Search results for "effective population size"
showing 10 items of 35 documents
Genetic polymorphism and high detrimental load in natural populations of Drosophila melanogaster from cellar and vineyard
1987
Two Spanish natural populations of Drosophila melanogaster have been analysed with respect to genetic variability in third chromosome viability. The two populations, although from the same locality, belong to relatively different habitats: the inside of a cellar and a vineyard. The patterns of homozygote and heterozygote viability are similar in both populations. The homozygous detrimental loads estimated are very high and the values for the D:L (detrimental/lethal) ratio close to 2.5, which is higher than any previously found. The environmental variance of viability, average degrees of dominance of lethal genes and of viability polygenes and effective population sizes were estimated in eac…
r- and K-selection in experimental populations of vesicular stomatitis virus.
2002
Here we explore the adaptation of vesicular stomatitis RNA virus to different population densities and the existence of a trade-off between r- and K-selection. Increasing population density represents a challenging special situation for viruses, since different selective pressures arise depending upon the number of available host cells per virus. Adaptation to low density represents a prototypical case of r-selection, where the optimal evolutionary solution should be a high replication rate. Adaptation to high density represents a case of K-selection. In this case, genotypes optimally exploiting the resources, instead of faster replicating ones, should be selected. Five independent populati…
Low effective population sizes and limited connectivity inxerothermic beetles: implications for the conservation ofan endangered habita
2014
Fragmentation and isolation may have detrimental effects on the viability of populations. Xerothermic grasslands, which are extra-zonal analogues of steppes, are among Europe's most endangered natural environments. Information about connectivity between the remaining habitat patches is critical for effective conservation planning. However, very little is known about the actual levels of isolation of individual xerothermic patches at the inter-regional and local scale. In this study, 16 microsatellite loci were used to investigate genetic diversity, structuring, effective sizes (Ne), and connectivity among populations of the weevil Centricnemus leucogrammus at various geographic scales. Anal…
The genetic structure of Norway
2020
AbstractThe aim of the present study was to describe the genetic structure of the Norwegian population using genotypes from 6369 unrelated individuals with detailed information about places of residence. Using standard single marker- and haplotype-based approaches, we report evidence of two regions with distinctive patterns of genetic variation, one in the far northeast, and another in the south of Norway, as indicated by fixation indices, haplotype sharing, homozygosity, and effective population size. We detect and quantify a component of Uralic Sami ancestry that is enriched in the North. On a finer scale, we find that rates of migration have been affected by topography like mountain ridg…
Patterns and causes of incongruence between plastid and nuclear Senecioneae (Asteraceae) phylogenies
2010
One of the longstanding questions in phylogenetic systematics is how to address incongruence among phylogenies obtained from multiple markers and how to determine the causes. This study presents a detailed analysis of incongruent patterns between plastid and ITS/ETS phylogenies of Tribe Senecioneae (Asteraceae). This approach revealed widespread and strongly supported incongruence, which complicates conclusions about evolutionary relationships at all taxonomic levels. The patterns of incongruence that were resolved suggest that incomplete lineage sorting (ILS) and/or ancient hybridization are the most likely explanations. These phenomena are, however, extremely difficult to distinguish beca…
Genética de la conservación: la aplicación de los conceptos de la evolución a la conservación de la diversidad biológica
2013
La comprensión de las fuerzas de cambio evolutivo que actúan sobre las poblaciones, en conjunción con las técnicas más modernas de análisis genético, lleva aplicándose en los últimos veinte años al servicio de la conservación de la biodiversidad. Esta nueva aplicación de la genética ha recibido el nombre de genética de la conservación.
Demographic characterization and genetic variability of the Girgentana goat breed by the analysis of genealogical data
2004
The aim of this paper is to present an overview of the actual Sicilian Girgentana population structure by the analysis ofgenealogical data. Statistics show that in 1983 the population consisted of 30,000 Girgentana goats; ten years lateralmost 98% of the entire Girgentana population disappeared. The remaining population consists of 461 individuals (134males and 327 females), with 368 living animals. The effective population size is 380 individuals. The inbreeding rate pergeneration was equal to 0.13%. The average estimated inbreeding level within the living male population was equal to0.8% (0-15%); and the average inbreeding level within the living female population was equal to 0.7% (0-31%…
Biogeography of the smooth snake (Coronella austriaca): origin and conservation of the northernmost population
2014
Understanding historical range expansions and population demography can be crucial for the conservation and management of endangered species. In doing so, valuable information can be obtained regarding, for example, the identification of isolated populations, associations to particular habitats and distribution range shifts. As poikilotherms, snakes are vulnerable to environmental changes that can greatly shape their distribution ranges. Here we used mitochondrial data to elucidate the origin of the smooth snake population in Aland island, which is the northernmost location where the species is found. In Aland, we used mitochondrial and microsatellite data to fine-map its spatial genetic st…
Continental-scale patterns of pathogen prevalence: a case study on the corncrake
2014
Pathogen infections can represent a substantial threat to wild populations, especially those already limited in size. To determine how much variation in the pathogens observed among fragmented populations is caused by ecological factors, one needs to examine systems where host genetic diversity is consistent among the populations, thus controlling for any potentially confounding genetic effects. Here, we report geographic variation in haemosporidian infection among European populations of corncrake. This species now occurs in fragmented populations, but there is little genetic structure and equally high levels of genetic diversity among these populations. We observed a longitudinal gradient…
REPLICATED ORIGIN OF FEMALE-BIASED ADULT SEX RATIO IN INTRODUCED POPULATIONS OF THE TRINIDADIAN GUPPY (POECILIA RETICULATA)
2014
There are many theoretical and empirical studies explaining variation in offspring sex ratio but relatively few that explain variation in adult sex ratio. Adult sex ratios are important because biased sex ratios can be a driver of sexual selection and will reduce effective population size, affecting population persistence and shapes how populations respond to natural selection. Previous work on guppies (Poecilia reticulata) gives mixed results, usually showing a female-biased adult sex ratio. However, a detailed analysis showed that this bias varied dramatically throughout a year and with no consistent sex bias. We used a mark-recapture approach to examine the origin and consistency of fema…