Subterranean archipelago in the Australian arid zone: mitochondrial DNA phylogeography of amphipods from central Western Australia

In 1998, a unique subterranean ecosystem was discovered in numerous isolated calcrete (carbonate) aquifers in the arid Yilgarn region of Western Australia. Previous morphological and genetic analyses of a subterranean water beetle fauna suggest that calcrete aquifers are equivalent to closed island habitats that have been isolated for millions of years. We tested this hypothesis further by phylogeographic analyses of subterranean amphipods (Crangonyctoidea: Paramelitidae and Hyalidae) using mitochondrial DNA sequence data derived from the cytochrome oxidase I gene. Phylogenetic analyses and population genetic analyses (samova) provided strong evidence for the existence of at least 16 crangonyctoid and six hyalid divergent mitochondrial lineages, each restricted in their distribution to a single calcrete aquifer, in support of the 'subterranean island (archipelago) hypothesis' and extending its scope to include entirely water respiring invertebrates. Sequence divergence estimates between proximate calcrete populations suggest that calcretes have been isolated at least since the Pliocene, coinciding with a major aridity phase that led to the intermittent drying of surface water. The distribution of calcretes along palaeodrainage channels and on either side of drainage divides, have had less influence on the overall phylogeographic structure of populations, with evidence that ancestral crangonyctoid and hyalid species moved between catchments multiple times prior to their isolation within calcretes. At least two potential modes of evolution may account for the diversity of subterranean amphipod populations: dispersal/vicariance of stygobitic species or colonization of calcretes by surface species and independent evolution of stygobitic characteristics.     

Molecular Markers Reveal Limited Population Genetic Structure in a North American Corvid,Clark’s Nutcracker (Nucifraga columbiana)

The genetic impact of barriers and Pleistocene glaciations on high latitude resident species has not been widely investigated. The Clark’s nutcracker is an endemic North American corvid closely associated with Pinus-dominated forests. The nutcracker’s encompasses known barriers to dispersal for other species, and glaciated and unglaciated areas. Clark’s nutcrackers also irruptively disperse long distances in search of pine seed crops, creating the potential for gene flow among populations. Using the highly variable mitochondrial DNA control region, seven microsatellite loci, and species distribution modeling, we examined the effects of glaciations and dispersal barriers on population genetic patterns and population structure of nutcrackers. We sequenced 900 bp of mitochondrial control region for 169 individuals from 15 populations and analysed seven polymorphic microsatellite loci for 13 populations across the Clark’s nutcracker range. We used species distribution modeling and a range of phylogeographic analyses to examine evolutionary history. Clark’s nutcracker populations are not highly differentiated throughout their range, suggesting high levels of gene flow among populations, though we did find some evidence of isolation by distance and peripheral isolation. Our analyses suggested expansion from a single refugium after the last glacial maximum, but patterns of genetic diversity and paleodistribution modeling of suitable habitat were inconclusive as to the location of this refugium. Potential barriers to dispersal (e.g. mountain ranges) do not appear to restrict gene flow in Clark’s nutcracker, and postglacial expansion likely occurred quickly from a single refugium located south of the ice sheets.     

Dispersal of the Ponto-Caspian amphipod Echinogammarus ischnus: invasion waves from the Pleistocene to the present

The geographical range of the amphipod crustacean Echinogammarus ischnus has expanded over the past century from the Ponto-Caspian region to Western Europe, the Baltic Sea, and the Great Lakes of North America. The present study explores the phylogeographic patterns of this amphipod across its current distribution, based on an examination of nucleotide diversity in the mitochondrial cytochrome c oxidase subunit I (COI) gene. Marked genetic divergence exists among populations of E. ischnus from the Black and Caspian Seas, as well as those from the drainage system of the Black Sea. This divergence suggests the prolonged geographic isolation of these native populations, reflecting the limited dispersal capability of E. ischnus. By contrast, invading populations are characterized by a lack of genetic variation; a single mitochondrial genotype of Black Sea origin has colonized sites from the Rhine River to North America. The dispersal pattern in E. ischnus is very similar to that in the Ponto-Caspian cladoceran Cercopagis pengoi. Despite their contrasting life history strategies, these invading species followed the same route of invasion from the northern Black Sea to the Baltic Sea region, and subsequently to North America.     

Deep phylogeographic structuring of populations of the trapdoor spider Moggridgea tingle (Migidae) from southwestern Australia: evidence for long-term refugia within refugia

Southwestern Australia has been recognized as a biodiversity hot spot of global significance, and it is particularly well known for its considerable diversity of flowering plant species. Questions of interest are how this region became so diverse and whether its fauna show similar diverse patterns of speciation. Here, we carried out a phylogeographic study of trapdoor spiders (Migidae: Moggridgea), a presumed Gondwanan lineage found in wet forest localities across southwestern Australia. Phylogenetic, molecular clock and population genetic analyses of mitochondrial (mtDNA) COI gene and ITS rRNA (internal transcribed spacer) data revealed considerable phylogeographic structuring of Moggridgea populations, with evidence for long-term (>3 million years) isolation of at least nine populations in different geographic locations, including upland regions of the Stirling and Porongurup Ranges. High levels of mtDNA divergence and no evidence of recent mitochondrial gene flow among valley populations of the Stirling Range suggest that individual valleys have acted as refugia for the spiders throughout the Pleistocene. Our findings support the hypothesis that climate change, particularly the aridification of Australia after the late Miocene, and the topography of the landscape, which allowed persistence of moist habitats, have been major drivers of speciation in southwestern Australia.     

Evidence for population fragmentation within a subterranean aquatic habitat in the Western Australian desert

The evolution of subterranean animals following multiple colonisation events from the surface has been well documented, but few studies have investigated the potential for species diversification within cavernicolous habitats. Isolated calcrete (carbonate) aquifers in central Western Australia have been shown to contain diverse assemblages of aquatic subterranean invertebrate species (stygofauna) and to offer a unique model system for exploring the mechanisms of speciation in subterranean ecosystems. In this paper, we investigated the hypothesis that microallopatric speciation processes (fragmentation and isolation by distance (IBD)) occur within calcretes using a comparative phylogeographic study of three stygobiontic diving beetle species, one amphipod species and a lineage of isopods. Specimens were sequenced for the mitochondrial cytochrome c oxidase 1 gene from three main sites: Quandong Well, Shady Well (SW) and Mt. Windarra (MW), spanning a 15 km region of the Laverton Downs Calcrete. Phylogenetic and haplotype network analyses revealed that each species possessed a single divergent clade of haplotypes that were present only at the southern MW site, despite the existence of other haplotypes at MW that were shared with SW. IBD between MW and SW was evident, but the common phylogeographic pattern most likely resulted from fragmentation, possibly by a salt lake adjacent to MW. These findings suggest that microallopatric speciation within calcretes may be a significant diversifying force, although the proportion of stygofauna species that may have resulted from in situ speciation in this system remains to be determined.     

Phylogeographic insights into an irruptive pest outbreak

Irruptive forest insect pests cause considerable ecological and economic damage, and their outbreaks have been increasing in frequency and severity. We use a phylogeographic approach to understand the location and progression of an outbreak by the MPB (Dendroctonus ponderosae Hopkins), an irruptive bark beetle that has caused unprecedented damage to lodgepole pine forests in western North America and is poised to expand its range across the boreal forest. We sampled MPB populations across British Columbia and Alberta and used phylogeographic methods to describe lineage diversification, characterize population structure, investigate expansion dynamics, and identify source populations of the outbreak. Using 1181 bp of mitochondrial DNA sequence from 267 individuals, we found high haplotype diversity, low nucleotide diversity, and limited lineage diversification. The overall pattern was consistent with isolation by distance at a continental scale, and with reduced diversity and population structure in the northerly, outbreak regions. Post-Pleistocene expansion was detected, however more recent expansion signals were not detected, potentially due to the size and rapid rate of range expansion. Based on the limited genetic structure, there were likely multiple source populations in southern British Columbia, although the magnitude of the demographic expansion and rate of spread have obscured the signature of these source populations. Our data highlight the need for caution in interpreting phylogeographic results for species with similar demographics.     

Genetic consequences of Pleistocene glaciations for the tundra vole (Microtus oeconomus) in Beringia

Repeated glacial events during the Pleistocene fragmented and displaced populations throughout the northern continents. Different models of the effects of these climate-driven events predict distinct phylogeographic and population genetic outcomes for high-latitude faunas. The role of glaciations in (i) promoting intraspecific genetic differentiation and (ii) influencing genetic diversity was tested within a phylogeographic framework using the rodent Microtus oeconomus. The spatial focus for the study was Beringia, which spans eastern Siberia and northwestern North America, and was a continental crossroads and potential high arctic refugium during glaciations. Variation in mitochondrial DNA (cytochrome b and control region; 214 individuals) and nuclear DNA (ALDH1 intron; 63 individuals) was investigated across the Beringian region. Close genetic relationships among populations on either side of the Bering Strait are consistent with a history of periodic land connections between North America and Asia. A genetic discontinuity observed in western Beringia between members of a Central Asian clade and a Beringian clade is geographically congruent with glacial advances and with phylogeographic discontinuities identified in other organisms. Divergent island populations in southern Alaska were probably initially isolated by glacial vicariance, but subsequent differentiation has resulted from insularity. Tests of the genetic effects of postglacial colonization were largely consistent with expansion accompanied by founder effect bottlenecking, which yields reduced diversity in populations from recently deglaciated areas. Evidence that populations in the Beringian clade share a history of expansion from a low-diversity ancestral population suggests that Beringia was colonized by a small founder population from central Asia, which subsequently expanded in isolation.     

Response of a southern temperate marsupial, the Tasmanian pademelon (Thylogale billardierii), to historical and contemporary forest fragmentation

Despite only limited Pleistocene glacial activity in the southern hemisphere, temperate forest species experienced complex distributional changes resulting from the combined effects of glaciation, sea level change and increased aridity. The effects of these historical processes on population genetic structure are now overlain by the effects of contemporary habitat modification. In this study, 10 microsatellites and 629 bp of the mitochondrial control region were used to assess the effects of historical forest fragmentation and recent anthropogenic habitat change on the broad-scale population genetic structuring of a southern temperate marsupial, the Tasmanian pademelon. A total of 200 individuals were sampled from seven sites across Tasmania and two islands in Bass Strait. High mitochondrial and nuclear genetic diversity indicated the maintenance of large historical population sizes. There was weak phylogeographical structuring of haplotypes, although all King Island haplotypes and three Tasmanian haplotypes formed a divergent clade implying the mid-Pleistocene isolation of a far northwestern population. Both the mitochondrial and nuclear data indicated a division of Tasmanian populations into eastern and western regions. This was consistent with a historical barrier resulting from increased aridity in the lowland 'midlands' region during glacial periods, and with a contemporary barrier resulting from recent habitat modification in that region. In Tasmania, gene flow appears to have been relatively unrestricted during glacial maxima in the west, while in the east there was evidence for historical expansion from at least one large glacial refuge and recolonization of Flinders Island.     

Testing hypotheses of population structuring in the Northeast Atlantic Ocean and Mediterranean Sea using the common cuttlefish Sepia officinalis

Population structuring in species inhabiting marine environments such as the Northeast Atlantic Ocean (NEA) and Mediterranean Sea (MS) has usually been explained based on past and present physical barriers to gene flow and isolation by distance (IBD). Here, we examined the relative importance of these factors on population structuring of the common cuttlefish Sepia officinalis by using methods of phylogenetic inference and hypothesis testing coupled with coalescent and classical population genetic parameter estimation. Individuals from 10 Atlantic and 15 Mediterranean sites were sequenced for 659 bp of the mitochondrial COI gene (259 sequences). IBD seems to be the main factor driving present and past genetic structuring of Sepia populations across the NEA-MS, both at large and small geographical scales. Such an evolutionary process agrees well with some of the biological features characterizing this cuttlefish species (short migrations, nektobenthic habit, benthic eggs hatching directly to benthic juveniles). Despite the many barriers to migration/gene flow suggested in the NEA-MS region, genetic population fragmentation due to past isolation of water masses (Pleistocene; 0.56 million years ago) and/or present-day oceanographic currents was only detected between the Aegean-Ionian and western Mediterranean Seas. Restricted gene flow associated with the Almería-Oran hydrographic front was also suggested between southern and eastern Spanish populations. Distinct population boundaries could not be clearly determined, except for the Aegean-Ionian stock. Two Atlantic and five Mediterranean samples showed evidence of current decline in genetic diversity, which may indicate over-exploitation of Sepia in both marine regions.     

Comparison of phylogeographic structure and population history of two Phrynocephalus species in the Tarim Basin and adjacent areas

An aridification of the Tarim Basin and adjacent areas since middle Pleistocene has produced significant genetic structuring of the local fauna. We examined the phylogeographic patterns, population structure and history of Phrynocephalus axillaris and Phrynocephalus forsythii using a mitochondrial fragment ND4-tRNA(LEU). Phylogenetic hypotheses were constructed using maximum parsimony and Bayesian inference, and the divergence times of major lineages were estimated by BEAST. Population structure and history were inferred by nested clade analysis, neutrality tests, mismatch distribution, and isolation by distance analysis. The two species might have experienced different evolutionary history throughout their current distribution. For P. forsythii, a vicariant event, as a consequence of geological isolation and desert expansion, might have produced the significant divergence between the Tarim and the Yanqi populations. For P. axillaris, populations of the Yanqi, Turpan and Hami Basins might have been established through dispersal during demographic expansion. Climatic fluctuations caused alternate expansion and shrinkage of rivers and oases several times, which likely led to habitat fragmentation for both species. Interaction between vicariance, dispersal and habitat fragmentation produced the current distribution and genetic diversity. The observed difference between the two species may be due partially to their different reproductive modes (ovoviviparous vs. oviparous).     

Phylogeography and environmental diversification of a highly adaptable marine amphipod, Gammarus duebeni

Genetic diversity and phylogeographic population structure in the gammarid amphipod, Gammarus duebeni, were investigated across its broad latitudinal distribution in the NE and NW Atlantic by analysis of mitochondrial DNA sequence. Gammarus duebeni has exceptional tolerance of salinity change and inhabits environments ranging from marine to freshwater. The longstanding debate on whether there are distinct marine and freshwater subspecies was assessed by sampling populations from sites characterized by different salinities. Our sequence data demonstrates that there are two major lineages, with little internal geographic structuring. Evidence is provided to suggest a pre-glacial divergence of these two clades, involving segregation between a region historically associated with the freshwater form and the majority of the marine localities on both sides of the Atlantic. A modern contact zone between the marine and freshwater forms is proposed in western Britain.     

Gene flow connects coastal populations of a habitat specialist,the Clapper Rail Rallus crepitans

Examining population genetic structure can reveal patterns of reproductive isolation or population mixing and inform conservation management. Some avian species are predicted to exhibit minimal genetic differentiation among populations as a result of the species high mobility, with habitat specialists tending to show greater fine‐scale genetic structure. To explore the relationship between habitat specialization and gene flow, we investigated the genetic structure of a saltmarsh specialist with high potential mobility across a wide geographical range of fragmented habitat. Little variation among mitochondrial sequences (620 bp from ND2) was observed among 149 individual Clapper Rails Rallus crepitans sampled along the Atlantic coast of the USA, with the majority of individuals at all sampling sites sharing a single haplotype. Genotyping of nine microsatellite loci across 136 individuals revealed moderate genetic diversity, no evidence of bottlenecks and a weak pattern of genetic differentiation that increased with geographical distance. Multivariate analyses, Bayesian clustering and an AMOVA all suggested a lack of genetic structuring across the Atlantic coast of the USA, with all individuals grouped into a single interbreeding population. Spatial autocorrelation analyses showed evidence of weak female philopatry and a lack of male philopatry. We conclude that high gene flow connecting populations of this habitat specialist may result from the interaction of ecological and behavioural factors that promote dispersal and limit natal philopatry and breeding‐site fidelity. As climate change threatens saltmarshes, the genetic diversity and population connectivity of Clapper Rails may promote resilience of their populations. This finding helps inform about potential fates of other similarly behaving saltmarsh specialists on the Atlantic coast.     

Phylogeography and ecological niche modeling unravel the evolutionary history of the African green toad,Bufotes boulengeri boulengeri (Amphibia: Bufonidae), through the Quaternary

Recent integration of ecological niche models in phylogeographic studies is improving our understanding of the processes structuring genetic variation across landscapes. Previous studies on the amphibian Bufotes boulengeri boulengeri uncovered a surprisingly weak intraspecific differentiation across the Maghreb region. We widely sampled this species from Morocco to Egypt and sequenced one nuclear and three mitochondrial (mtDNA) genes to determine the level of genetic variability across its geographic range. We evaluated these data with ecological niche modeling to reveal its evolutionary history in response to climate change during the Quaternary. Our results highlight some mtDNA phylogeographic structure within this species, with one haplogroup endemic to coastal Morocco, and one haplogroup widely distributed throughout North Africa. No or little genetic differentiation is observed between isolated populations from the Hoggar Mountains, the Sabha district and the islands of Kerkennah and Lampedusa, compared to others populations. This can be explained by the expansion of the distribution range of B. b. boulengeri during glacial periods. This might have facilitated the species’ dispersal and subsequent gene flow between most North African localities.     

Genetic homogeneity of the Sedgling Nehalennia speciosa (Odonata: Coenagrionidae) indicates a single Würm glacial refugium and trans‐Palaearctic postglacial expansion

The phylogeographic structures of taiga species often support the hypothesis of East Palaearctic refugia for these taxa, but the phylogeographic structures of northern temperate and southern boreal bog species are still poorly understood. Therefore, we analysed the genetic diversity and differentiation of a stenotopic damselfly, Nehalennia speciosa, across its trans‐Palaearctic range by means of sequencing two mitochondrial gene fragments, 16S rRNA‐ND1 and cytochrome c oxidase II. Only four single nucleotide polymorphisms were detected over the 1130 sequenced nucleotides. This low genetic diversity and differentiation and thus the lack of phylogeographic structure imply postglacial expansion from a single Würm Ice Age refugium, most likely located in the Far East of Asia, i.e. Manchurian refugium. From here, the species could have colonized large parts of the Palaearctics, including Europe, during the postglacial.     

Contemporary habitat loss reduces genetic diversity in an ecologically specialized butterfly

Aim This study investigated the influence of contemporary habitat loss on the genetic diversity and structure of animal species using a common, but ecologically specialized, butterfly, Theclinesthes albocincta (Lepidoptera: Lycaenidae), as a model. Location South Australia. Methods We used amplified fragment length polymorphism (AFLP) and allozyme datasets to investigate the genetic structure and genetic diversity among populations of T. albocincta in a fragmented landscape and compared this diversity and structure with that of populations in two nearby landscapes that have more continuous distributions of butterflies and their habitat. Butterflies were sampled from 15 sites and genotyped, first using 363 informative AFLP bands and then using 17 polymorphic allozyme loci (n = 248 and 254, respectively). We complemented these analyses with phylogeographic information based on mitochondrial DNA (mtDNA) haplotype information derived from a previous study in the same landscapes. Results Both datasets indicated a relatively high level of genetic structuring across the sampling range (AFLP, F_ST = 0.34; allozyme, F_ST = 0.13): structure was greatest among populations in the fragmented landscape (AFLP, F_ST = 0.15; allozyme, F_ST = 0.13). Populations in the fragmented landscape also had significantly lower genetic diversity than populations in the other two landscapes: there were no detectable differences in genetic diversity between the two continuous landscapes. There was also evidence (r² = 0.33) of an isolation by distance effect across the sampled range of the species. Main conclusions The multiple lines of evidence, presented within a phylogeographic context, support the hypothesis that contemporary habitat fragmentation has been a major driver of genetic erosion and differentiation in this species. Theclinesthes albocincta populations in the fragmented landscape are thus likely to be at greater risk of extinction because of reduced genetic diversity, their isolation from conspecific subpopulations in other landscapes, and other extrinsic forces acting on their small population sizes. Our study provides compelling evidence that habitat loss and fragmentation have significant rapid impacts on the genetic diversity and structure of butterfly populations, especially specialist species with particular habitat preferences and poor dispersal abilities.     

DNA barcoding of stygofauna uncovers cryptic amphipod diversity in a calcrete aquifer in Western Australia's arid zone

The arid Yilgarn region of Western Australia contains numerous subterranean calcrete aquifers with unique assemblages of obligate groundwater invertebrates (stygofauna). We aimed to establish a DNA barcoding framework for the macro-invertebrates present in a single calcrete, as a basis for future assessment of biodiversity of the Yilgarn calcretes and for investigating food webs. Intense sampling of a bore field grid in the Sturt Meadows calcrete was undertaken to obtain representatives of the entire macro-invertebrate ecosystem. A 623-bp fragment of the mitochondrial cytochrome c oxidase 1 (COI) gene was used to provide DNA barcodes for stygobiont macro-invertebrates plus terrestrial organisms that are found in the calcrete. Phylogenetic analyses revealed the existence of 12 divergent monophyletic groups of haplotypes. Subterranean amphipods (Chiltoniidae) showed three groups of COI haplotypes with sequence divergences between them of >11%. Allozyme analyses found a large number of fixed allelic differences between these three amphipod groups, indicating that there are three morphologically cryptic species within the Sturt Meadows calcrete. Unlike the sister triplet of dytiscid beetles present, the amphipods are not sister clades and are more closely related to other Yilgarn and non-Yilgarn amphipods than to each other. Our results show that the aquifer contains at least 12 macro-invertebrate species and DNA barcoding provides a useful means for discriminating species in this system.     

The hypervariable domain of the mitochondrial control region in Atlantic spiny lobsters and its potential as a marker for investigating phylogeographic structuring

Atlantic spiny lobsters support major fisheries in northeastern Brazilian waters and in the Caribbean Sea. To avoid reduction in diversity and elimination of distinct stocks, understanding their population dynamics, including structuring of populations and genetic diversity, is critical. We here explore the potential of using the hypervariable domain in the control region of the mitochondrial DNA as a genetic marker to characterize population subdivision in spiny lobsters, using Panulirus argus as the species model. The primers designed on the neighboring conserved genes have amplified the entire control region (approx. 780 bases) of P. argus and other closely related species. Average nucleotide and haplotype diversity within P. argus were found to be high, and population structuring was hypothesized. The data suggest a division of P. argus into genetically different phylogeographic groups. The hypervariable domain seems to be useful for determining genetic differentiation of geographically distinct stocks of P. argus and other Atlantic spiny lobsters.     

Environmental calcium and mitochondrial DNA polymorphism among local populations of Gammarus fossarum (Crustacea, Amphipoda)

Mitochondrial DNA sequence analysis was used to investigate genetic diversity and phylogeographic population structure among geographically isolated alpine populations of the amphipod Gammarus fossarum. This study was performed across a region with an important glacial history and substantial geographical variations in calcium levels, in order to evaluate the relative impact on the genetic diversity of the population history and this environmental factor known to be associated with local adaptation and population growth. Analysis of the nucleotide sequences for a 376-bp segment of the cytochrome c oxidase I gene in 84 specimens from seven different populations revealed 20 different haplotypes distributed into five major lineages that are not geographically structured. Analysis of molecular variance indicates that the populations from the crystalline massif are less diverse than those living on limestone, suggesting a global correlation between genetic diversity and calcium concentration of the water. However, the role of this environmental factor appears to be indirect, with smaller population size leading to lower genetic diversity.     

Phylogeographic structure of Pinus strobiformis Engelm. across the Chihuahuan Desert filter-barrier

Aim  To explore the genetic and phylogeographic structure of a temperate forest species, Pinus strobiformis Englem., in a subtropical region in the context of climate change during the Pleistocene. It is expected that the colder conditions during glacial stages favoured range expansions of P. strobiformis , thus promoting gene flow.
Location  Mexico and the United States.
Methods  Estimates of genetic diversity and structure were obtained using chloroplast microsatellite loci of 23 populations of P. strobiformis across its entire range, seven neighbouring populations of Pinus ayacahuite Ehrenb. ex. Schtdl, and one population of Pinus flexilis James.
Results  The genetic diversity of P. strobiformis ( H _e = 0.856) was found to be high, especially in western populations, whereas eastern populations were less variable and more genetically similar to P. ayacahuite of central Mexico. We found evidence of significant phylogeographic structure ( N _ST = 0.444; P  =   0.026), high genetic structure ( R _ST = 0.270), and isolation by distance. Pairwise R _ST and samova (spatial analysis of molecular variance) results indicated an east–west partition of genetic variation, with populations within each group showing little differentiation and no isolation by distance.
Main conclusions  The phylogeographic structure of P. strobiformis across the entire range was pronounced, with two main genetic and geographic groups separated by the Chihuahuan Desert. However, within each of the two groups there was little population differentiation and no isolation by distance, suggesting genetic connectivity as a result of population expansions within these areas during glacial stages.     

Population genetic structure of banana corm weevil Cosmopolites sordidus (Germar) in India

The population genetic structure of Cosmopolites sordidus (Germar), an economically important pest of bananas, was studied using the sequence data of the internal transcribed rDNA (ITS1+ITS2) and the mitochondrial ‘COI-tRNA^Leu-COII’ region from seventy nine individuals collected from six sampling locations in India. The ITS data revealed 70% within population variation and non-significant genetic differentiation estimates suggesting lack of phylogeographic sub-structuring. 49% within population variation and highly significant genetic differentiation values were obtained with the mitochondrial data. The Mantel test revealed lack of correlation between genetic and geographic distance with both the markers. Demographic expansion of the populations was confirmed by the star shaped haplotype networks, demographic tests and mismatch distribution curves using both the markers. Molecular diversity indices show a high haplotype diversity (Hd) but low nucleotide diversity (π) suggesting that the populations are closely related. Considering the low self-dispersal ability of the weevils, these results suggest that the range expansion of this banana pest in India has taken place mainly through transport of infested corms and plant material resulting in the weevils forming localised populations which are not genetically distinct from each other. The high gene diversity (Hd) has enabled the weevils to adapt to varying environmental conditions which could explain the range expansion of this pest in India. The observed discrepancy in the genetic differentiation estimates using these two markers can be attributed to the evolutionary dynamics of the nuclear and mitochondrial genomes.