biomass when competing with B. nigra, irrespective of the range of origin, and independent of the presence of A. millefolium. Taken together, these results offer no clear support for the EICA hypothesis. While native-range B. nigra plants appear to be better in dealing with a single competitor, the invasive-range plants appear to be better in dealing with a more realistic multi-species community. Possibly, this ability of tolerating multiple competitors simultaneously has contributed to the invasion success of B. nigra in North America.

Invasion of Brassica nigra in North America: distributions and origins of chloroplast DNA haplotypes suggest multiple introductions

Deciphering the origin of invasive plant species, whether or not there have been multiple introductions, and genetic differentiations between invasive and native ranges is crucial in testing hypotheses underlying biological invasions. Here, we applied traditional population genetic analyses to unravel the phylogeographical relationships among invasive (North American) and native (North African, Mediterranean region, and Eurasian) range populations of Brassica nigra using chloroplast DNA. We sequenced chloroplast DNA intron (trnF–trnL) for 284 individuals representing 36 native and 15 invasive range populations of B. nigra. Thirty-two haplotypes were found over the whole data set. A similarity between the invasive range and native range populations in genetic diversity combined with results from analyses of molecular variance and gene genealogies suggest that invasive B. nigra populations were introduced from multiple sources in the native range. More generally, this study adds to the growing body of data on the genetic patterns involved in biological invasions that is crucial to our understanding of the evolutionary trajectories of invasive populations.

Five decades of invasion genetics.

Five decades of invasion genetics.

Invasion of Bromus tectorum (L.) into California and the American Southwest: rapid, multi-directional and genetically diverse

The arrival and subsequent spread of the invasive annual grass Bromus tectorum into California and much of the American Southwest was documented by assembling the grass’s early regional collection history in conjunction with analysis of its genetic variation at 25 allozyme loci within 60 widely separated populations. Herbarium records collected ca. 1900, coupled with the distribution of multilocus genotypes, substantiate the view that the invasion of B. tectorum into our study area was rapid, multi-directional, and genetically diverse. The invasion in California and the American Southwest appears to have followed three distinct pathways: (1) direct introduction from native range populations (e.g., the Pgi-2b multilocus genotype), (2) range expansion as descendants of populations in Eastern North America migrated westward (e.g., Pgm-1a and Pgm-2a), and (3) separate introduction(s) into Northern California and Southern Arizona from the Pacific Northwest (e.g., Got-4c). Populations in California and the American Southwest have, on average, lower genetic diversity (A = 1.03, %P = 3.27 and Hexp = 0.007) compared with populations from other regions in North America. Most of this genetic diversity however is partitioned within populations rather than among populations (GST = 0.277). For an introduced species with a broad invasive range, such as B. tectorum in North America, our results indicate that multiple pathways likely contributed to its current (and potentially expanding) geographic distribution.

Invasive legumes encounter similar soil fungal communities in their non-native and native ranges in Australia

Acacias are globally one of the most successful invaders, but relatively little is known about the role of soil microbial communities, particularly fungi, in their invasion success. We assessed intra- and interspecific variation in the soil fungal communities of five legumes native to either south-east (Acacia longifolia, Acacia melanoxylon – invasive in the south-west) or south-west (Acacia cyclops, Acacia saligna, Paraserianthes lophantha – invasive in the south-east) Australia across their Australian non-native and native ranges. Soil samples were collected from around the roots (up to 5 cm) of each legume species from multiple populations and soil fungal communities were amplified and 454 pyrosequenced. Results revealed a significant interaction between host species and geographic location (i.e., south-east vs south-west) suggesting that among-population differences in fungal communities were largely driven by geographic-scale variation between south-east and south-west Australia. However, pairwise analyses of range effects within species showed that soil fungal communities were not different between non-native and native range populations for any host species except for A. cyclops, suggesting that this species may be more of a generalist than the other legumes studied. Pairwise analyses between species revealed considerable variation in soil fungal communities. Our work suggests that these legume species, introduced into novel ranges across the continent, whether south-east or south-west, generally associate with similar soil fungal communities, indicating that soil fungal communities in non-native ranges are unlikely to have constrained or facilitated the invasion success of these legumes.

Introduced populations as genetic reservoirs for imperiled species: a case study of the Arkansas River Shiner (Notropis girardi)

The Arkansas River Shiner is a threatened species that has been extirpated throughout much of its native range (Arkansas River drainage) and remaining populations are imperiled. Prior to 1978, this species was accidently introduced to the Pecos River (Rio Grande drainage) via bait bucket, and has since persisted for over 30 years. Genetic data show that the Pecos River population maintains comparable levels of diversity at mitochondrial DNA and microsatellite loci relative to native range populations. Hence, we examined several factors that could be responsible for high introduced genetic diversity including (a) multiple introductions from genetically distinct sources (b) introduction of individuals from a genetically diverse source followed by rapid population expansion, (c) presence of life-history traits that foster propagule diversity and wide spatio-temporal demographic and genetic mixing; and (d) introduction to a suitable habitat in the non-native range. Our findings indicate Arkansas River Shiner was likely introduced from the Canadian River and subsequently experienced rapid population expansion that mitigated loss of diversity during the founding event. Threats to native Arkansas River Shiner have increased due to ongoing drought and water resource development, thus a finding of high diversity in the Pecos River suggests conservation significance of this non-native population. Further, it identifies the Pecos River as both a refuge for native endemic fishes and of genetic diversity of introduced, yet threatened, species.

No consistent association between changes in genetic diversity and adaptive responses of Australian acacias in novel ranges

Common garden studies comparing trait differences of exotic species between native and introduced ranges rarely incorporate an analysis of genetic variation, but simply infer that trait shifts between ranges are genetically determined. We compared four growth-related traits (total biomass, relative growth rate RGR, specific leaf area SLA, and root to shoot ratio R:S) of five invasive Fabaceae species (Acacia cyclops, A. longifolia, A. melanoxylon, A. saligna, Paraserianthes lophantha), grown in a common garden experiment using seeds from introduced and native ranges across Australia. Chloroplast microsatellite loci were used to compare genetic diversity of native and introduced populations to determine standing genetic diversity and infer introduction history. We asked whether shifts in traits associated with faster growth due to enemy release in the introduced range were associated with levels of genetic diversity associated with introduction history. We found differences in traits between ranges, although these traits varied among the species. Compared to native-range populations, introduced-range Acacia longifolia had greater biomass and larger SLA; A. cyclops had greater RGR; and A. melanoxylon displayed lower R:S. Genetic diversity in the introduced range was lower for one of those species, A. longifolia, and two others that did not show differences in traits, A. saligna and P. lophantha. Diversity was higher in the introduced range for A. melanoxylon and did not differ among ranges for A. cyclops. These patterns of genetic diversity suggest that a genetic bottleneck may have occurred following the introduction of A. longifolia, A. saligna and P. lophantha. In contrast greater or comparable genetic diversity in the introduced range for A. melanoxylon and A. cyclops suggests introductions from multiple sources. This study has shown that a reduction in genetic diversity in the introduced range is not necessarily associated with a reduced capacity for adaptive responses or invasion potential in the novel range.

InvasiveMicrostegiumpopulations consistently outperform native range populations across diverse environments

Plant species introduced into novel ranges may become invasive due to evolutionary change, phenotypic plasticity, or other biotic or abiotic mechanisms. Evolution of introduced populations could be the result of founder effects, drift, hybridization, or adaptation to local conditions, which could enhance the invasiveness of introduced species. However, understanding whether the success of invading populations is due to genetic differences between native and introduced populations may be obscured by origin x environment interactions. That is, studies conducted under a limited set of environmental conditions may show inconsistent results if native or introduced populations are differentially adapted to specific conditions. We tested for genetic differences between native and introduced populations, and for origin x environment interactions, between native (China) and introduced (U.S.) populations of the invasive annual grass Microstegium vimineum (stiltgrass) across 22 common gardens spanning a wide range of habitats and environmental conditions. On average, introduced populations produced 46% greater biomass and had 7.4% greater survival, and outperformed native range populations in every common garden. However, we found no evidence that introduced Microstegium exhibited greater phenotypic plasticity than native populations. Biomass of Microstegium was positively correlated with light and resident community richness and biomass across the common gardens. However, these relationships were equivalent for native and introduced populations, suggesting that the greater mean performance of introduced populations is not due to unequal responses to specific environmental parameters. Our data on performance of invasive and native populations suggest that post-introduction evolutionary changes may have enhanced the invasive potential of this species. Further, the ability of Microstegium to survive and grow across the wide variety of environmental conditions demonstrates that few habitats are immune to invasion.

Getting here from there: testing the genetic paradigm underpinning introduction histories and invasion success

AbstractAim To explore the potential of genetic processes and mating systems to influence successful plant invasions, we compared genetic diversity of the highly invasive tropical treelet,Miconia calvescens,in nine invasive populations and three native range populations. Specifically, we tested how genetic diversity is partitioned in native and invaded regions, which have different invasion histories (multiple vs. single introductions). Lastly, we infer how levels of inbreeding in different regions impact invasion success.Location Invaded ranges in the Pacific (Hawaii, Tahiti, New Caledonia) and Australia and native range in Costa Rica.Methods Genetic diversity was inferred by analysing variation at nine microsatellite loci in 273 individuals from 13 populations ofM. calvescens. Genetic structure was assessed usingamova, isolation by distance (IBD) within regions, a Bayesian clustering approach, and principal coordinates analysis.Results Microsatellite analysis revealed that invaded regions exhibit low levels of allelic richness and genetic diversity with few private alleles. To the contrary, in the native range, we observed high levels of allelic richness, high heterozygosity and 78% of all private alleles. Surprisingly, despite evident genetic bottlenecks in all invasive regions, similarly high levels of inbreeding were detected in both invasive and native ranges (FIS: 0.345 and 0.399, respectively). Bayesian clustering analysis showed a lack of geographical structure in the Pacific and evidence of differing invasion histories between the Pacific and Australia. While Pacific populations are derived from a single introduction to the region, multiple introductions have taken place in Australia from different source regions.Main conclusions Multiple introductions have not resulted in increased genetic diversity forM. calvescensinvasions. Moreover, similar inbreeding levels between native and invaded ranges suggests that there is no correlation between levels of inbreeding and levels of standing genetic diversity forM. calvescens.Overall, our results show that neither inbreeding nor low genetic diversity is an impediment to invasion success.

Greater performance of introduced vs. native range populations of Microstegium vimineum across different light environments

Non-native plant invaders may undergo evolutionary changes through founder effects, hybridization, adaptation to novel environments, or other processes. Genetic changes in introduced populations may promote invasiveness by increasing plant vigor and plasticity. To determine if introduced populations of the annual grass Microstegium vimineum exhibit greater growth than populations from the native range, we grew plants from 10 native (China) and 10 introduced (U.S.) populations in the greenhouse under two light environments and evaluated growth and morphological traits across two harvest dates. Microstegium from introduced populations had on average 50% and 35% greater biomass in the shade and sun, respectively, than native populations at the first harvest and 59% and 33% greater biomass by the second harvest date. We found no difference in plasticity for growth across the light treatments between native and introduced populations. There were significant morphological differences in resource allocation with native populations producing greater leaf area and leaf mass per stem mass than introduced populations. However, introduced populations produced more biomass overall, despite lower allocation to leaves, which suggests greater efficiency of photosynthesis or lower respiration. These results demonstrate significant genetic differences between introduced and native populations of Microstegium for growth and morphological characteristics. Evolution of Microstegium and other introduced species may complicate the prediction and management of biological invasions.

Suitability of a New Plant Invader as a Target for Biological Control in Florida

AbstractThe suitability of a target weed for classical biological control should be considered early in the process of plant invasion. Concerns have been raised about the recent arrival ofMikania micranthaKunth in south Florida and its potential to spread and invade natural and managed ecosystems. This weed is native to the neotropics, and has been introduced into many Asian countries and, more recently, into Australia. In Asia,M. micranthais particularly problematic in plantation crops, but also threatens natural areas and disturbed ecosystems. Several aspects of the biology and ecology ofM. micranthaare discussed in this review to evaluate its suitability as a target of biological control in Florida. Based on an ecological niche model, the climate in southern and central Florida is highly favorable for the invasion of this weed. Previous biological control programs provide valuable information for Florida scientists about the availability of natural enemies and potential areas for future foreign surveys. Genetic comparison of the Florida population and native range populations, in addition to climate matching, should be considered when selecting areas for foreign exploration. Finally, the authors used a scoring system and risk-benefit–cost analysis to evaluateM. micranthaas a potential target for biological control in Florida. We suggest that similar feasibility evaluations should be conducted not only for well-established problematic weeds but also for new invaders with a known history of invasiveness.

Linking habitat quality with genetic diversity: a lesson from great bustards in Spain

The effects of habitat loss and fragmentation on the genetic structure and variability of wild populations have received wide empirical support and theoretical formalization. By contrast, the effects of habitat quality seem largely underinvestigated, partly due to technical difficulties in properly assessing habitat quality. In this study, we combine geographic information system (GIS)-based habitat-quality modelling with a landscape genetics approach based on mitochondrial DNA markers to evaluate the possible influence of habitat quality on the levels and distribution of genetic diversity in a range of natural populations (n = 15) of Otis tarda throughout Spain. Ninety-three percent of the population represented by our countrywide sample lives in good-quality habitats, while 4.5% and 2.5% occur respectively in intermediate and poor habitats. Habitat quality was highly correlated with patch size, population size and population density, indicating the reliability and predictive power of the habitat suitability model. Genetic diversity was significantly correlated with habitat quality, size and density of the population, but not with patch size. Three of a total of 20 existing matrilineages from the species’ current genetic pool are restricted to poor-quality habitats. This study therefore highlights the importance of considering both population genetics and habitat quality in a species of high conservation priority.

Population admixture, biological invasions and the balance between local adaptation and inbreeding depression

When previously isolated populations meet and mix, the resulting admixed population can benefit from several genetic advantages, including increased genetic variation, the creation of novel genotypes and the masking of deleterious mutations. These admixture benefits are thought to play an important role in biological invasions. In contrast, populations in their native range often remain differentiated and frequently suffer from inbreeding depression owing to isolation. While the advantages of admixture are evident for introduced populations that experienced recent bottlenecks or that face novel selection pressures, it is less obvious why native range populations do not similarly benefit from admixture. Here we argue that a temporary loss of local adaptation in recent invaders fundamentally alters the fitness consequences of admixture. In native populations, selection against dilution of the locally adapted gene pool inhibits unconstrained admixture and reinforces population isolation, with some level of inbreeding depression as an expected consequence. We show that admixture is selected against despite significant inbreeding depression because the benefits of local adaptation are greater than the cost of inbreeding. In contrast, introduced populations that have not yet established a pattern of local adaptation can freely reap the benefits of admixture. There can be strong selection for admixture because it instantly lifts the inbreeding depression that had built up in isolated parental populations. Recent work in Silene suggests that reduced inbreeding depression associated with post-introduction admixture may contribute to enhanced fitness of invasive populations. We hypothesize that in locally adapted populations, the benefits of local adaptation are balanced against an inbreeding cost that could develop in part owing to the isolating effect of local adaptation itself. The inbreeding cost can be revealed in admixing populations during recent invasions.

Vegetative reproduction facilitates early expansion of Phyla canescens in a semi-arid floodplain

Phyla canescens (Verbenaceae, hereafter lippia) is an invasive perennial forb from South America that is now widespread in Australia, threatening the biological values of internationally significant wetlands (Ramsar listed) and the productivity of the grazing industry (Crawford 2008; Earl 2003). Under certain conditions, lippia can displace native herbaceous vegetation and form mono-specific stands, but little is known about the process of colonization and early invasion. Lippia has a dual reproductive strategy, recruiting via seedlings and vegetative fragments in periods following inundation (Macdonald 2008). Determining the relative contribution of vegetative and sexual reproduction for lippia across environmental gradients is important for management action—if spread is primarily by vegetative fragments then control efforts should be focussed on managing vectors (e.g. movement of stock and vehicles), whereas if spread is mostly by seeds then management should focus on reducing the conditions favourable to seed production and seedling establishment. The predominant reproductive mode also has implications for the selection of biocontrol agents. A comparison of lippia in Australia with native range populations found that Australian populations had evolved to invest more energy in sexual reproduction than in the native range (Xu et al. 2009). Genetic analysis found that the importance of vegetative and sexual reproduction is highly variable among populations in Australia (Fatemi and Gross, unpublished data). In some cases, populations exhibited extremely low diversity, with single clones covering distances of up to 100 m and in others, genetic diversity was relatively high with samples 20 m apart representing genetically distinct individuals (Fatemi and Gross, unpublished data). It remains unknown what factors influence the mode of reproduction in different populations in Australia but it is likely that the type of flood event and propagule availability are important. Previous field studies have found that seedling recruitment was the predominant reproductive mode (approx. 70%) following winter flooding, in single site studies (Macdonald 2008; Price et al. 2010a). We examine the density of recruits, dispersal distance and direction from adult plants, and mode of reproduction in a semi-arid floodplain. The study area J. N. Price M. J. Macdonald C. L. Gross I. H. Simpson Ecosystem Management, University of New England, Armidale, NSW 2351, Australia

Are mangroves in the tropical Atlantic ripe for invasion? Exotic mangrove trees in the forests of South Florida

Two species of mangrove trees of Indo-Pacific origin have naturalized in tropical Atlantic mangrove forests in South Florida after they were planted and nurtured in botanic gardens. Two Bruguiera gymnorrhiza trees that were planted in the intertidal zone in 1940 have given rise to a population of at least 86 trees growing interspersed with native mangrove species Rhizophora mangle, Avicennia germinans and Laguncularia racemosa along 100 m of shoreline; the population is expanding at a rate of 5.6% year−1. Molecular genetic analyses confirm very low genetic diversity, as expected from a population founded by two individuals. The maximum number of alleles at any locus was three, and we measured reduced heterozygosity compared to native-range populations. Lumnitzera racemosa was introduced multiple times during the 1960s and 1970s, it has spread rapidly into a forest composed of native R. mangle, A. germinans, Laguncularia racemosa and Conocarpus erectus and now occupies 60,500 m2 of mangrove forest with stem densities of 24,735 ha−1. We estimate the population growth rate of Lumnitzera racemosa to be between 17 and 23% year−1. Populations of both species of naturalized mangroves are dominated by young individuals. Given the long life and water-dispersed nature of propagules of the two exotic species, it is likely that they have spread beyond our survey area. We argue that the species-depauperate nature of tropical Atlantic mangrove forests and close taxonomic relatives in the more species-rich Indo-Pacific region result in the susceptibility of tropical Atlantic mangrove forests to invasion by Indo-Pacific mangrove species.

Revealing the geographic origin of an invasive lizard: the problem of native population genetic diversity

The brown anole, Anolis sagrei, is one of the most widespread and successful colonisers of the diverse Anolis genus, which comprises c. 400 species occurring naturally in Central and South America and the Caribbean. Based on extensive between and within population sampling from a previously published study (334 mitochondrial DNA sequences) and sampling for this study (37 mtDNA sequences), we reconstruct a phylogeny and produce a haplotype network to assign a recently introduced population in St Vincent, Lesser Antilles to its geographic origin. A single haplotype was present in the St Vincent population, which was identical to a haplotype from Tampa, FL. We show that genetic diversity within native range populations, combined with low frequencies of introduced haplotypes in native ranges, may impair attempts to identify source populations, even despite intensive sampling effort. The absence of mtDNA haplotype diversity suggests a significant genetic founder effect within the St Vincent population.

Population Genetics of Aedes albopictus (Diptera: Culicidae) Invading Populations, Using Mitochondrial nicotinamide Adenine Dinucleotide Dehydrogenase Subunit 5 Sequences.

Aedes albopictus (Skuse) (Diptera: Culicidae), the Asian tiger mosquito indigenous to Asia, now an invasive species worldwide, is an important vector for several arboviruses. Genetic analysis using the mitochondrial nicotinamide adenine dinucleotide dehydrogenase subunit 5 (ND5) gene was carried out in populations from Cameroon (n = 50), Hawaii (n = 38), Italy (n = 20), the continental United States, Brazil, and its native range. Data for Brazil, the continental United States, and the native range was obtained from Birungi and Munstermann (2002). Direct sequencing was used to identity unique haplotypes. The limited phylogeographic partitioning of haplotypes with low levels of sequence divergence in both Cameroon and Hawaii was consistent with the population structure of Ae. albopictus in the United States and Brazil. Four new haplotypes were identified from the samples from Cameroon and Hawaii, adding to previously described haplotypes. Hawaii shared a haplotype with Cameroon that was unique to these two regions. Hawaii also had higher overall haplotype diversity than seen in previous continental United States, Brazil, or native range populations. Hawaiian, Cameroon, and Italian populations did not share haplotypes with Brazil, which validates the earlier mitochondrial DNA studies indicating a separate introduction of this species into Brazil.