			Home About us Contact

High Genotypic Diversity (high + genotypic_diversity)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Grain aphid population structure: no effect of fungal infections in a 2-year field study in Denmark

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2008
A. B. Jensen
Abstract 1,Sitobion avenae (F.) is a serious pest in Danish cereal crops. To understand the population genetic structure, aphids were sampled in seven different winter wheat (Triticum sativum Lamarck) fields throughout Denmark. The aphids were genotyped with seven microsatellite markers. In total, 2075 aphids were collected and 1203 of these were genotyped. 2,The Danish S. avenae populations displayed very high genotypic diversity, high percentages of unique genotypes and low linkage disequilibria; this is likely to be a result of genetic recombination encompassed by their holocyclic lifestyle. The populations showed very limited differentiation and no sign of isolation by distance. Almost all the genetic variation was ascribed within the populations rather than between populations, probably due to a high migration rate at approximate 10% per generation. 3,Seasonal changes in clonal diversity and distribution of asexual summer generations of S. avenae within the infestation period in a single winter wheat field were followed over two consecutive years by weekly sampling from 60 plots each of 20 × 20 m. Clonal diversity was high in all samples with no dominant clonal lineages and no significant difference in the genotypic diversity between weeks or between years. However, a temporal genetic differentiation effect, throughout the infestation, suggests that selective factors or high temporal migration play an important role in shaping the genetic structure S. avenae. 4,Analyses of fungal infected and uninfected aphids were performed to test whether some clonal linage were more often infected by fungi from the Entomophthorales under field conditions. In total, 54 progeny from aphids with Entomophthorales were genotyped and compared with 422 uninfected aphid genotypes. The Entomophthorales-infected aphid genotypes did not cluster out together, suggesting that these fungal pathogens did not affect the population differentiation or clonal distribution of S. avenae in a Danish agroecosystem. 5,Our findings indicate that S. avenae populations can be controlled using conservation biological control [source]

Biodiversity in microbial communities: system scale patterns and mechanisms

MOLECULAR ECOLOGY, Issue 7 2009
J. JACOB PARNELL
Abstract The relationship between anthropogenic impact and the maintenance of biodiversity is a fundamental question in ecology. The emphasis on the organizational level of biodiversity responsible for ecosystem processes is shifting from a species-centred focus to include genotypic diversity. The relationship between biodiversity measures at these two scales remains largely unknown. By stratifying anthropogenic effects between scales of biodiversity of bacterial communities, we show a statistically significant difference in diversity based on taxonomic scale. Communities with intermediate species richness show high genotypic diversity while speciose and species-poor communities do not. We propose that in species-poor communities, generally comprising stable yet harsh conditions, physiological tolerance and competitive trade-offs limit both the number of species that occur and the loss of genotypes due to decreases in already constrained fitness. In species-rich communities, natural environmental conditions result in well-defined community structure and resource partitioning. Disturbance of these communities disrupts niche space, resulting in lower genotypic diversity despite the maintenance of species diversity. Our work provides a model to inform future research about relationships between species and genotypic biodiversity based on determining the biodiversity consequences of changing environmental context. [source]

Three-dimensional fine-scale genetic structure of the neotropical epiphytic orchid, Laelia rubescens

MOLECULAR ECOLOGY, Issue 5 2004
Dorset W. Trapnell
Abstract Epiphytic plants occupy three-dimensional space, which allows more individuals to be closely clustered spatially than is possible for populations occupying two dimensions. The unique characteristics of epiphytes can act in concert to influence the fine-scale genetic structure of their populations which can, in turn, influence mating patterns and other population phenomena. Three large populations of Laelia rubescens (Orchidaceae) in the Costa Rican seasonal dry forest were sampled at two levels of intensity to determine: (i) whether individual clusters contain more than one genotype, and (ii) the spatial distribution and fine-scale genetic structure of genotypes within populations. Samples were assayed for their multilocus allozyme genotypes and spatial autocorrelation analyses were performed. High levels of genetic diversity, high genotypic diversity and low among-population variation were found. In the larger clusters, multiple genets per cluster were common with discrete clusters containing up to nine genotypes. Spatial autocorrelation analyses indicated significant positive genetic structure at distances of , 45 cm. This result is likely due to the formation of discrete clusters by vegetative reproduction, as well as the establishment of sexually derived progeny within and near maternal clusters. [source]

Genetic structure of Mycosphaerella graminicola populations in Iran

PLANT PATHOLOGY, Issue 5 2010
M. Abrinbana
To provide insight into the genetic structure of Mycosphaerella graminicola populations in Iran, a total of 221 isolates were collected from naturally infected wheat fields of five major wheat-growing provinces and analysed using AFLP markers and mating-type loci. All populations showed intermediate to high genotypic diversity. In the Golestan and Ardabil populations two mating types were found at near-equal frequencies, whilst all populations were in gametic disequilibrium. Moreover, clonal haplotypes were identified in different sampling sites within a field in both the Khuzestan and Fars provinces, demonstrating that pycnidia are probably the primary source of inoculum. All five populations had low levels of gene diversity and had private bands. Low levels of gene flow and high genetic differentiation were observed among populations and different clustering methods revealed five genetically distinct groups in accordance with the sampling areas. The Golestan and East Azarbaijan populations were more genetically differentiated than the others. Random genetic drift, selection and geographic barriers may account for the differentiation of the populations. The results of this study indicate a population structure of M. graminicola in Iran contrasting to that of most other countries studied. [source]