bluuebunny/crossref_metadata_2025_split huggingface dataset:
The impact of habitat fragmentation on dispersal of Cunningham’s skink (Egernia cunninghami): evidence from allelic and genotypic analyses of microsatellites
Authors: Stow A. J. , Sunnucks P. , Briscoe D. A. , Gardner M. G. 
Published: March 2003

AbstractThe effects of habitat fragmentation on processes within and among populations are important for conservation management. Despite a broad spectrum of lifestyles and the conservation significance of many reptiles, very little work on fine‐scale population genetics has been carried out on this group. This study examines the dispersal patterns of a rock crevice‐dwelling lizard, Cunningham’s skink (Egernia cunninghami), in a naturally vegetated reserve and an adjacent deforested site. Both genotypic and genic approaches were employed, using microsatellite loci. The spatial organization of individuals with respect to pairwise relatedness coefficients and allele frequencies, along with assignment tests, were used to infer dispersal characteristics for both sexes in a natural and a cleared area. The distribution of relatedness in both habitats was spatially structured, with E. cunninghami showing high pairwise relatedness within their rocky retreat sites. Analysis of relatedness over different spatial scales, spatial autocorrelation of alleles and assignment tests, all indicated that both sexes in the cleared area show less dispersal than their counterparts in the reserve. Furthermore, deforestation may inhibit female dispersal to a greater extent than that of males. The geographical structuring of allele frequencies for adults in the cleared area, but not the reserve, indicates that habitat fragmentation has the potential to alter at least the microevolution of E. cunninghami populations.
Population structure in two sympatric species of the Lake Tanganyika cichlid tribe Eretmodini: evidence for introgression
Authors: Rüber Lukas , Meyer Axel , Sturmbauer Christian , Verheyen Erik 
Published: March 2003

AbstractPatterns of genetic differentiation were analysed and compared in two sympatric species of the endemic Lake Tanganyika cichlid tribe Eretmodini by means of mitochondrial DNA (mtDNA) sequences of the control region and six microsatellite DNA loci. The sample area covers a total of 138 km of mostly uninterrupted rocky shoreline in the Democratic Republic of Congo and includes the entire distribution range ofTanganicoduscf.irsacaethat stretches over a distance of 35 km. Both markers detected significant genetic differentiation within and between the two species.T.cf.irsacaecontained lower overall genetic variation thanEretmoduscyanostictus, possibly due to its more restricted range of distribution and its smaller effective population sizes. Complete fixation ofTanganicodusmtDNA haplotypes was observed inEretmodusat two localities, while at two other localities someTanganicodusindividuals possessedEretmodusmtDNA haplotypes. Taking into account the relatively large average sequence divergence of 6.2% between the two species, as well as the geographical distribution of mtDNA haplotypes in the lake, the observed pattern is more likely to be a consequence of asymmetric introgression than of shared ancestral polymorphism. As there is significant population differentiation between sympatricTanganicodusandEretmoduspopulations, the events of introgressions may have happened after secondary contact, but our data provide no evidence for ongoing gene flow and suggest that both species are reproductively isolated at present time.
Genetic diversity and structure of natural populations ofPlathymenia reticulata(Mimosoideae), a tropical tree from the Brazilian Cerrado
Authors: Lacerda D. R. , Acedo M. D. P. , Filho J. P. Lemos , Lovato M. B. 
Published: March 2003

AbstractPlathymenia reticulatais a tropical tree native to the Brazilian Cerrado, one of the most important and endangered ecosystems in Brazil. This species presents high‐quality wood and potential for recovery of degraded areas. Despite its importance, almost nothing is known about its genetic or ecological features. Random amplified polymorphic DNA (RAPD) markers were used to investigate the genetic diversity and structure of six natural populations ofP. reticulata. DNAs from 117 adult individuals were amplified with 10 random primers and Shannon’s index andamovawere used to evaluate the levels of genetic diversity within and among populations. Through 72 markers, 70.8% of which were polymorphic, it was possible to obtain 117 unique RAPD phenotypes. The levels of genetic variability found in the six populations ofP. reticulatawere considerable and most of the genetic variation was found between individuals within populations, although pairwise ΦSTvalues indicated significant divergence between populations. The among‐population component accounted for, respectively, 12.3% and 16% of the genetic variation, according toamovaand Shannon’s index. These results were compared with other genetic studies on plant species and such a level of differentiation among populations corresponds to that which has usually been observed for outcrossing plants. The importance of maintenance of theP. reticulatapopulations and implications of the analysis of adult individuals, considering the longevity of this species and the relatively recent Cerrado fragmentation, are discussed.
Spatial analysis of allozyme and microsatellite DNA polymorphisms in the land snailHelix aspersa(Gastropoda: Helicidae)
Authors: Arnaud J.‐F. , Madec L. , Guiller A. , Bellido A. 
Published: March 2003

AbstractThe genetic structure of the land snailHelix aspersawas investigated for 21 populations collected along a road located in the polders of the Bay of Mont‐Saint‐Michel (Brittany, France), following a sampling scheme the area of which did not exceed 900 m in length. A total of 369 individuals were genotyped for five enzymatic markers and seven microsatellite loci. We used sequential hierarchicalF‐statistics at different spatial scales and spatial autocorrelation statistics to explore recent historical patterns involved in the observed genetic distribution. Whatever the statistics used, congruent levels of spatial genetic substructuring across loci were demonstrated, excepted for one allozyme locus. Overall spatial genetic arrangement matched in a substantial fashion theoretical predictions based on the limited dispersal power of land snails. Positive autocorrelation over short‐distance classes may result from the development of genetically distinct patches of individuals organized in family‐structured colonies. Therefore, spatial signatures of averageIcorrelograms can be viewed as the expression of a stepping‐stone model of population structure, sometimes involving external migrational events. Overall, the revealed pattern of population subdivision on a microgeographical scale was suggestive of a neighbourhood structure. Finally, microsatellite loci are especially suitable for the detection of small genetic clustering, and combining different classes of markers offers the potential to gain further insight into the description of spatial genetic variability over short temporal and geographical scales.
Genetic structure and distinctness of Apis mellifera L. populations from the Canary Islands
Authors: De La Rúa P. , Galián J. , Serrano J. , Moritz R. F. A. 
Published: March 2003

AbstractThe genetic structure of Apis mellifera populations from the Canary Islands has been assessed by mitochondrial (restriction fragment length polymorphisms of the intergenic transfer RNAleu‐COII region) and nuclear (microsatellites) studies. These populations show a low level of genetic variation in terms of average number of alleles and degree of heterozygosity. Significant differences in the distribution of alleles were found in both data sets, confirming the genetic differentiation among some of the islands but not within them. Two mitochondrial haplotypes characteristic of the Canary Islands are found at high frequencies, although populations are introgressed by imported honeybees of eastern European C lineage. This introgression is rather high on Tenerife and El Hierro and low on Gran Canaria and La Gomera, whereas on La Palma it has not been recorded. The finding of microsatellite alleles characteristic of the eastern European lineage corroborates the genetic introgression. Phylogenetic analyses indicate that the Canarian honeybees are differentiated from other lineages and provide genetic evidence of their African origin.
Diversity of endophytic fungi of single Norway spruce needles and their role as pioneer decomposers
Authors: Müller Michael M. , Valjakka Rauni , Suokko Aki , Hantula Jarkko 
Published: March 2003

AbstractThe diversity of endophytic fungi within single symptomless Norway spruce needles is described and their possible role as pioneer decomposers after needle detachment is investigated. The majority (90%) of all 182 isolates from green intact needles were identified as Lophodermium piceae. Up to 34 isolates were obtained from single needles. Generally, all isolates within single needles had distinct randomly amplified microsatellite (RAMS) patterns. Single trees may thus contain a higher number of L. piceae individuals than the number of their needles. To investigate the ability of needle endophytes to act as pioneer decomposers, surface‐sterilized needles were incubated on sterile sand inoculated with autoclaved or live spruce forest humus layer. The dry weight loss of 13–17% found in needles after a 20‐week incubation did not significantly differ between the sterilized and live treatments. Hence, fungi surviving the surface sterilization of needles can act as pioneer decomposers. A considerable portion of the needles remained green during the incubation. Brown and black needles, in which the weight loss had presumably taken place, were invaded throughout by single haplotypes different from L. piceae. Instead, Tiarasporella parca, a less common needle endophyte, occurred among these invaders of brown needles. Needle endophytes of Norway spruce seem thus to have different abilities to decompose host tissues after needle cast. L. piceae is obviously not an important pioneer decomposer of Norway spruce needles. The diversity of fungal individuals drops sharply when needles start to decompose. Thus, in single needles the decomposing mycota is considerably less diverse than the endophytic mycota.
Extreme specificity in epiparasitic Monotropoideae (Ericaceae): widespread phylogenetic and geographical structure
Authors: Bidartondo M. I. , Bruns T. D. 
Published: March 2003

AbstractThe Monotropoideae (Ericaceae) are nonphotosynthetic plants that obtain fixed carbon from their fungal mycorrhizal associates. To infer the evolutionary history of this symbiosis we identified both the plant and fungal lineages involved using a molecular phylogenetic approach to screen 331 plants, representing 10 of the 12 described species. For five species no prior molecular data were available; for three species we confirmed prior studies which used limited samples; for five species all previous reports are in conflict with our results, which are supported by sequence analysis of multiple samples and are consistent with the phylogenetic patterns of host plants. The phylogenetic patterns observed indicate that: (i) each of the 13 plant phylogenetic lineages identified is specialized to a different genus or species group within five families of ectomycorrhizal Basidiomycetes; (ii) mycorrhizal specificity is correlated with phylogeny; (iii) in sympatry, there is no overlap in mature plant fungal symbionts even if the fungi and the plants are closely related; and (iv) there are geographical patterns to specificity.
Phylogeographic analysis of the threatened and endangered superconglutinate‐producing mussels of the genus Lampsilis (Bivalvia: Unionidae)
Authors: Roe Kevin J. , Hartfield Paul D. , Lydeard Charles 
Published: March 2003

AbstractSeveral species of freshwater unionid mussels in the genus Lampsilis exhibit a remarkable reproductive strategy. Female mussels of these species enclose their larvae in a minnow‐like lure, called a ‘superconglutinate’, to attract piscivorous fishes. When a fish attempts to ingest the superconglutinate the lure ruptures and the larvae are released to parasitize the fish. Of the four species of mussel which exhibit this strategy and are endemic to the Gulf Coast drainages of the southeastern United States, three are protected under the Endangered Species Act, and one is recognized as imperilled. Phylogenetic analysis of nucleotide sequences of the mitochondrial 16S ribosomal RNA and the first subunit of the cytochrome oxidase c genes was conducted on 18 individual specimens representing these four species and six outgroup taxa. Phylogenetic analyses of these data support the monophyly of the superconglutinate‐producing mussels, and indicates a strong geographical component to the data. The zoogeographic patterns of the four taxa included in the study are congruent with those seen in freshwater vertebrates, and are consistent with a vicariant pattern resulting from fluctuations in sea level during the Pleistocene. Despite the strong geographical structuring of the data, only one species, Lampsilis subangulata, was recovered as monophyletic. The authors attribute the lack of support for the monophyly of the remaining species to insufficient sequence variation and the recent origin of the ancestor of these taxa. Based on these data, any future captive breeding projects aimed at augmenting or re‐establishing populations should do so only from the appropriate source populations so as to maintain the genetic integrity of these nascent species.
A DNA test to sex ratite birds
Authors: Huynen Leon , Millar Craig D. , Lambert David M. 
Published: March 2003

AbstractDNA‐based sex tests now exist for many avian species. However, none of these tests are widely applicable to ratites. We present DNA sequence data for a locus that is W chromosome‐linked in the kiwi, ostrich, cassowary, rhea, and emu. At the amino acid level, this sequence has significant homology to X‐linked genes in platyfish and Caenorhabditis elegans. Polymerase chain reaction (PCR) primers designed to this locus allow the assignment of sex in all species of living ratites.
Cross‐species infection of blood parasites between resident and migratory songbirds in Africa
Authors: Waldenström J. , Bensch S. , Kiboi S. , Hasselquist D. , Ottosson U. 
Published: March 2003

AbstractWe studied the phylogeny of avian haemosporidian parasites,HaemoproteusandPlasmodium, in a number of African resident and European migratory songbird species sampled during spring and autumn in northern Nigeria. The phylogeny of the parasites was constructed through sequencing part of their mitochondrial cytochrome bgene. We found eight parasite lineages, fiveHaemoproteusand threePlasmodium, infecting multiple host species. Thus, 44% of the 18 haemospiridian lineages found in this study were detected in more than one host species, indicating that host sharing is a more common feature than previously thought. Furthermore, one of thePlasmodiumlineages infected species from different host families, Sylviidae and Ploceidae, expressing exceptionally large host range. We mapped transmission events, e.g. the occurrence of the parasite lineages in resident bird species in Europe or Africa, onto a phylogenetic tree. This yielded three clades, twoPlasmodiumand oneHaemoproteus, in which transmission seems to occur solely in Africa. OnePlasmodiumclade showed European transmission, whereas the remaining twoHaemoproteusclades contained mixes of lineages of African, European or unknown transmission. The mix of areas of transmission in several branches of the phylogenetic tree suggests that transmission of haemosporidian parasites to songbirds has arisen repeatedly in Africa and Europe. Blood parasites could be viewed as a cost of migration, as migratory species in several cases were infected with parasite lineages from African resident species. This cost of migration could have considerable impact on the evolution of migration and patterns of winter distribution in migrating birds.
Influences of triploidy, parentage and genetic diversity on growth of the Pacific oysterCrassostrea gigasreared in contrasting natural environments
Authors: Garnier‐Géré Pauline Hélène , Naciri‐Graven Yamama , Bougrier Serge , Magoulas Antonios , Héral Maurice , Kotoulas Georgios , Hawkins Anthony , Gérard André 
Published: March 2003

AbstractAn increasing number of hypotheses are being proposed to explain the faster growth potential of triploids in molluscs, including their partial sterility or their higher heterozygosity compared to diploids. Triploid advantage however, remains controversial for poorer sites, because of a potential trade‐off with survival. These questions were addressed inCrassostrea gigasby deploying meiosis II triploids and their diploid siblings from a single mass spawning of three males and seven females, in two contrasting locations for their trophic resources. One hundred and fifty individuals were sampled at each site after nine months, measured for weight and biochemical composition, and genotyped using three microsatellite and seven allozyme loci. Higher performance was observed at the fast‐growing site for all traits except shell weight, and triploids had greater weights and biochemical contents than diploids at harvest. Triploids also grew faster at the poorer site, and showed similar survival rates to diploids at both sites. Triploids had significantly higher average allozyme and microsatellite diversity. However, they performed better for a wide range of individual heterozygosity values, arguing for an advantage of the triploid stateper se, that could be due to positive effects on growth of both sterility of triploids with subsequent resource re‐allocation and possible faster transcription with three copies of each gene. Despite evidence of very low or no inbreeding in the diploid sample, positive associations between individual allozyme diversity and growth were detected, which explained little but significant amounts of phenotypic variation. These associations were interpreted as direct effects of allozymes, either alone or including epistatic interactions with other loci. In addition, measures of individual distance (mean‐d2) specific to microsatellites, were negatively correlated with growth in diploids, indicating possible effects of outbreeding depression between more distant genomes of parents from distinct populations.
Arbuscular mycorrhizal community composition associated with two plant species in a grassland ecosystem
Authors: Vandenkoornhuyse P. , Husband R. , Daniell T. J. , Watson I. J. , Duck J. M. , Fitter A. H. , Young J. P. W. 
Published: March 2003

AbstractArbuscular mycorrhizal (AM) fungi are biotrophic symbionts colonizing about two‐thirds of land plant species and found in all ecosystems. They are of major importance in plant nutrient supply and their diversity is suggested to be an important determinant of plant community composition. The diversity of the AM fungal community composition in the roots of two plant species (Agrostis capillaris and Trifolium repens) that co‐occurred in the same grassland ecosystem was characterized using molecular techniques. We analysed the small subunit (SSU) ribosomal RNA gene amplified from a total root DNA extract using AM fungal‐specific primers. A total of 2001 cloned fragments from 47 root samples obtained on four dates were analysed by restriction fragment length polymorphism, and 121 of them were sequenced. The diversity found was high: a total of 24 different phylotypes (groups of phylogenetically related sequences) colonized the roots of the two host species. Phylogenetic analyses demonstrate that 19 of these phylotypes belonged to the Glomaceae, three to the Acaulosporaceae and two to the Gigasporaceae. Our study reveals clearly that the AM fungal community colonizing T. repens differed from that colonizing A. capillaris, providing evidence for AM fungal host preference. In addition, our results reveal dynamic changes in the AM fungal community through time.
Fitness of backcross six of hybrids between transgenic oilseed rape (Brassica napus) and wild radish (Raphanus raphanistrum)
Authors: Gueritaine G. , Sester M. , Eber F. , Chevre A. M. , Darmency H. 
Published: March 2003

AbstractThe process of introgression between a transgenic crop modified for better agronomic characters and a wild relative could lead potentially to increased weediness and adaptation to the environment of the wild species. However, the formation of hybrid and hybrid progeny could be associated with functional imbalance and low fitness, which reduces the risk of gene escape and establishment of the wild species in the field. Our work compares the fitness components of parents and different types of backcross in the sixth generation of hybrids between transgenic oilseed rape (Brassica napus, AACC, 2n = 38) resistant to the herbicide glufosinate and wild radish (Raphanus raphanistrum, RrRr, 2n = 18). The backcross with oilseed rape cytoplasm (OBC) has a fitness value 100 times lower than that of the backcross with wild radish cytoplasm (RBC). The herbicide‐resistant RBC has similar growth to the susceptible RBC, but final male and female fitness values are two times lower. In turn, susceptible RBC exhibit similar fitness to the control wild radishes. The relative fitnesses of the different types are the same whether or not they grow under competitive conditions. The consequence on fitness of the chromosome location of the transgene conferring resistance and the relevance of these results to the impact of gene flow on the environment are discussed.
Separating historic events from recurrent processes in cryptic species: phylogeography of mud snails (Hydrobia spp.)
Authors: Wilke T. , Pfenninger M. 
Published: March 2003

AbstractThe present study combines methods that were designed to infer intraspecific relationships (e.g. nested‐clade analysis (NCA), mismatch distributions and maximum likelihood gene flow analysis) to analyse historic events and recurrent processes in the cryptic mud snail species Hydrobia acuta and H. glyca. Specifically, we test the proposed allopatry of cryptic species and whether the peculiar range‐subdivision of the putative subspecies H. a. acuta and H. a. neglecta is a result of long‐distance dispersal or continuous range expansion. The NCA indicates a past fragmentation of the two H. acuta subspecies as well as past fragmentations within H. glyca. Gene‐flow analyses show extensive gene flow in an E–W direction (towards the Atlantic) in the Mediterranean H. a. acuta, generally low gene flow in a W–E direction in the Atlantic H. a. neglecta and complex gene‐flow pattern in a N–S but also in a S–N direction (against the Gulf Stream) in H. glyca. Based on these data and supportive ecological and oceanographical data, we hypothesize that the separation of the two H. acuta subspecies was not caused by long‐distance dispersal but by a range shift and/or range expansion of the closely related competitor H. glyca as a result of an interglacial warming with a subsequent range shift in H. acuta. Moreover, our data do not show evidence for a long‐term, stable sympatry of Hydrobia species, supporting the concept of allopatric relationships within cryptic radiations. NCA and gene‐flow analyses indicate that the only sympatric population found in our study is the result of a recent dispersal event from the nearby Mediterranean. It is assumed that allopatric relationships in ephemeral Hydrobia populations constitute an evolutionary advantage relative to competition, recruitment and re‐establishment of habitats. Mechanisms that could be of relevance for maintaining allopatry are discussed.