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At least 163 records · Page 9Linked to original sources
PubMed2003

Estimate of the total number of CD8+ clonal expansions in healthy adults using a new DNA heteroduplex-tracking assay for CDR3 repertoire analysis.

A T-cell receptor heteroduplex-tracking assay (TCR-HTA) was developed to analyze the sequence diversity of the TCR beta-chain mRNA of each of the 24 T-cell receptor beta-chain variable region (TRBV). TCR-HTA allowed an estimation of the number of expanded CD8 T-cell clones whose distinct CDR3 domain mRNA made up 2% or more of the transcript of each TRBV subfamily. An average of 40 CD8+ clonal expansions (range 34-49) was detected in three healthy adults. Correct sampling of the complex mRNA transcript populations was documented by the reproducible generation of TCR-HTA patterns using independently generated PCR amplicons. The CDR3 sequence of expanded T-cell clones could be rapidly determined by direct sequencing of DNA heteroduplex bands. CD4+ and CD8+ clonal expansions were found predominantly although not exclusively in CD45RO+ CD62L- effector/memory cells and the majority of expanded T-cell clones were stable over a period of at least 6 months. Fewer CD4+ than CD8+ clonal expansions were detected in peripheral blood cells. By providing a high-resolution method for the detection of clonally expanded T-cell clones and by simplifying the pattern generated using traditional DNA heteroduplex analysis, TCR-HTA is shown to be a sensitive method for assessing levels of oligoclonality and changes in TRBV repertoires.

Adult↗
PubMed2005

The biology and behavior of the longhorned beetle, Dectes texanus on sunflower and soybean.

The biology and behavior of the longhorned beetle Dectes texanus LeConte (Coleoptera: Cerambycidae) was studied on two host plants that suffer economic losses from this pest; sunflower, Helianthus annuus, and soybean, Glycines max. Reciprocal crosses of D. texanus collected from the two plants all produced viable progeny, indicating that conspecific insects attack both crops. Pupae from soybean stalks weighed about 40% less than those from sunflower, and adults fed on soybean lived a mean of 23 days, compared to a mean of 53 days (males) and 76 days (females) for those fed sunflower. A female's larval host plant had no effect on her tendency to ovipuncture plants of either type in a greenhouse trial. A field-tested population collected exclusively from sunflower contained three types of females in similar proportions: those that laid eggs only on sunflower, those that laid only on soybean, and those that laid equally on both host plants. Females in field trials fed more on the plant they had fed on in the laboratory, but soybean-fed females fed more on soybean than did sunflower-fed females. Females fed soybean also made more ovipunctures on soybean plants in field trials than sunflower-fed females, but their responses to sunflower plants were similar. Females displayed higher total ovipositional activity when they encountered sunflower first in the field, and lower total activity when they encountered soybean first. Feeding scores were significantly correlated with ovipunctures and eggs on both plant types. We conclude that sunflower is the preferred host plant, although females will accept soybean when it is the only available food. The results suggest that D. texanus is still in the initial stages of a host range expansion with female host selection behavior demonstrating both genetic influences and phenotypic flexibility. Sunflower represents a nutritionally superior, ancestral host plant and relatively high fitness costs are still associated with utilization of the novel host plant, soybean, costs that may be offset by benefits such as reduced intraspecific competition. These potential benefits and their consequent implications for D. texanus host range evolution are hypothesized and discussed.

Animals↗
PubMed2005

Interaction between founder effect and selection during biological invasion in an aquatic plant.

Long-distance colonization and rapid range expansion associated with biological invasion may have major evolutionary consequences via both stochastic processes and selection. Using large-scale population genetic surveys, we demonstrate a major shift in the relative frequency of sexually fertile diploid versus sexually sterile triploid populations associated with the invasion of North America by a clonal aquatic plant, Butomus umbellatus. Most populations across the native European range were triploid (84% of 108), whereas most introduced populations were diploid (71% of 136). We evaluated the roles of stochastic processes versus natural selection in causing this shift by surveying predominantly neutral genetic variation at 28 RAPD loci. In Europe (EU) we detected 47 distinct genotypes among 142 plants sampled from 71 populations, whereas in North America (NA) we detected only six genotypes among 138 plants from 69 populations. Of the six NA genotypes, a set of four closely related genotypes were found only in triploid populations and a pair of closely related genotypes were found only in diploid populations, and these were genetically divergent from the triploid genotypes. This result is consistent with severe founder effect. Because sex creates genotypic variation and produces offspring with greater dispersal potential than those produced clonally, we tested the hypothesis that sexual reproduction characteristic of diploids has given them a colonization advantage that accounts for their high frequency in NA. However, we found little or no evidence of sexual recruitment in introduced diploids. One very widespread heterozygous genotype occurred in 95% of 38 introduced diploid populations (i.e., 72 of 76 plants surveyed) suggesting predominant clonal reproduction. Moreover genotypic diversity was not higher within or among diploid than triploid populations in either the native or introduced range. Low genetic diversity in diploid populations was also supported by a comparison of within-population quantitative variation for plant size under a common greenhouse environment. Thus, diploids have not been favored during colonization owing to their sexual fertility. However, concurrent studies have shown that NA diploids exhibit a much higher capacity for clonal reproduction, via small vegetative bulbils, than NA triploids, which almost never produce bulbils. The same difference in clonal capacity is not a consistent feature of the native EU populations. Taken together, these results suggest that strong founder effect has set the stage for a major increase in diploid frequency due to the particular, and possibly idiosyncratic, features of the diploid and triploid lineages introduced to North America.

Alismatales↗
PubMed2002

Locating the sources of an invasive pest, grape phylloxera, using a mitochondrial DNA gene genealogy.

Range expansions through human introductions have increased with global commerce and have led to the extinction of native species, alterations in community structure and pest status of the invasive species. Inferring the evolutionary history of invasive species can help to build a firmer footing for management tactics. This study used mitochondrial DNA (mtDNA) sequence comparisons of samples collected from the native and introduced ranges of a pest herbivore of cultivated grapes, grape phylloxera (Daktulosphaira vitifoliae Fitch, Phylloxeridae) to infer the sources and pattern of introductions into worldwide viticulture. Introductions into viticulture from its native North American range first occurred in the mid-19th century. The pattern of spread has suggested a focus of introduction into France, but independent introductions may have occurred elsewhere. The results show that the introduced population represents a limited subsample of the native genetic diversity. The data suggest that most grape phylloxera in viticulture, including all European, have originated in the northeastern USA where the grape species Vitis riparia dominates. There was evidence for independent introductions into South Africa and California. Most California haplotypes were most closely related to native grape phylloxera from the Atlantic Coast on V. vulpina. It is likely that subsequent spread from California into Australia, New Zealand and Peru has occurred.

Animals↗
PubMedDate not supplied

Effects of cavity form and setting expansion of refractory dies on adaptability of Class II (MO and MOD) fired ceramic inlays.

This study investigated the effects of cavity divergence and setting expansion of refractory die material on the adaptability of Class II (MO and MOD) fired ceramic inlays. Standardized Class II (MO and MOD) cavities with two kinds of lateral wall divergence (10 and 20 degrees) were prepared in epoxy resin blocks. A refractory die was prepared from an impression of the epoxy resin cavity in which the setting expansion ranged from 0.04 to 1.14%. A ceramic inlay was fired on each die. The fabricated inlay was inserted into the epoxy resin cavity, and the interfacial distance between the ceramic inlay and the cavity wall at the margin was measured using a reflecting microscope at x100 magnification. The internal fit was measured after sectioning the specimen longitudinally. The results indicate that the setting expansion of the refractory die materials and the divergence of the lateral walls had significant effects on the adaptability of Class II (MO and MOD) fired ceramic inlays. The inlays fabricated on the refractory dies with small setting expansion showed small internal gaps in Class II (MO) cavities. Significantly good adaptation was achieved when the setting expansion was 0.32% or less (p < 0.05). The inlays fabricated on the refractory dies with large setting expansion showed small internal gaps in Class II (MOD) cavities. Significantly good adaptation was achieved when the setting expansion was 0.87% and greater (p < 0.05).

Analysis of Variance↗
PubMed2003

Intraspecific phylogeny of the New Zealand short-tailed bat Mystacina tuberculata inferred from multiple mitochondrial gene sequences.

An intraspecific phylogeny was established for the New Zealand short-tailed bat Mystacina tuberculata using a 2,878-bp sequence alignment from multiple mitochondrial genes (control region, ND2, 12S ribosomal RNA [rRNA], 16S rRNA, and tRNA). The inferred phylogeny comprises six lineages, with estimated divergences extending back between 0.93 and 0.68 million years to the middle Pleistocene. The lineages do not correspond to the existing subspecific taxonomy. Although multiple lineages occur sympatrically in many populations, the lineages are geographically structured. This structure has persisted despite repeated cycles of range expansion and contraction in response to climatic oscillations and catastrophic volcanic eruptions. The distribution of lineages among populations in central North Island indicates that a hybrid zone was formed by simultaneous colonization from single-lineage source populations inhabiting remote forest refugia. The observed pattern is not typical of microbats, which because of their high mobility generally exhibit low levels of genetic differentiation and geographic structure over continental ranges. Although lineages of M. tuberculata occur sympatrically in many populations, genetic distances between them are sufficiently large to suggest that they may be considered evolutionary significant units or taxonomic subspecies.

Animals↗
PubMed1999

CAG repeat instability, cryptic sequence variation and pathogeneticity: evidence from different loci.

Different aspects of expanded polyglutamine tracts and of their pathogenetic role are taken into consideration here. (i) The (CAG)n length of wild-type alleles of the Huntington disease gene was analysed in instability-prone tumour tissue from colon cancer patients to test whether the process leading to the elongation of alleles towards the expansion range involves single-unit stepwise mutations or larger jumps. The analysis showed that length changes of a single unit had a relatively low frequency. (ii) The observation of an expanded spinocerebellar ataxia (SCA)1 allele with an unusual pattern of multiple CAT interruptions showed that cryptic sequence variations are critical not only for sequence length stability but also for the expression of the disease phenotype. (iii) Small expansions of the (CAG)n sequence at the CACNA1A gene have been reported as causing SCA6. The analysis of families with SCA6 and episodic ataxia type 2 showed that these phenotypes are, in fact, expressions of the same disorder caused either by point mutations or by small (CAG)n expansions. A gain of function has been hypothesized for all proteins containing an expanded polyglutamine stretch, including the alpha 1A subunit of the voltage-gated calcium channel type P/Q coded by the CACNA1A gene. Because point mutations at the same gene with similar phenotypic consequences are highly unlikely to have this effect, an alternative common pathogenetic mechanism for all these mutations, including small expansions, can be hypothesized.

Ataxin-1↗
PubMed2004

Phylogeography of Varicorhinus barbatulus (Cyprinidae) in Taiwan based on nucleotide variation of mtDNA and allozymes.

The phylogeographical patterns and population genetic structures of Varicorhinus barbatulus in Taiwan were investigated based on genetic diversity of 34 allozyme loci and nucleotide sequences of 3' end of the cytochrome b gene, tRNA genes, D-loop control region, and the 5' end of the 12S rRNA of mtDNA. Allozyme and mtDNA analyses revealing evident geographical structuring suggest limited gene flow between populations (F(ST)=0.511 and 0.791, respectively). Low genetic variability within populations (P=5.56%; He=0.018) based on allozymes and significantly negative Tajima's D statistics based on mtDNA suggest that most populations in Taiwan may have originated from a small number of founders followed by demographic expansion. The gene genealogy of mtDNA identified six lineages corresponding to major drainages that were separated by the geological barriers due to vicariant events. A minimum spanning network based on nucleotide substitutions reflects divergence from populations of the Miao-li Plateau to northern and southern regions of the island. In contrast to a previous hypothesis that suggests an early invasion to eastern part of Taiwan prior to the lifting of central mountain range some one million years ago, the mtDNA genealogy and molecular dating reveal very recent colonization of the eastern population. Nested clade analyses revealing significant associations between genetic structure and geographical division identify past fragmentation and range expansion as major phylogeographical events that shaped the geographical distribution of this species in Taiwan.

Animals↗
PubMed2002

Phylogeny of Gaertnera Lam. (Rubiaceae) based on multiple DNA markers: evidence of a rapid radiation in a widespread, morphologically diverse genus.

Phylogenetic relationships among 28 of the 68 species of the paleotropical genus Gaertnera (Rubiaceae) and two related genera were inferred from nucleotide sequence variation in four nuclear DNA (nDNA) markers: the internal transcribed spacers of nuclear rDNA (ITS), the large and small copies of phosphoenolpyruvate carboxylase (PepC-large and PepC-small), and triose phosphate isomerase (Tpi). Phylogenetic analysis of the combined nDNA dataset suggested that Gaertnera is monophyletic, but genetic variation among species was insufficient to reconstruct well-supported relationships within the genus. This was counter to expectations based on the very distinct morphologies and widespread distribution of the genus (West Africa to Sulawesi). Molecular clock analyses suggested variable dates of origin for Gaertnera depending upon the calibration method used. The most plausible calibration implies that Gaertnera migrated to Africa during the early Tertiary, possibly via a boreotropical land bridge and suggests that Gaertnera started to radiate 5.21 +/- 0.14 million years ago. This implies that range expansion in the group has occurred via a number of long-distance dispersal events rather than vicariance. The molecular clock estimate in turn estimated an unusually rapid lineage diversification rate within the radiation of 0.717-0.832 species/million years, comparable to those estimated for radiations on oceanic islands. Although low interspecific competition levels may have contributed to the diversification of Gaertnera on Mauritius, the mechanisms driving the rapid radiation of the group in other parts of its range remain elusive.

Base Sequence↗
PubMed1992

Hormonal and plasma volume alterations following endurance exercise. A brief review.

Plasma volume expansion usually occurs with acute endurance exercise and endurance training both in humans and in animals. In most cases, the increase in plasma volume is associated with lower haematocrit without red cell mass change or an actual reduction in red cell mass, causing relative or true anaemia, respectively. The combination of exercise and heat acclimation (which produces also hypervolaemia, but at a lesser degree than exercise) enhances hypervolaemia induced by exercise training alone. The onset of the phenomenon is extremely rapid: hypervolaemia is observed within minutes or hours of the cessation of exercise. However, 2 days are necessary to reach peak plasma volume expansion after a marathon run or longer race. The magnitude of this natural expansion ranges from 9 to 25%, corresponding to an additional 300 to 700 ml of plasma. The magnitude of this alteration depends on preceding exercise: ambient conditions, intensity and duration of exercise, body posture and frequency of the exercise bouts. The larger the reduction in plasma volume during exercise, the greater the subsequent hypervolaemia. The hydration status of the subjects before and during exercise might modify also plasma volume changes: sufficient fluid ingestion can lead to plasma volume expansion even during prolonged exercise. Fluid-regulating hormones (aldosterone, arginine vasopressin and atrial natriuretic factor) in conjunction with an elevation in plasma protein content promote hypervolaemia. However, the role and the mechanism of the increase in protein mass remain unclear and the hormonal role in the induction of chronic hypervolaemia is still an open question. Hypervolaemia can improve performance by inducing better muscle perfusion, and by increasing stroke volume and maximal cardiac output. By increasing skin blood flow, plasma volume expansion also enhances thermoregulatory responses to exercise. This leads to the important concept of optimal plasma volume and haematocrit, and performance.

Adaptation, Physiological↗
PubMed2006

Molecular genetic variation of boll weevil populations in North America estimated with microsatellites: implications for patterns of dispersal.

The boll weevil (Anthonomus grandis Boheman) is an insect pest of cotton that underwent a well-documented range expansion across the southeastern U.S. from Mexico beginning about 110 years ago. Eleven microsatellite loci were surveyed to infer the magnitude and pattern of genetic differentiation among boll weevil populations from 18 locations across eight U.S. states and northeast Mexico. Estimates of genetic diversity (allelic diversity and heterozygosity) were greater in Southern than Northern populations, and were greater in the west than the east among Northern populations. Boll weevil populations were genetically structured as a whole across the geographic range sampled, with a global F (ST) of 0.241. South-central populations exhibit classic isolation by distance, but evidence suggests that populations within the Eastern and Western regions have not yet reached genetic equilibrium. Gene flow appears to be relatively high among populations within the Eastern region. Population assignment data and estimates of gene flow indicate that migration between locations separated by < 300 km is frequent. The database of microsatellite genotypes generated in this study now makes it possible, through population assignment techniques, to identify the most likely geographic source of a boll weevil reintroduced to an eradication zone, which will help action agencies decide the most appropriate mitigation response.

Animal Migration↗
PubMed2004

Phylogeny and phylogeography of the Liolaemus darwinii complex (Squamata: Liolaemidae): evidence for introgression and incomplete lineage sorting.

Although mitochondrial DNA markers have several properties that make them suitable for phylogeographic studies, they are not free of difficulties. Phylogeographic inferences within and between closely related species can be mislead by introgression and retention of ancestral polymorphism. Here we combine different phylogenetic, phylogeographic, and population genetic methods to extract the maximum information from the Liolaemus darwinii complex. We estimate the phylogeographic structure of L. darwinii across most of its distributional range, and we then estimate relationships between L. darwinii and the syntopic species L. laurenti and L. grosseorum. Our results suggest that range expansion of these lineages brought them into secondary contact in areas where they are presently in syntopy. Here we present the first evidence for introgression in lizards from temperate South America (of L. danwinii mitochondrial DNA into L. laurenti and L. grosseorum), and for incomplete lineage sorting (between L. darwinii and L. laurenti). We show that a combination of methods can provide additional support for inferences derived from any single method and thus provide more robust interpretations and narrow the range of plausible hypotheses about mechanisms and processes of divergence. Additional studies are needed in this group of lizards and in other codistributed groups to determine if Pleistocene climatic changes could be a general factor influencing the evolutionary history of a regional biota.

Animals↗
PubMed2006

Distribution of Assamese macaques (Macaca assamensis) in the inner Himalayan region of Bhutan and their mtDNA diversity.

The distributions of Assamese macaques (Macaca assamensis) and rhesus macaques (M. mulatta) in Bhutan have been only partially documented. In order to investigate the distribution patterns of these species, we conducted field observation and genetic assessment with mitochondrial DNA (mtDNA) typing of macaques in the Inner Himalayas of Bhutan. There were 24 sightings of macaque groups, and all were visually identified as Assamese macaques. No groups of rhesus macaques were sighted in this survey area, in contrast with the survey results in the Nepalese Himalayas. Molecular phylogenetic analysis revealed that the Bhutan macaques are closer in proximity to their counterparts in the Indo-Chinese region (Thailand and Laos) than to rhesus macaques in China, Laos and India. However, clustering results suggested the marked differentiation of the macaques in Bhutan from the Assamese macaques in Indo-China. We tentatively conclude that the macaques of the Inner Himalayan regions in Bhutan are Assamese macaques and that they appear to be of a lineage distinct from Assamese macaques in the Indo-Chinese region (subspecies M. a. assamensis). The degree of mtDNA diversity suggests that the Assamese macaques in Bhutan are of a more ancient ancestry than M. a. assamensis, thereby supporting the speciation hypothesis of the expansion of a sinica-group of macaques from South Asia to Southeast and then to East Asia (Fooden; Fieldiana Zool 45:1-44, 1988). Assignment of Assamese macaques in Bhutan to M. a. pelops is premature due to the lack of molecular data and recent taxonomic controversy. The mtDNA diversity of Assamese macaques was greater than that of rhesus macaques, suggesting the earlier speciation of Assamese macaques. The significance of the ecogeographic segregation model of macaque distribution is discussed in relation to the evolutionary range expansion into the Himalayan regions in South Asia.

Animals↗
PubMed2002

Testing for genetic evidence of population expansion and contraction: an empirical analysis of microsatellite DNA variation using a hierarchical Bayesian model.

The role of past climatic change in shaping the distributions of tropical rain forest vertebrates is central to long-standing hypotheses about the legacy of the Quaternary ice ages. One approach to testing such hypotheses is to use genetic data to infer the demographic history of codistributed species. Population genetic theory that relates the structure of allelic genealogies to historical changes in effective population size can be used to detect a past history of demographic expansion or contraction. The fruit bats Cynopterus sphinx and C. brachyotis (Chiroptera: Pteropodidae) exhibit markedly different distribution patterns across the Indomalayan region and therefore represent an exemplary species pair to use for such tests. The purpose of this study was to test alternative hypotheses about historical patterns of demographic expansion and contraction in C. sphinx and C. brachyotis using a coalescent-based analysis of microsatellite variation. Specifically, we used a hierarchical Bayesian model based on Markov chain Monte Carlo simulations to estimate the posterior distribution of genealogical and demographic parameters. The results revealed strong evidence for population contraction in both species. Evidence for a population contraction in C. brachyotis was expected on the basis of biogeographic considerations. However, similar evidence for population contraction in C. sphinx does not support the hypothesis that this species underwent a pronounced range expansion during the late Quaternary. Genetic evidence for population decline may reflect the consequences of habitat destruction on a more recent time scale.

Animals↗
PubMed2002

Not as the crow flies: a historical explanation for circuitous migration in Swainson's thrush (Catharus ustulatus).

Many migratory songbirds follow circuitous migratory routes instead of taking the shortest path between overwintering and breeding areas. Here, we study the migration patterns in Swainson's thrush (Catharus ustulatus), a neartic-neotropical migrant songbird, using molecular genetic approaches. This species is presently separated into genetically distinct coastal and continental populations that diverged during the Late Pleistocene (as indicated by molecular dating), yet appear to have retained ancestral patterns of migration. Low nucleotide diversity, a star-like haplotype phylogeny and unimodal mismatch distributions all support the hypothesis that both the coastal and the continental populations have undergone recent demographic expansions. Nearctic-neotropical banding and genetic data show nearly complete segregation of migratory routes and of overwintering locations: coastal populations migrate along the Pacific Coast to overwintering sites in Central America and Mexico, whereas continental populations migrate along an eastern route to overwintering sites in Panama and South America. Nearctic-neotropical banding data also show that continental birds north, northwest and east of this migratory divide fly thousands of miles east before turning south. We conclude that circuitous migration in the Swainson's thrush is an artefact of a Late Pleistocene range expansion.

Animal Migration↗
PubMed2005

The effect of the Neolithic expansion on European molecular diversity.

We performed extensive and realistic simulations of the colonization process of Europe by Neolithic farmers, as well as their potential admixture and competition with local Palaeolithic hunter-gatherers. We find that minute amounts of gene flow between Palaeolithic and Neolithic populations should lead to a massive Palaeolithic contribution to the current gene pool of Europeans. This large Palaeolithic contribution is not expected under the demic diffusion (DD) model, which postulates that agriculture diffused over Europe by a massive migration of individuals from the Near East. However, genetic evidence in favour of this model mainly consisted in the observation of allele frequency clines over Europe, which are shown here to be equally probable under a pure DD or a pure acculturation model. The examination of the consequence of range expansions on single nucleotide polymorphism (SNP) diversity reveals that an ascertainment bias consisting of selecting SNPs with high frequencies will promote the observation of genetic clines (which are not expected for random SNPs) and will lead to multimodal mismatch distributions. We conclude that the different patterns of molecular diversity observed for Y chromosome and mitochondrial DNA can be at least partly owing to an ascertainment bias when selecting Y chromosome SNPs for studying European populations.

Chromosomes, Human, Y↗
PubMed1997

Activated long-term peripheral blood cultures as preparation for adoptive alloreactive cell therapy in cancer patients.

Different modes of in vitro activation of peripheral blood mononuclear cells (PBMC) were compared for their effect on long-term propagation. PBMC cultures were activated by short exposures to the mitogen phytohemagglutinin (PHA) and the CD3 complex, with or without secondary signals provided by ligands of CD28 costimulatory molecules. Activation and long-term cultures were carried out in the presence of recombinant interleukin-2 (rIL-2). Addition of supernatant derived from IL-2-activated PBMC improved culture cell yield. Cumulative fold expansions ranged between 10(3) and 10(5) within 21 days. The highest cell yield was found after PHA activation. Fewer cells were obtained after activation with a combination of CD3 and CD28, and even fewer were obtained after CD3 activation alone. An increase in CD8+ and CD56+ cells, without change in CD4+ cells, was found in activated cultures when compared with fresh PBMC. Non-MHC-restricted cytotoxic activity was documented in all activated cultures. Cytotoxic activity per culture was highest in PHA-activated PBMC because of the high cell yield on the day of harvest. Successful in vitro expansion of PBMC might be helpful for gene transfer into T lymphocytes, as well as for the induction of an antitumor response, particularly for prevention and treatment of relapse of hematologic malignancies following allogeneic or autologous bone marrow transplantation.

CD28 Antigens↗
PubMed2003

Genetic consequences of the ice ages on nurseries of the bat Myotis myotis: a mitochondrial and nuclear survey.

Analyses of mitochondrial DNA (mtDNA) control region polymorphism and of variation at 10 nuclear microsatellite loci were used to investigate the mechanisms and genetic consequences of postglacial expansion of Myotis myotis in Europe. Initial sampling consisted of 480 bats genotyped in 24 nursery colonies arranged along a transect of approximately 3000 km. The phylogeographical survey based on mtDNA sequences revealed the existence of major genetic subdivisions across this area, with several suture zones between haplogroups. Such zones of secondary contact were found in the Alps and Rhodopes, whereas other potential barriers to gene flow, like the Pyrenees, did not coincide with genetic discontinuities. Areas of population admixture increased locally the genetic diversity of colonies, which confounded the northward decrease in nucleotide diversity predicted using classical models of postglacial range expansion. However, when analyses were restricted to a subset of 15 nurseries originating from a single presumed glacial refugium, mtDNA polymorphism did indeed support a northwards decrease in diversity. Populations were also highly structured (PhiST = 0.384). Conversely, the same subset of colonies showed no significant latitudinal decrease in microsatellite diversity and much less population structure (FST = 0.010), but pairwise genetic differentiation at these nuclear markers was strongly correlated with increasing geographical distance. Together, this evidence suggests that alleles carried via male bats have maintained enough nuclear gene flow to counteract the effects of recurrent bottlenecks generally associated with recolonization processes. As females are highly philopatric, we argue that the maternally transmitted mtDNA marker better reflects the situation of past, historical gene flow, whereas current levels of gene flow are better reflected by microsatellite markers.

Animals↗