bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wolbachia infection complexity among insects in the tropical rice‐field community
Authors: Kittayapong P. , Jamnongluk W. , Thipaksorn A. , Milne J. R. , Sindhusake C. 
Published: December 2004

Abstract Wolbachia are a group of intracellular bacteria that cause reproductive alterations in their arthropod hosts. Widely discordant host and Wolbachia phylogenies indicate that horizontal transmission of these bacteria among species sometimes occurs. A likely means of horizontal transfer is through the feeding relations of organisms within communities. Feeding interactions among insects within the rice‐field insect community have been well documented in the past. Here, we present the results of a polymerase chain reaction‐based survey and phylogenetic analysis of Wolbachia strains in the rice‐field insect community of Thailand. Our field survey indicated that 49 of 209 (23.4%) rice‐field insect species were infected with Wolbachia. Of the 49 infected species, 27 were members of two feeding complexes: (i) a group of 13 hoppers preyed on by 2 mirid species and parasitized by a fly species, and (ii) 2 lepidopteran pests parasitized by 9 wasp species. Wolbachia strains found in three hoppers, Recilia dorsalis, Nephotettix malayanus and Nisia nervosa, the two mirid predators, Cyrtorhinus lividipennis and Tytthus chinensis, and the fly parasitoid, Tomosvaryella subvirescens, were all in the same Wolbachia clade. In the second complex, the two lepidopteran pests, Cnaphalocrocis medinalis and Scirpophaga incertulas, were both infected with Wolbachia from the same clade, as was the parasitoid Tropobracon schoenobii. However, none of the other infected parasitoid species in this feeding complex was infected by Wolbachia from this clade. Mean (± SD) genetic distance of Wolbachia wsp sequences among interacting species pairs of the hopper feeding complex (0.118 ± 0.091 nucleotide sequence differences), but not for the other two complexes, was significantly smaller than that between noninteracting species pairs (0.162 ± 0.079 nucleotide sequence differences). Our results suggest that some feeding complexes, such as the hopper complex described here, could be an important means by which Wolbachia spreads among species within arthropod communities.
Phylogeography of the common vole (Microtus arvalis) with particular emphasis on the colonization of the Orkney archipelago
Authors: Haynes Susan , Jaarola Maarit , Searle Jeremy B. 
Published: December 2004

AbstractTo investigate the human introduction of the common vole Microtus arvalis onto the Orkney islands, the complete cytochrome b gene was sequenced in 41 specimens from both Orkney (four localities) and elsewhere in their range (26 localities). Orkney voles belonged to the same phylogenetic lineage, ‘Western’, as individuals from France and Spain indicating southwestern Europe as the most likely source area for the islands. This result is of interest with respect to the movement and trading links of the Neolithic people who likely transported the voles. As well as the Western lineage, our phylogenetic trees revealed three other purely European lineages: the ‘Italian’ (single specimen from N. Italy), the ‘Central’ (Germany, Netherlands, Denmark) and the ‘Eastern’ (Hungary, Slovakia, Poland, Ukraine, Finland, European Russia). Individuals from European Russia, W. Siberia, Georgia, Ukraine and Armenia formed a fifth distinct lineage coinciding with the distribution of the ‘obscurus’ chromosomal form of M. arvalis. These phylogeographical data suggest that M. arvalis occupied multiple refugia during the last glaciation.
Holarctic phylogeography of the root vole (Microtus oeconomus): implications for late Quaternary biogeography of high latitudes
Authors: Brunhoff C. , Galbreath K. E. , Fedorov V. B. , Cook J. A. , Jaarola M. 
Published: December 2004

AbstractA species‐wide phylogeographical study of the root vole (Microtus oeconomus) was performed using the whole 1140 base pair mitochondrial (mt) cytochromebgene. We examined 83 specimens from 52 localities resulting in 65 unique haplotypes. Our results demonstrate that the root vole is divided into four main mtDNA phylogenetic lineages that seem to have largely allopatric distributions. Net divergence estimates (2.0–3.5%) between phylogroups, as well as relatively high nucleotide diversity estimates within phylogroups, indicate that the distinct phylogeographical structure was initiated by historical events that predated the latest glaciation. European root voles are divided into a Northern and a Central mtDNA phylogroup. The mtDNA data in concert with fossil records imply that root voles remained north of the classical refugial areas in southern Europe during the last glacial period. The currently fragmented populations in central Europe belong to a single mtDNA phylogroup. The Central Asian and the North European lineages are separated by the Ural Mountains, a phylogeographical split also found in collared lemmings (Dicrostonyx) and the common vole (M. arvalis). The Beringian lineage occurs from eastern Russia through Alaska to northwestern Canada. This distribution is congruent with the traditional boundaries of the Beringian refugium and with phylogeographical work on other organisms. In conclusion, similarities between the phylogeographical patterns in the root vole and other rodents, such as Arctic and subarctic lemmings, as well as more temperate vole species, indicate that late Quaternary geological and climatic events played a strong role in structuring northern biotic communities.
Phylogeography of Ponto‐Caspian crustaceans: a benthic–planktonic comparison
Authors: Cristescu Melania E. A. , Hebert Paul D. N. , Onciu Teodora M. 
Published: December 2004

AbstractThe Black, Azov, Caspian and Aral Seas, remnants of the intracontinental Paratethys basin, are home to a spectacular diversity of crustaceans. This study examines the past history of the Ponto‐Caspian fauna through comparative phylogeographical studies on both benthic and planktonic taxa, based on an examination of nucleotide diversity in the mitochondrial, cytochrome c oxidase subunit 1 (COI) gene. The COI data reveal a striking example of phylogeographical concordance. All species analysed, three amphipods and three cladocerans, are characterized by two monophyletic clades corresponding to the Black and Caspian regions. However, this phylogeographical partition is, on average, four times deeper for the benthic amphipods than for the planktonic cladocerans. Based on standard molecular clocks, the Black and Caspian lineages of benthic crustaceans diverged at varied intervals from 1 to 8 million years ago. By contrast, planktonic lineages are more recent with their divergence occurring in the last million years. Levels of intraspecific polymorphisms are variable and generally lower in planktonic than benthic taxa. The mechanisms responsible for the high diversity of crustaceans in the Ponto‐Caspian region are discussed on the basis of these results.
Molecular evolution and quantitative variation for chemosensory behaviour in the nematode genus Caenorhabditis
Authors: Jovelin R. , Ajie B. C. , Phillips P. C. 
Published: December 2004

Abstract Caenorhabditis elegans is a model organism in biology, yet despite the tremendous information generated from genetic, genomic and functional analyses, C. elegans has rarely been used to address questions in ecological genetics. Here, we analyse genetic variation for chemosensory behaviour, an ecologically important trait that is also genetically well characterized, at both the phenotypic and molecular levels within three species of the genus Caenorhabditis. We show that the G‐protein ODR‐3 plays an important role in chemosensory avoidance behaviour and identify orthologues of odr‐3 in C. briggsae and C. remanei. Both quantitative genetic analysis of chemosensory behaviour and molecular population genetic analysis of odr‐3 show that there is little genetic variation among a worldwide collection of isolates of the primarily selfing C. elegans, whereas there is substantially more variation within a single population of the outcrossing C. remanei. Although there are a large number of substitutions at silent sites within odr‐3 among the three species, molecular evolution at the protein level is extremely conserved, suggesting that odr‐3 plays an important role in cell signalling during chemosensation and/or neuronal cilia development in C. remanei and in C. briggsae as it does in C. elegans. Our results suggest that C. remanei may be a more suitable subject for ecological and evolutionary genetic studies than C. elegans.
Candidate gene analysis of metamorphic timing in ambystomatid salamanders
Authors: Voss S. R. , Prudic K. L. , Oliver J. C. , Shaffer H. B. 
Published: December 2004

AbstractAlthough much is known about the ecological significance of metamorphosis and metamorphic timing, few studies have examined the underlying genetic architecture of these traits, and no study has attempted to associate phenotypic variation to molecular variation in specific genes. Here we report on a candidate gene approach (CGA) to test specific loci for a statistical contribution to variation in metamorphic timing. Three segregating populations (SP1, SP2 and SP3) were constructed utilizing three species of paedomorphic Mexican ambystomatid salamander, including the axolotl,Ambystoma mexicanum. We used these replicated species to test the hypothesis that inheritance of alternate genotypes at two thyroid hormone receptor loci (TRα, TRβ) affects metamorphic timing in ambystomatid salamanders. A significantTRα*SP effect indicated that variation in metamorphic timing may be influenced byTRαgenotype, however, the effect was not a simple one, as both the magnitude and direction of the phenotypic effect depended upon the genetic background. These are the first data to implicate a specific gene in contributing to variation in metamorphic timing. In general, candidate gene approaches can be extended to any number of loci and to any organism where simple genetic crosses can be performed to create segregating populations. The approach is thus of particular value in ecological studies where target genes have been identified but the study organism is not one of the few well‐characterized model systems that dominate genetic research.
A ‘fair go’* for coral hybridization
Authors: Miller David J. , Van Oppen Madeleine J. H. 
Published: December 2004

AbstractHybridisation between coral species clearly occurs in vitro, but the evolutionary significance of this cross‐fertility is still the subject of much debate. Compelling genetic and reproductive evidence support introgressive hybridization amongst Indo‐Pacific members of the scleractinian genus Acropora. Although population genetic analyses indicate that interspecific hybridization events are relatively rare, they are likely be important on evolutionary time scales, creating the capacity for adaptive evolution by increasing genomic diversity and heterozygosity. However, in a recent paper based exclusively on the three endemic Caribbean Acropora species, Vollmer and Palumbi (2002) dispute the occurrence of reticulation in corals. Here we use data from both the Vollmer and Palumbi study and our earlier paper on the same species (van Oppen et al., 2000) to show that reticulation has occurred amongst the Caribbean Acropora species. Furthermore, conclusions based on the limited Caribbean Acropora fauna cannot simply be extrapolated to Indo‐Pacific corals, and it is inappropriate to view some coral species as ‘immortal mules’.
Patterns of nucleotide variation in homoeologous regulatory genes in the allotetraploid Hawaiian silversword alliance (Asteraceae)
Authors: Lawton‐Rauh Amy , Robichaux Robert H. , Purugganan Michael D. 
Published: December 2004

AbstractGenome‐wide duplication (polyploidization) is prevalent in a large number of eukaryotic organisms and is particularly widespread in flowering plants. Polyploid species appear to vary from their diploid progenitors in a variety of ecologically important traits, suggesting that genome duplications provide a mechanism for ecological diversification. Studies of nucleotide variation at duplicate genes that arise via polyploidization allow us to infer the evolutionary forces that act on these polyploid loci. In an effort to examine the evolutionary dynamics of homoeologous loci, molecular population genetic analyses were undertaken for duplicate regulatory genes in the allopolyploid Hawaiian silversword alliance, a premier example of adaptive radiation. The levels and patterns of nucleotide variation for the floral homeotic genes ASAPETALA1 (ASAP1) and ASAPETALA3/TM6 (ASAP3/TM6) were studied in two species representing different lineages within the Hawaiian silversword alliance: Argyroxiphium sandwicense ssp. macrocephalum and Dubautia ciliolata ssp. glutinosa. Homoeologueous copies of ASAP1 and ASAP3/TM6 show differing levels and patterns of nucleotide polymorphism. Duplicate ASAP1 copies have similar levels of nucleotide diversity and haplotype structure in both species; by contrast, duplicate ASAP3/TM6 genes display different levels and patterns of variation in D. ciliolata ssp. glutinosa. Additionally, D. ciliolata ssp. glutinosa appears to be segregating for a moderate frequency null allele in one ASAP3/TM6 homoeologue. These results suggest that differing evolutionary forces can affect duplicate loci arising from allopolyploidization.
Patterns of DNA sequence diversity and genetic structure after a range expansion: lessons from the infinite‐island model
Authors: Excoffier Laurent 
Published: December 2004

AbstractIt has been long recognized that population demographic expansions lead to distinctive features in the molecular diversity of populations. However, recent simulation results have suggested that a distinction could be made between a pure demographic expansion in an unsubdivided population, and a range expansion in a subdivided population, both leading to a large increase in the total number of the individuals. In order to better characterize the effect of a range expansion, I introduce a simple model of instantaneous expansion under an infinite‐island model, under which I derive the distribution of the number of mutation differences between pairs of genes (the mismatch distribution), the heterozygosity, the average number of pairwise difference, and the fixation index FST. These derivations are checked against simulations, and are shown to lead to results qualitatively similar to those one would obtain after a range expansion in a 2‐dimensional stepping‐stone model. I then apply these results to estimate immigration rates in hunter‐gather and post‐Neolithic human populations from patterns of mitochondrial (mtDNA) diversity. Potential problems with this estimation procedure are also discussed.
Combining demographic, environmental and genetic data to test hypotheses about colonization events in metapopulations
Authors: Gaggiotti O. E. , Brooks S. P. , Amos W. , Harwood J. 
Published: December 2004

AbstractWe describe a method for making inferences about the factors that influence colonization processes in natural populations. We consider the general situation where we have genetic data from a newly colonized population and also fromIsource populations that may have contributed individuals to the founding group that established the new population. The model assumes thatp(biotic/abiotic) factors,G1, … ,Gpmay have influenced some individuals in some of the source populations to find a new habitat patch where they could establish a new population. The aim of the method is to determine the composition of the founding group and to ascertain if the aforementioned factors have indeed played a role in the colonization event. We investigate the performance of our method using simulated data sets and illustrate its application with data from the grey sealHalichoerus grypus. These applications demonstrate that the method can identify accurately those factors that are most important for the founding of new populations. This is the case even when genetic differentiation among source populations is low. The estimates of the contribution that each source population makes to the founding groups is somewhat sensitive to the degree of genetic differentiation but it is still possible to identify the sources that are the main contributors to the founding group, even when genetic differentiation is low (FST = 0.01).
Using nuclear haplotypes with microsatellites to study gene flow between recently separated Cichlid species
Authors: Hey Jody , Won Yong‐Jin , Sivasundar Arjun , Nielsen Rasmus , Markert Jeffrey A. 
Published: December 2004

AbstractWhen populations or species have recently separated they often share genetic variation. However, it can be difficult to determine whether shared polymorphisms are the result of gene flow, the result of the persistence of variation in both populations since the time of common ancestry, or both of these factors. We have developed an empirical protocol for using loci that include unique nuclear DNA sequence haplotypes together with linked microsatellites or short tandem repeats (STRs). These ‘HapSTRs’ offer the potentially high resolution associated with the high mutation rate of STRs, together with the advantages of low homoplasy of unique sequence DNA. We also describe a new procedure for estimating the likelihood of HapSTR data under an Isolation with Migration model. An example using Cichlid fishes from Lake Malawi is described. The analysis suggests that the species have been exchanging genes since the time they began to diverge.
Evidence of genetic distinction and long‐term population decline in wolves (Canis lupus) in the Italian Apennines
Authors: Lucchini V. , Galov A. , Randi E. 
Published: December 2004

AbstractHistorical information suggests the occurrence of an extensive human‐caused contraction in the distribution range of wolves (Canis lupus) during the last few centuries in Europe. Wolves disappeared from the Alps in the 1920s, and thereafter continued to decline in peninsular Italy until the 1970s, when approximately 100 individuals survived, isolated in the central Apennines. In this study we performed a coalescent analysis of multilocus DNA markers to infer patterns and timing of historical population changes in wolves surviving in the Apennines. This population showed a unique mitochondrial DNA control‐region haplotype, the absence of private alleles and lower heterozygosity at microsatellite loci, as compared to other wolf populations. Multivariate, clustering and Bayesian assignment procedures consistently assigned all the wolf genotypes sampled in Italy to a single group, supporting their genetic distinction. Bottleneck tests showed evidences of population decline in the Italian wolves, but not in other populations. Results of a Bayesian coalescent model indicate that wolves in Italy underwent a 100‐ to 1000‐fold population contraction over the past 2000–10 000 years. The population decline was stronger and longer in peninsular Italy than elsewhere in Europe, suggesting that wolves have apparently been genetically isolated for thousands of generations south of the Alps. Ice caps covering the Alps at the Last Glacial Maximum (c. 18 000 years before present), and the wide expansion of the Po River, which cut the alluvial plains throughout the Holocene, might have provided effective geographical barriers to wolf dispersal. More recently, the admixture of Alpine and Apennine wolf populations could have been prevented by deforestation, which was already widespread in the fifteenth century in northern Italy. This study suggests that, despite the high potential rates of dispersal and gene flow, local wolf populations may not have mixed for long periods of time.
Multitrophic interactions involving genetically modified potatoes, nontarget aphids, natural enemies and hyperparasitoids
Authors: Cowgill S. E. , Danks C. , Atkinson H. J. 
Published: December 2004

AbstractGenetically modified (GM) potatoes expressing a cysteine proteinase inhibitor (cystatin) have been developed as an option for the management of plant parasitic nematodes. The relative impact of such plants on predators and parasitoids (natural enemies) of nontarget insects was determined in a field trial. The trial consisted of GM plants, control plants grown in soil treated with a nematicide and untreated control plants. The quantity of nontarget aphids and their quality as hosts for natural enemies were studied. Aphid density was significantly reduced by nematicide treatment and few natural enemies were recorded from treated potatoes during the study. In contrast, similar numbers of aphids and their more adundant predators were recorded from the untreated control and the GM potatoes. The size of aphids on GM and control plants was recorded twice during the study. During the first sampling period (2–9 July) aphids clip‐caged on GM plants were smaller than those on control plants. During the second sampling period (23–30 July) there was no difference in aphid size between those from the GM and control plants. Host size is an important component of host quality. It can affect the size and fecundity of parasitoid females and the sex ratio of their offspring. However, neither the fitness of females of Aphidius ervi, the most prevalent primary parasitoid, nor the sex ratio of their progeny, were affected when the parasitoids developed on aphids feeding on GM plants. Two guilds of secondary parasitoid were also recorded during the study. The fitness of the most abundant species, Aspahes vulgaris, was not affected when it developed on hosts from GM plants. The transgene product, OC IΔD86, was not detected in aphids that had fed on GM plants in the field, suggesting that there is minimal secondary exposure of natural enemies to the inhibitor. The results indicate that transgenic nematode resistance is potentially more compatible with aphid biological control than is current nematicide use.
Tandem constructs to mitigate transgene persistence: tobacco as a model
Authors: Al‐Ahmad Hani , Galili Shmuel , Gressel Jonathan 
Published: December 2004

AbstractSome transgenic crops can introgress genes into other varieties of the crop, to related weeds or themselves remain as ‘volunteer’ weeds, potentially enhancing the invasiveness or weediness of the resulting offspring. The presently suggested mechanisms for transgene containment allow low frequency of gene release (leakage), requiring the mitigation of continued spread. Transgenic mitigation (TM), where a desired primary gene is tandemly coupled with mitigating genes that are positive or neutral to the crop but deleterious to hybrids and their progeny, was tested as a mechanism to mitigate transgene introgression. Dwarfism, which typically increases crop yield while decreasing the ability to compete, was used as a mitigator. A construct of a dominant ahasR (acetohydroxy acid synthase) gene conferring herbicide resistance in tandem with the semidominant mitigator dwarfing Δgai (gibberellic acid‐insensitive) gene was transformed into tobacco (Nicotiana tabacum). The integration and the phenotypic stability of the tandemly linked ahasR and Δgai genomic inserts in later generations were confirmed by polymerase chain reaction. The hemizygous semidwarf imazapyr‐resistant TM T1 (= BC1) transgenic plants were weak competitors when cocultivated with wild type segregants under greenhouse conditions and without using the herbicide. The competition was most intense at close spacings typical of weed offspring. Most dwarf plants interspersed with wild type died at 1‐cm, > 70% at 2.5‐cm and 45% at 5‐cm spacing, and the dwarf survivors formed no flowers. At 10‐cm spacing, where few TM plants died, only those TM plants growing at the periphery of the large cultivation containers formed flowers, after the wild type plants terminated growth. The highest reproductive TM fitness relative to the wild type was 17%. The results demonstrate the suppression of crop–weed hybrids when competing with wild type weeds, or such crops as volunteer weeds, in seasons when the selector (herbicide) is not used. The linked unfitness would be continuously manifested in future generations, keeping the transgene at a low frequency.