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Source Populations (source + population)
Selected AbstractsSource population of dispersing rock-wallabies (Petrogale lateralis) idengified by assignment tests on multilocus genotypic dataMOLECULAR ECOLOGY, Issue 12 2001M. D. B. Eldridge Abstract The ability to confidently idengify or exclude a population as the source of an individual has numerous powerful applications in molecular ecology. Several alternative assignment methods have recently been developed and are yet to be fully evaluated with empirical data. In this study we tested the efficacy of different assignment methods by using a translocated rock-wallaby (Petrogale lateralis) population, of known provenance. Specimens from the translocated population (n = 43), its known source population (n = 30) and four other nearby populations (n = 19,32) were genotyped for 11 polymorphic microsatellite loci. The results idengified Bayesian clustering, frequency and Bayesian methods as the most consistent and accurate, correctly assigning 93,100% of individuals up to a significance threshold of P = 0.01. Performance was variable among the distance-based methods, with the Cavalli-Sforza and Edwards chord distance performing best, whereas Goldstein et al.'s (,µ)2 consistently performed poorly. Using Bayesian clustering, frequency and Bayesian methods we then attempted to determine the source of rock-wallabies which have recently recolonized an outcrop (Gardners) 8 km from the nearest rock-wallaby population. Results indicate that the population at Gardners originated via a recent dispersal event from the eastern end of Mt. Caroline. This is only the second published record of dispersal by rock-wallabies between habitat patches and is the longest movement recorded to date. Molecular techniques and methods of analysis are now available to allow detailed studies of dispersal in rock-wallabies and should also be possible for many other taxa. [source] Source populations in carnivore management: cougar demography and emigration in a lightly hunted populationANIMAL CONSERVATION, Issue 4 2009H. S. Cooley Abstract Wildlife agencies typically attempt to manage carnivore numbers in localized game management units through hunting, and do not always consider the potential influences of immigration and emigration on the outcome of those hunting practices. However, such a closed population structure may not be an appropriate model for management of carnivore populations where immigration and emigration are important population parameters. The closed population hypothesis predicts that high hunting mortality will reduce numbers and densities of carnivores and that low hunting mortality will increase numbers and densities. By contrast, the open population hypothesis predicts that high hunting mortality may not reduce carnivore densities because of compensatory immigration, and low hunting mortality may not result in more carnivores because of compensatory emigration. Previous research supported the open population hypothesis with high immigration rates in a heavily hunted (hunting mortality rate=0.24) cougar population in northern Washington. We test the open population hypothesis and high emigration rates in a lightly hunted (hunting mortality rate=0.11) cougar population in central Washington by monitoring demography from 2002 to 2007. We used a dual sex survival/fecundity Leslie matrix to estimate closed population growth and annual census counts to estimate open population growth. The observed open population growth rate of 0.98 was lower than the closed survival/fecundity growth rates of 1.13 (deterministic) and 1.10 (stochastic), and suggests a 12,15% annual emigration rate. Our data support the open population hypothesis for lightly hunted populations of carnivores. Low hunting mortality did not result in increased numbers and densities of cougars, as commonly believed because of compensatory emigration. [source] Long-distance dispersal of seeds in the fire-tolerant shrub Banksia attenuataECOGRAPHY, Issue 4 2009Tianhua He Long-distance dispersal (LDD) of seeds enables alleles, individuals and species of plants to (re)colonize suitable but remote habitats. Banksia attenuata is a long-lived resprouting shrub restricted to dune crests in fire-prone sclerophyll shrublands of the Eneabba sandplain, southwestern Australia. Highly polymorphic microsatellite DNA genetic markers and population assignment tests were employed to identify LDD immigrants among 788 individuals from 27 stands of B. attenuata comprising a metapopulation. Of the 487 (61.8% of the total) individuals unambiguously assigned to a unique source population, 27 (5.5%) were identified as immigrants by assignment to a known population other than that from which they were sampled, while the remaining 460 were assigned to the population from which they were sampled. The distance between source and sink populations for these immigrants ranged from 0.2 to 2.6,km, averaging 1.4,km, and broadly trending in the direction of seasonal winds. These results suggest that B. attenuata has similar long-distance seed dispersal properties as its co-occurring shorter-lived and fire-sensitive congener, B. hookeriana, despite fewer, larger and less mobile seeds. The frequency and distance of LDD for seeds observed in both species (5.5,6.8%) helps explain the persistence of populations on these geographically isolated dunes, where they are subject to local extinction from recurrent fire and severe summer drought, and will remain important under predicted climate change conditions. Analysis also revealed that species richness of the functional group to which B. attenuata belongs was positively correlated with the number of immigrants identified per dune, and such correlation was likely driven by environmental properties of the dunes, particularly water availability. [source] Patch occupancy, population density and dynamics in a fragmented red squirrel Sciurusvulgaris populationECOGRAPHY, Issue 1 2003Goedele Verbeylen We studied population dynamics of red squirrels in a group of small forest fragments, that cover only 6.5% of the total study area (4664 ha) and where distances to the nearest source population were up to 2.2 km. We tested effects of patch size, quality and isolation and supplementary feeding on patch occupation during 1995,99. Larger patches and patches with supplementary feeding had a higher probability of being occupied. No patch <3.5 ha was ever occupied. No effects of isolation were found, suggesting that the forest habitat in the study area is not sufficiently fragmented to influence red squirrel distribution across patches. For medium sized patches (3.7,21 ha), that were occupied some years, there was an increase in patch occupation over the years, even though overall population size tended to decrease. These patches had a high turnover, especially of males. Patches in which the squirrel population went extinct were recolonized within a year. For patches that were at least some years occupied, squirrel density depended on patch quality only. No effects of patch size, isolation and winter temperature on population density were found. These data suggest that in our study area habitat fragmentation has no effect on local squirrel density and that the random sample hypothesis explains the distribution pattern across patches. [source] Sexual selection did not contribute to the evolution of male lifespan under curtailed age at reproduction in a seed beetleECOLOGICAL ENTOMOLOGY, Issue 5 2009ALEXEI A. MAKLAKOV Abstract. 1. Sexual selection is a powerful evolutionary force that is hypothesised to play an important role in the evolution of lifespan. Here we test for the potential contribution of sexual selection to the rapid evolution of male lifespan in replicated laboratory populations of the seed beetle, Callosobruchus maculatus. 2. For 35 generations, newly hatched virgin male beetles from eight different populations were allowed to mate for 24 h and then discarded. Sexual selection was removed in half of these populations by enforcing random monogamy. 3. Classic theory predicts that because of sexual competition, males from sexually selected lines would have higher age-specific mortality rates and shorter lifespan than males from monogamous lines. 4. Alternatively, condition-dependent sexual selection may also favour genes that have positive pleiotropic effects on lifespan and ageing. 5. Males from all eight populations evolved shorter lifespans compared with the source population. However, there was no difference in lifespan between males from populations with or without sexual selection. Thus, sexual selection did not contribute to the evolution of male lifespan despite the fact that such evolution did occur in our study populations. [source] Consequences for a host,parasitoid interaction of host-plant aggregation, isolation, and phenologyECOLOGICAL ENTOMOLOGY, Issue 4 2007ADAM J. VANBERGEN Abstract 1.,Spatial habitat structure can influence the likelihood of patch colonisation by dispersing individuals, and this likelihood may differ according to trophic position, potentially leading to a refuge from parasitism for hosts. 2.,Whether habitat patch size, isolation, and host-plant heterogeneity differentially affected host and parasitoid abundance, and parasitism rates was tested using a tri-trophic thistle,herbivore,parasitoid system. 3.,Cirsium palustre thistles (n= 240) were transplanted in 24 blocks replicated in two sites, creating a range of habitat patch sizes at increasing distance from a pre-existing source population. Plant architecture and phenological stage were measured for each plant and the numbers of the herbivore Tephritis conura and parasitoid Pteromalus elevatus recorded. 4.,Mean herbivore numbers per plant increased with host-plant density per patch, but parasitoid numbers and parasitism rates were unaffected. Patch distance from the source population did not influence insect abundance or parasitism rates. Parasitoid abundance was positively correlated with host insect number, and parasitism rates were negatively density dependent. Host-plant phenological stage was positively correlated with herbivore and parasitoid abundance, and parasitism rates at both patch and host-plant scales. 5.,The differential response between herbivore and parasitoid to host-plant density did not lead to a spatial refuge but may have contributed to the observed parasitism rates being negatively density dependent. Heterogeneity in patch quality, mediated by variation in host-plant phenology, was more important than spatial habitat structure for both the herbivore and parasitoid populations, and for parasitism rates. [source] DIFFERENTIAL PERFORMANCE AMONG LDH-B GENOTYPES IN RANA LESSONAE TADPOLESEVOLUTION, Issue 5 2000Hansjürg Hotz Abstract The European pool frog, Rana lessonae, is widely polymorphic for two common alleles (b, e) at the lactate dehydrogenase-B (LDH-B) locus. We compared fitness-related larval life-history traits among LDH-B genotypes, which originated from segregation in heterozygous parents, in an artificial pond experiment where tadpoles of R. lessonae from a Swiss population were raised together with tadpoles of the hemiclonal hybrid R. esculenta at two densities. In R. lessonae, LDH-B e/e homozygotes at each density had a higher proportion of metamorphs among survivors, reached metamorphosis earlier, and were heavier at metamorphosis than b/b homozygotes; b/e heterozygotes had intermediate values. That e/e individuals were superior to b/b in both time to and mass at metamorphosis is surprising because these two life-history traits are thought to reflect a performance trade-off; e/e genotypes apparently compensated for shorter time to metamorphosis by a higher growth rate. The two alleles showed the same performance ranking when combined in hybrids with a R. ridibunda allele: When R. esculenta from Swiss populations reared in the same ponds had received the e allele rather than the b allele from their R. lessonae parent, they reached metamorphosis earlier, but did not differ in mass at metamorphosis. The degree of linkage disequilibrium in the source population of the eight R. lessonae used as parents of the R. lessonae tadpoles is unknown, so we cannot exclude the possibility that the performance differences are caused by some anonymous tightly linked gene, rather than the LDH-B locus, that constitutes the genomically localized target of natural selection. A causal involvement of LDH-B is plausible, nevertheless, because this enzyme takes part in the central energy-metabolizing processes and has been reported to underlie fitness differences in other animals; also, differential performance of LDH-B genotypes has been observed in R. lessonae larvae from another population. The present results suggest strong directional selection for allele e; the sum of available data, including an independent laboratory experiment, suggests that partial environment-dependent overdominance combined with balancing selection favoring e/e homozygotes under some and b/b homozygotes under other conditions may be partially responsible for the broad maintenance of the LDH-B polymorphism in R. lessonae. [source] Breaking taboos in the tropics: incest promotes colonization by wood-boring beetlesGLOBAL ECOLOGY, Issue 4 2001Bjarte H. Jordal Abstract 1,Inbreeding and parthenogenesis are especially frequent in colonizing species of plants and animals, and inbreeding in wood-boring species in the weevil families Scolytinae and Platypodidae is especially common on small islands. In order to study the relationship between colonization success, island attributes and mating system in these beetles, we analysed the relative proportions of inbreeders and outbreeders for 45 Pacific and Old World tropical islands plus two adjacent mainland sites, and scored islands for size, distance from nearest source population, and maximum altitude. 2,The numbers of wood-borer species decreased with decreasing island size, as expected; the degree of isolation and maximum island altitude had negligible effects on total species numbers. 3,Numbers of outbreeding species decreased more rapidly with island size than did those of inbreeders. Comparing species with similar ecology (e.g. ambrosia beetles) showed that this difference was best explained by differential success in colonization, rather than by differences in resource utilization or sampling biases. This conclusion was further supported by analyses of data from small islands, which suggested that outbreeding species have a higher degree of endemism and that inbreeding species are generally more widespread. 4,Recently established small populations necessarily go through a period of severe inbreeding, which should affect inbreeding species much less than outbreeding ones. In addition, non-genetic ecological and behavioural (,Allee') effects are also expected to reduce the success of outbreeding colonists much more than that of inbreeders: compared with inbreeders, outbreeders are expected to have slower growth rates, have greater difficulties with mate-location and be vulnerable to random extinction over a longer period. [source] The establishment of an urban bird populationJOURNAL OF ANIMAL ECOLOGY, Issue 5 2008Christian Rutz Summary 1Despite the accelerating global spread of urbanized habitats and its associated implications for wildlife and humans, surprisingly little is known about the biology of urban ecosystems. 2Using data from a 60-year study period, this paper provides a detailed description of how the northern goshawk Accipiter gentilis L. , generally considered a shy forest species , colonized the city of Hamburg, Germany. Six non-mutually exclusive hypotheses are investigated regarding the environmental factors that may have triggered this invasion. 3The spatio-temporal analysis of 2556 goshawk chance observations (extracted from a total data set of 1 174 493 bird observations; 1946,2003) showed that hawks regularly visited the city centre decades before the first successful breeding attempts were recorded. Many observations were made in parts of the city where territories were established in later years, demonstrating that these early visitors had encountered, but not used, potential nest sites. 4Pioneer settlement coincided with: (i) an increase in (legal) hunting pressure on goshawks in nearby rural areas; (ii) an increase in avian prey abundance in the city; and (iii) a succession of severe winters in the Greater Hamburg area. On the other hand, there was no evidence to suggest that the early stages of the invasion were due to: (i) decreasing food availability in rural areas; (ii) major habitat changes in the city; or (iii) rural intraguild dynamics forcing hawks into urban refugia. While breeding numbers of a potential rural source population were at a long-term low when the city was colonized, prior to first settlement there was a sharp increase of goshawk chance observations in the city and its rural periphery. 5The urban population expanded rapidly, and pair numbers began to stabilize after about 10 years. Ringing data (219 ringed nestlings from 70 urban broods; 1996,2000) demonstrated that most urban recruits had fledged in the city, but also confirmed considerable gene flow between urban and rural habitats. Analysis of chance observations (as raw data or as detrended time series) suggested a tight coupling of population dynamics inside and outside the city. 6City-colonizations such as the one described here provide a valuable opportunity to study some fundamental aspects of population ecology on a scale at which detailed monitoring is logistically feasible. Furthermore, a good understanding of urban ecology has become essential for efficient wildlife conservation in modern, human-altered environments. [source] Lessepsian fish migration: genetic bottlenecks and parasitological evidenceJOURNAL OF BIOGEOGRAPHY, Issue 5 2010Paolo Merella Abstract As a rule, non-indigenous species (NIS) populations derived from biological invasion events represent a subset of the genetic diversity of the source population. In biological invasions, host,parasite interactions play an important role, and parasitological data for NIS populations can provide useful information such as their area of origin, mechanism of invasion and prospects of success in the new habitat. When both genetic and parasitological data are available, and they suggest the same scenario, the history of an invasion can be inferred with no discrepancy, but when data cannot be reconciled an alternative model should be considered. In this study a comparison of genetic and parasitological data for the Lessepsian migrant the bluespotted cornetfish, Fistularia commersonii, in the Mediterranean Sea presents the opportunity to evaluate the compatibility of information of this nature, and to propose possible invasion scenarios consistent with evidence provided by both criteria. [source] Historic and contemporary levels of genetic variation in two New Zealand passerines with different histories of declineJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2007S. S. TAYLOR Abstract We compared historic and contemporary genetic variation in two threatened New Zealand birds (saddlebacks and robins) with disparate bottleneck histories. Saddlebacks showed massive loss of genetic variation when extirpated from the mainland, but no significant loss of variation following a severe bottleneck in the 1960s when the last population was reduced from ,1000 to 36 birds. Low genetic variation was probably characteristic of this isolated island population: considerably more genetic variation would exist in saddlebacks today if a mainland population had survived. In contrast to saddlebacks, contemporary robin populations showed only a small decrease in genetic variation compared with historical populations. Genetic variation in robins was probably maintained because of their superior ability to disperse and coexist with introduced predators. These results demonstrate that contemporary genetic variation may depend more greatly on the nature of the source population and its genetic past than it does on recent bottlenecks. [source] Morphological divergence and origin of sympatric populations of European whitefish (Coregonus lavaretus L.) in Lake Femund, NorwayJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2005K. ØSTBYE Abstract Combining morphological and genetic analysis, we compared patterns of diversification within and between morphs among sympatric European whitefish (Coregonus lavaretus L.) populations in Lake Femund, Norway. Seven external populations, from potential colonization routes into Lake Femund were included. We found that deep-, shallow-, river- and bay spawning populations are distinct morphs in Lake Femund. Within morphs, populations range from being similar genetically (Fst = 0,0.005) among deep-spawning populations to being highly differentiated (Fst = 0.153) between bay-spawning populations. Between morphs, genetic differences ranged from a low (Fst = 0.008,0.022) between deep- and shallow-spawning populations to high difference (Fst = 0.125,0.143) between shallow- and bay-spawning populations. A higher proportion of molecular variance was seen among (3.9%) than within morphs (2.8%). The adaptive gene combinations behind the four morphs seem to have originated within the lake, although the lake could have been colonized from more than one source population. [source] The genetic stock structure of larval and juvenile winter flounder larvae in Connecticut waters of eastern Long Island Sound and estimations of larval entrainmentJOURNAL OF FISH BIOLOGY, Issue 1 2004J. F. Crivello Variability at six microsatellite loci was examined among 536 winter flounder Pseudopleuronectes americanus larvae collected from three locations in eastern Long Island Sound shown to be nursery areas for the species. Substantial genetic differences were seen among the putative source populations and thus appeared to be geographically based. These differences were used to characterize the most likely sources of winter flounder larvae entrained at the Millstone Power Station as well as recruitment to juvenile winter flounder collected in the Niantic River. Samples were classified to the most likely geographical source population both by a conditional maximum likelihood method and by a multi-layer feed-forward neural net trained on the differences in microsatellite allele frequencies. The classification of samples by both methods is compared and discussed in the context of winter flounder management. [source] Is the large size of the pinna of the ear of the European hare (Lepus europaeus) due to its role in thermoregulation or in anterior capital shock absorption?JOURNAL OF MORPHOLOGY, Issue 6 2010Philip Stott Abstract Large pinnae are characteristic of the Leporids, and the pinna is known to have a thermoregulatory role. Another role has been hypothesized for the pinna of Lepus spp., as a part of a suspensory system for the greater portion of the head, absorbing shock that might otherwise interfere with vision during high-speed locomotion. We compared the lengths of the pinnae of adult European hares Lepus europaeus from the source population in the cooler climate of England with those of the introduced population in the warmer climate of Australia, and we compared the lengths of the pinnae of hares that had grown in cooler weather with those that had grown in warmer weather. There were no significant differences between each of the comparisons, indicating that the size of the pinna is not determined by thermoregulatory requirements at rest. We compared the growth in length of the pinnae and the legs with growth in body mass, and growth in the mass of the pinnae with the masses of the head and the eyeballs, and found support for the suspension hypothesis. We suggest that the rapid growth of the pinna is because visual acuity is a function of absolute eye size, not relative eye size, yet juvenile hares are subject to the same predator pressure as adult hares, and equally need to maximize visual acuity while running at high speeds in dim light. We believe that the large size of the pinna is determined by its role in anterior capital suspension, not in thermoregulation. J. Morphol., 2010. © 2010 Wiley-Liss, Inc. [source] Inferring colonization history and dispersal patterns of a long-lived seabird by combining genetic and empirical dataJOURNAL OF ZOOLOGY, Issue 4 2010L. C. Young Abstract Identifying biological trends and threats to organisms that make long distance migrations are often the limiting factors in their conservation. Indeed, Laysan albatross Phoebastria immutabilis are highly vagile seabirds, foraging throughout the North Pacific Ocean. Despite mark,recapture data indicating natal philopatry, Laysan albatross recently re-colonized several anthropogenically extirpated breeding locations. At the same time, a breeding population in the north-western Hawaiian Islands was lost to erosion and it was hypothesized that the colonization events were due to displacement rather than dispersal. Nuclear and mitochondrial markers were used in a range wide survey to test whether natal philopatry corresponded to population structure in Laysan albatross, and to determine whether recent colonization events were a result of displacement from vanishing breeding habitat. Five microsatellite loci found little population structure (FST=0.01, P=0.001), and sequences from the mitochondrial control region revealed low population structure (,ST=0.05, P<0.001). The results were consistent with male-mediated dispersal and strong, but not absolute, philopatry by females. Mixed stock analyses and banding records from the newly colonized sites indicated contributions from multiple source populations, which contradicted the displacement hypothesis of a single source population and instead supported species-wide dispersal from all source colonies. High genetic diversity (,=0.045, h=0.989), rapid colonization, and great dispersal potential bode well for the conservation of Laysan albatross. However, it may be necessary to protect high-island nesting sites, preserve genetic diversity and maintain breeding populations in the face of projected sea level rises and persistent bycatch. [source] Mitochondrial and microsatellite DNA markers reveal a Balkan origin for the highly invasive horse-chestnut leaf miner Cameraria ohridella (Lepidoptera, Gracillariidae)MOLECULAR ECOLOGY, Issue 16 2009R. VALADE Abstract Biological invasions usually start with a small number of founder individuals. These founders are likely to represent a small fraction of the total genetic diversity found in the source population. Our study set out to trace genetically the geographical origin of the horse-chestnut leafminer, Cameraria ohridella, an invasive microlepidopteran whose area of origin is still unkown. Since its discovery in Macedonia 25 years ago, this insect has experienced an explosive westward range expansion, progressively colonizing all of Central and Western Europe. We used cytochrome oxidase I sequences (DNA barcode fragment) and a set of six polymorphic microsatellites to assess the genetic variability of C. ohridella populations, and to test the hypothesis that C. ohridella derives from the southern Balkans (Albania, Macedonia and Greece). Analysis of mtDNA of 486 individuals from 88 localities allowed us to identify 25 geographically structured haplotypes. In addition, 480 individuals from 16 populations from Europe and the southern Balkans were genotyped for 6 polymorphic microsatellite loci. High haplotype diversity and low measures of nucleotide diversities including a significantly negative Tajima's D indicate that C. ohridella has experienced rapid population expansion during its dispersal across Europe. Both mtDNA and microsatellites show a reduction in genetic diversity of C. ohridella populations sampled from artificial habitats (e.g. planted trees in public parks, gardens, along roads in urban or sub-urban areas) across Europe compared with C. ohridella sampled in natural stands of horse-chestnuts in the southern Balkans. These findings suggest that European populations of C. ohridella may indeed derive from the southern Balkans. [source] Phylogeography of the greater horseshoe bat, Rhinolophus ferrumequinum: contrasting results from mitochondrial and microsatellite dataMOLECULAR ECOLOGY, Issue 2 2009JON FLANDERS Abstract Phylogeographical studies are typically based on haplotype data, occasionally on nuclear markers such as microsatellites, but rarely combine both. This is unfortunate because the use of markers with contrasting modes of inheritance and rates of evolution might provide a more accurate and comprehensive understanding of a species' history. Here we present a detailed study of the phylogeography of the greater horseshoe bat, Rhinolophus ferrumequinum, using 1098 bp of the mitochondrial ND2 gene from 45 localities from across its Palaearctic range to infer population history. In addition, we re-analysed a large microsatellite data set available for this species and compared the results of both markers to infer population relationships and the historical processes influencing them. We show that mtDNA, the most popular marker in phylogeography studies, yielded a misleading result, and would have led us to conclude erroneously that a single expansion had taken place in Europe. Only by combining the mitochondrial and microsatellite data sets are we able to reconstruct the species' history and show two colonization events in Europe, one before the Last Glacial Maximum (LGM) and one after it. Combining markers also revealed the importance of Asia Minor as an ancient refugium for this species and a source population for the expansion of the greater horseshoe bat into Europe before the LGM. [source] Chloroplast and microsatellite DNA diversities reveal the introduction history of Brazilian peppertree (Schinus terebinthifolius) in FloridaMOLECULAR ECOLOGY, Issue 12 2005DEAN A. WILLIAMS Abstract Brazilian peppertree (Schinus terebinthifolius) is a woody perennial that has invaded much of Florida. This native of northeastern Argentina, Paraguay, and Brazil was brought as an ornamental to both the west and east coasts of Florida at the end of the 19th century. It was recorded as an invader of natural areas in the 1950s, and has since extended its range to cover over 280 000 ha. Our goals were to understand the history of this invasion, as one step toward understanding why this exotic was so successful, and ultimately to improve development of biological control agents. We sampled plants from the native and exotic ranges, particularly Florida, and genotyped these individuals at nuclear and chloroplast loci. Nuclear microsatellite and cpDNA loci reveal strong genetic population structure consistent with limited dispersal in the introduced and native ranges. Bayesian clustering of microsatellite data separates the east and west coast plants in Florida into distinct populations. The two chloroplast haplotypes found in Florida are also concordant with this separation: one predominates on the east coast, the other on the west coast. Analysis of samples collected in South America shows that haplotypes as distinct as the two in Florida are unlikely to have come from a single source population. We conclude that the genetic evidence supports two introductions of Brazilian peppertree into Florida and extensive hybridization between them. The west coast genotype likely came from coastal Brazil at about 27° south, whereas the east coast genotype probably originated from another, as yet unidentified site. As a result of hybridization, the Florida population does not exhibit low genetic variation compared to populations in the native range, possibly increasing its ability to adapt to novel environments. Hybridization also has important consequences for the selection of biocontrol agents since it will not be possible to identify closely co-adapted natural enemies in the native range, necessitating more extensive host testing. [source] Microsatellite variation within and among North American lineages of Phragmites australisMOLECULAR ECOLOGY, Issue 7 2003K. Saltonstall Abstract Over the past century, the spread of the common reed (Phragmites australis) has had a dramatic impact on wetland communities across North America. Although native populations of Phragmites persist, introduced invasive populations have dominated many sites and it is not clear if the two types can interbreed. This study compares patterns of differentiation in 10 microsatellite loci among North American and European Phragmites individuals with results obtained from sequencing of noncoding chloroplast DNA. Three population lineages (native, introduced and Gulf Coast) were previously identified in North America from chloroplast DNA and similar structuring was found in the nuclear genome. Each lineage was distinguished by unique alleles and allele combinations and the introduced lineage was closely related to its hypothesized source population in Europe. Size homoplasy and diagnostic base substitutions distinguishing lineages were evident at several loci, further emphasizing that native, introduced and Gulf Coast North American Phragmites lineages are genetically distinct. Gene flow between lineages was low and invasive introduced populations do not represent a hybrid population type. [source] Source population of dispersing rock-wallabies (Petrogale lateralis) idengified by assignment tests on multilocus genotypic dataMOLECULAR ECOLOGY, Issue 12 2001M. D. B. Eldridge Abstract The ability to confidently idengify or exclude a population as the source of an individual has numerous powerful applications in molecular ecology. Several alternative assignment methods have recently been developed and are yet to be fully evaluated with empirical data. In this study we tested the efficacy of different assignment methods by using a translocated rock-wallaby (Petrogale lateralis) population, of known provenance. Specimens from the translocated population (n = 43), its known source population (n = 30) and four other nearby populations (n = 19,32) were genotyped for 11 polymorphic microsatellite loci. The results idengified Bayesian clustering, frequency and Bayesian methods as the most consistent and accurate, correctly assigning 93,100% of individuals up to a significance threshold of P = 0.01. Performance was variable among the distance-based methods, with the Cavalli-Sforza and Edwards chord distance performing best, whereas Goldstein et al.'s (,µ)2 consistently performed poorly. Using Bayesian clustering, frequency and Bayesian methods we then attempted to determine the source of rock-wallabies which have recently recolonized an outcrop (Gardners) 8 km from the nearest rock-wallaby population. Results indicate that the population at Gardners originated via a recent dispersal event from the eastern end of Mt. Caroline. This is only the second published record of dispersal by rock-wallabies between habitat patches and is the longest movement recorded to date. Molecular techniques and methods of analysis are now available to allow detailed studies of dispersal in rock-wallabies and should also be possible for many other taxa. [source] Phylogenetic analyses of Caulerpa taxifolia (Chlorophyta) and of its associated bacterial microflora provide clues to the origin of the Mediterranean introductionMOLECULAR ECOLOGY, Issue 4 2001I. Meusnier Abstract The accidental introduction of Caulerpa taxifolia into the Mediterranean is no longer under dispute. What has eluded researchers until now, is definitive evidence for the original, biogeographical source population. Here we present two independent lines of evidence that support an Australian origin for the Mediterranean populations of C. taxifolia. First, we reanalysed algal rDNA-internal transcribed spacer (rDNA-ITS) sequences, combining previously published sequences from different studies with 22 new sequences. The ITS sequence comparison showed that the Australian sample is the sister group of the Mediterranean,aquarium clade. Second, cloned bacterial 16S rDNA gene sequences were analysed from the associated microflora of C. taxifolia collected from Australia, Tahiti, the Philippines and the Mediterranean. Five bacterial lineages were identified, of which three were dominant. Alpha Proteobacteria were the most abundant and were found in all samples. In contrast, members of the beta Proteobacterial line and Cytophaga-Flexibacter-Bacteroides line (CFB) were mainly associated with Mediterranean and Australian samples. Frequency distributions of the five bacterial lineages were significantly different among biogeographical locations. Phylogenetic analyses of the 54 bacterial sequences derived from the four C. taxifolia individuals resulted in a well-resolved tree with high bootstrap support. The topologies of the beta Proteobacteria and CFB mirror the geographical sources of their algal hosts. Bacterial,algal associations provide an identification tool that may have wide application for the detection of marine invasions. [source] On cross-correlating weak lensing surveysMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005Dipak Munshi ABSTRACT The present generation of weak lensing surveys will be superseded by surveys run from space with much better sky coverage and high level of signal-to-noise ratio, such as the Supernova/Acceleration Probe (SNAP). However, removal of any systematics or noise will remain a major cause of concern for any weak lensing survey. One of the best ways of spotting any undetected source of systematic noise is to compare surveys that probe the same part of the sky. In this paper we study various measures that are useful in cross-correlating weak lensing surveys with diverse survey strategies. Using two different statistics , the shear components and the aperture mass , we construct a class of estimators which encode such cross-correlations. These techniques will also be useful in studies where the entire source population from a specific survey can be divided into various redshift bins to study cross-correlations among them. We perform a detailed study of the angular size dependence and redshift dependence of these observables and of their sensitivity to the background cosmology. We find that one-point and two-point statistics provide complementary tools which allow one to constrain cosmological parameters and to obtain a simple estimate of the noise of the survey. [source] Multiwavelength study of the nuclei of a volume-limited sample of galaxies , I. X-ray observationsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2000P. Lira We discuss ROSAT HRI X-ray observations of 33 very nearby galaxies, sensitive to X-ray sources down to a luminosity of approximately 1038 erg s,1. The galaxies are selected from a complete, volume-limited sample of 46 galaxies with for which we have extensive multiwavelength data. For an almost complete subsample with (29/31 objects) we have HRI images. Contour maps and source lists are presented within the central region of each galaxy, together with nuclear upper limits where no nuclear source was detected. Nuclear X-ray sources are found to be very common, occurring in ,35 per cent of the sample. Nuclear X-ray luminosity is statistically connected to host galaxy luminosity , there is not a tight correlation, but the probability of a nuclear source being detected increases strongly with galaxy luminosity, and the distribution of nuclear luminosities seems to show an upper envelope that is roughly proportional to galaxy luminosity. While these sources do seem to be a genuinely nuclear phenomenon rather than nuclear examples of the general X-ray source population, it is far from obvious that they are miniature Seyfert nuclei. The more luminous nuclei are very often spatially extended, and H ii region nuclei are detected just as often as LINERs. Finally, we also note the presence of fairly common superluminous X-ray sources in the off-nuclear population , out of 29 galaxies we find nine sources with a luminosity greater than 1039 erg s,1. These show no particular preference for more luminous galaxies. One is already known to be a multiple SNR system, but most have no obvious optical counterpart and their nature remains a mystery. [source] Risk of breast cancer in association with exposure to two different groups of tricyclic antidepressants,PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 10 2006Hani Tamim PhD Abstract Purpose In 2002, we reported an epidemiological study in which we found that some tricyclic antidepressants (identified as genotoxic in Drosophila Melanogaster) were associated with an increased risk of breast cancer, when exposure took place 11,15 years before the date of diagnosis. The implications of the results found lead us to carry out a separate case-control study, using the same source population, to validate the conclusions drawn from our previous study. Methods We accrued 7330 breast cancer cases, diagnosed between 1981 and 2000, and 29,320 controls matched on age and time. Results The association between exposure to genotoxic TCAs 11,15 years before diagnosis and the risk of breast cancer development was much weaker, as compared to what was reported in our previous study. The relative risk of breast cancer in women exposed to high doses of genotoxic TCAs 11,15 years before diagnosis was 1.17 (95%CI: 0.79,1.74), while in women exposed to high levels of non-genotoxic TCAs during the same period it was 0.95 (95%CI: 0.61,1.48). Conclusion In conclusion, we did not find supporting evidence for an increased risk of breast cancer among women exposed to TCAs up to 20 years in the past. Copyright © 2006 John Wiley & Sons, Ltd. [source] Maternal nickel exposure and congenital musculoskeletal defectsAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 11 2008Vaktskjold Arild DrScient Abstract Objective To investigate whether women occupationally exposed to nickel in early pregnancy are at elevated risk of delivering a newborn with a malformation or deformation of the musculoskeletal system (ICD-10: Q65-Q79). Methods Data about the newborn, maternal occupation and workplace were obtained using the Kola Birth Register (KBR). Each record in the KBR was assigned a categorical nickel (Ni) exposure rating according to the occupation the delivering woman had at the time of becoming pregnant. This was achieved by using as a guideline the water-soluble Ni subfraction of the inhalable aerosol fraction obtained by personal monitoring for nickel- and copper-refinery workers or/and measured urinary-Ni concentrations. The reference population was delivering women from the source population with background exposure level. In total, the study population consisted of 22,965 births. Results Three hundred and four infants (13.3/1,000 births; 95% confidence interval (CI): 11.9,14.7) were diagnosed with isolated musculoskeletal defect(s) at birth. The adjusted odds ratio for the association between the maternal exposure to Ni and this outcome was 0.96 (95% CI: 0.76,1.21) per unit increase in exposure category. Conclusion The incidence of defects in the musculoskeletal system at birth was high, especially for feet deformities, but we found no effect of maternal exposure to water-soluble Ni on the risk of delivering a newborn with a defect. However, the incidence among women working in the copper refinery was higher than in the other employment groups. Am. J. Ind. Med. 51:825-833, 2008. © 2008 Wiley-Liss, Inc. [source] Decreased immunocompetence in a severely bottlenecked population of an endemic New Zealand birdANIMAL CONSERVATION, Issue 1 2007K. A. Hale Abstract Inbreeding resulting from severe population bottlenecks may impair an individual's immune system and render it more susceptible to disease. Although a reduced immune response could threaten the survival of highly endangered species, few studies have assessed the effect of population bottlenecks on immunocompetence. We compared the counts of leucocytes and external, blood and gastrointestinal parasite loads in two populations of the endemic New Zealand robin Petroica australis to assess the immunocompetence of birds in a severely bottlenecked population relative to its more genetically diverse source population. Despite similar parasite loads in both populations, robins in the severely bottlenecked population showed lower counts of both total leucocyte and total lymphocyte numbers. When the immune system was experimentally challenged using the phytohaemagglutinin skin test, robins in the severely bottlenecked population exhibited a significantly lower immune response than the source population, suggesting that birds passing through a severe bottleneck have a compromised immunocompetence. Our results confirm that severe bottlenecks reduce the immune response of birds and highlight the need to avoid severe bottlenecks in the recovery programmes of endangered species. [source] Using Case-parent Triads to Estimate Relative Risks Associated with a Candidate HaplotypeANNALS OF HUMAN GENETICS, Issue 3 2009Min Shi Summary Estimating haplotype relative risks in a family-based study is complicated by phase ambiguity and the many parameters needed to quantify relative risks for all possible diplotypes. This problem becomes manageable if a particular haplotype has been implicated previously as relevant to risk. We fit log-linear models to estimate the risks associated with a candidate haplotype relative to the aggregate of other haplotypes. Our approach uses existing haplotype-reconstruction algorithms but requires assumptions about the distribution of haplotypes among triads in the source population. We consider three levels of stringency for those assumptions: Hardy-Weinberg Equilibrium (HWE), random mating, and no assumptions at all. We assessed our method's performance through simulations encompassing a range of risk haplotype frequencies, missing data patterns, and relative risks for either offspring or maternal genetic effects. The unconstrained model provides robustness to bias from population structure but requires excessively large sample sizes unless there are few haplotypes. Assuming HWE accommodates many more haplotypes but sacrifices robustness. The model assuming random mating is intermediate, both in the number of haplotypes it can handle and in robustness. To illustrate, we reanalyze data from a study of orofacial clefts to investigate a 9-SNP candidate haplotype of the IRF6 gene. [source] Combined definition of seed transfer guidelines for ecological restoration in the French PyreneesAPPLIED VEGETATION SCIENCE, Issue 1 2010S. Malaval Abstract Question: Can genetic tools combined with phytogeography help to define local plants and how geographically close the source population should be to the restoration site? Location: Subalpine and alpine French Pyrenees. Methods: The main phytogeographic boundaries in the French Pyrenees described by different authors were studied and this geographic pattern was compared with the results of genetic analysis for the four Pyrenean plants studied (Trifolium alpinum, Festuca eskia, Festuca gautieri and Rumex scutatus), based on random amplified polymorphic DNA (RAPD) marker analysis, unweighted pair-group method with arithmetic averages (UPGMA) analysis and Mantel correlograms comparing geographic and genetic distances. Results: The genetic analysis allowed definition of two main evolutionarily significant units (ESUs) for the plants under study. Although the limit between the two zones was slightly variable according to the species considered, an eastern and a western ESU was consistently observed. This delineation was concordant with the main phytogeographic boundaries of the French Pyrenees. Conclusion: RAPD markers and associated Mantel correlograms can be useful to draw ESUs for individual species when the sampling intensity is relatively dense, and similarities were revealed between species sharing the same distribution range. This delineation allowed integration of infraspecific plant variation in the management of natural resources for revegetation in the Pyrenees. Nevertheless, caution is needed for the establishment of seed pools in order to maximize genetic diversity in each of the pools during collection and production. [source] Meniscal tear in knees without surgery and the development of radiographic osteoarthritis among middle-aged and elderly persons: The multicenter osteoarthritis study,ARTHRITIS & RHEUMATISM, Issue 3 2009Martin Englund Objective Although partial meniscectomy is a risk factor for the development of knee osteoarthritis (OA), there is a lack of evidence that meniscal damage that is not treated with surgery would also lead to OA, suggesting that surgery itself may cause joint damage. Furthermore, meniscal damage is common. The aim of this study was to evaluate the association between meniscal damage in knees without surgery and the development of radiographic tibiofemoral OA. Methods We conducted a prospective case,control study nested within the observational Multicenter Osteoarthritis Study, which included a sample of men and women ages 50,79 years at high risk of knee OA who were recruited from the community. Patients who had no baseline radiographic knee OA but in whom tibiofemoral OA developed during the 30-month followup period were cases (n = 121). Control subjects (n = 294) were drawn randomly from the same source population as cases but had no knee OA after 30 months of followup. Individuals whose knees had previously undergone surgery were excluded. Meniscal damage was defined as the presence of any medial or lateral meniscal tearing, maceration, or destruction. Results Meniscal damage at baseline was more common in case knees than in control knees (54% versus 18%; P < 0.001). The model comparing any meniscal damage with no meniscal damage (adjusted for baseline age, sex, body mass index, physical activity, and mechanical knee alignment) yielded an odds ratio of 5.7 (95% confidence interval 3.4,9.4). Conclusion In knees without surgery, meniscal damage is a potent risk factor for the development of radiographic OA. These results highlight the need for better understanding, prevention, and treatment of meniscal damage. [source] The X-ray source population of the Andromeda galaxy M 31,ASTRONOMISCHE NACHRICHTEN, Issue 2 2008W. Pietsch Abstract First studies of the X-ray source population of M 31 were performed with the Einstein Observatory and ROSAT. High resolution Chandra Observatory images not only spatially resolved the center area but also supernova remnants (SNRs) in the galaxy. Source catalogues of restricted areas were presented with high astrometric accuracy. Also luminosity function studies and studies of individual sources based on Chandra and XMM-Newton observations led to a better knowledge of the X-ray source population. An XMM-Newton source catalog based on archival observations revealed more than 850 sources down to a 0.2,4.5 keV luminosity of 1035 erg s,1. EPIC hardness ratios as well as informations from earlier X-ray, optical, and radio catalogues were used to distinguish between different source classes (SNRs, supersoft sources (SSSs), X-ray binaries (XRBs), globular cluster sources within M 31, and foreground stars and objects in the background). However, many sources could only be classified as "hard". These sources may either be XRBs or Crab-like SNRs in M 31 or background sources. Two of the globular cluster sources could be identified as low mass XRBs with a neutron star as compact object as they showed type I X-ray bursts. Many of the SSSs were identified as optical novae. Inspired by these results an XMM-Newton survey of the entire D25 disk of M 31 and a dedicated program to monitor X-ray counterparts of optical novae in M 31 was started. We discuss implications for further nearby galaxy studies. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||||||||||||||||||||||||||||||||