Search results for "POPULATION"

Biogeography and temporal progression during the evolution of striped dolphin population structure in European waters

2017

Aim: We investigated the population genetic structure of a highly mobile marine species, the striped dolphin, Stenella coeruleoalba (Meyen, 1833), along a geographical range with habitat transitions and historical dynamics to identify the causes of genetic divergence, and to assess the effect of past climate change on demography and population connectivity. Location: North-east Atlantic Ocean and Mediterranean Sea. Methods: Twenty microsatellite loci were used in conjunction with coalescent methods to investigate the genetic structure and demographic history of striped dolphins (Stenella coeruleoalba) in the Mediterranean Sea and eastern North Atlantic Ocean. Approximate Bayesian modelling …

Frequency-Dependent Selection in a Mammalian RNA Virus

1997

RNA viruses have been used as experimental systems to test evolutionary hypotheses such as Muller's ratchet (Chao 1990; Duarte et al. 1992, 1993; Clarke et al. 1993), the Red Queen hypothesis (Clarke et al. 1994), the nature of the adaptive topography (Elena, 1995; Elena et al. 1996), and the dynamics of adaptive evolution (Elena 1995; Novella et al. 1995). Two hypotheses which have received attention in virus studies are the competitive exclusion principle and frequency-dependent selection. The competitive exclusion principle (Hardin 1960) states that two populations or species competing for the same limiting resource cannot stably coexist because one competitor will displace the other. An…

2018

One of the most relevant characteristics of the extant Southern Ocean fauna is its resiliency to survive glacial processes of the Quaternary. These climatic events produced catastrophic habitat reductions and forced some marine benthic species to move, adapt or go extinct. The marine benthic species inhabiting the Antarctic upper continental shelf faced the Quaternary glaciations with different strategies that drastically modified population sizes and thus affected the amount and distribution of intraspecific genetic variation. Here we present new genetic information for the most conspicuous regular sea urchin of the Antarctic continental shelf, Sterechinus neumayeri. We studied the pattern…

Molecular phylogeography ofThymus herba-barona(Lamiaceae): Insight into the evolutionary history of the flora of the western Mediterranean islands

2011

Thymus herba-barona is endemic to Majorca, Corsica, and Sardinia. In order to gain insight into its evolutionary history, we examined the genetic diversity and phylogeography of the species using sequences of the trnT-trnL intergenic spacer from 106 individuals belonging to 15 populations. We detected high within-species genetic diversity and strong among- population differentiation, but no evidence for phylogeographic structure. A haplotype network supported the occurrence of three main clades, the ancestral one being geographically restricted to the Gennargentu massif in Sardinia, while the two derived ones were relatively widespread. Coalescent-based analyses indicated deep divergence ti…

mtDNA diversity in rabbit population from Sicily (Italy)

2017

The European rabbit Oryctolagus cuniculus (O.c) lives all over the world and it represents an important resource for many predators. It has been classified as a Near-Threatened species in the Red List of Vertebrates of Italy. It is present in mediterranean basin as two known subspecies: O.c. cuniculus and O.c. algirus. The mediterranean geographic distribution of the two subspecies is still not well known. In particular, in Sicily, lacking of deep studies, is based on the body size and morphological characteristics; there wasn’t a complete description of the actual existing subspecies and previous studies only reported the morphological characteristics of the sicilian rabbit population. In …

Maintenance costs of male dominance and sexually antagonistic selection in the wild

2018

Variation in dominance status determines male mating and reproductive success, but natural selection for male dominance can be detrimental or antagonistic for female performance, and ultimately their fitness. Attaining and maintaining a high dominance status in a population of competing individuals is physiologically costly for males. But how male dominance status is mediated by maintenance energetics is currently not well understood, nor are the corresponding effects of male energetics on his sisters recognized. We conducted laboratory and field experiments on rodent populations to test whether selective breeding for male dominance status (dominant vs. subordinate breeding lines) antagonis…

FOUNDER-FLUSH SPECIATION IN DROSOPHILA PSEUDOOBSCURA: A LARGE-SCALE EXPERIMENT.

1993

A founder-flush-crash model of speciation has been proposed that may particularly apply to island and other colonizations. Previous laboratory experiments testing the model have given inconsistent results. We have conducted a large experiment with Drosophila pseudoobscura designed to meet the essential postulates of the model and to separately test some of the postulates. Forty-five experimental and 12 control populations have been studied during seven successive founder-flush-crash cycles, or about 50 generations. Sexual isolation tests yield significantly positive assortative mating in a few tests between pairs of experimental populations. Populations with fewer founders (N = 1 or 3) yiel…

2019

Hosts are typically infected with multiple strains or genotypes of one or several parasite species. These infections can take place simultaneously, but also at different times, i.e. sequentially, when one of the parasites establishes first. Sequential parasite dynamics are common in nature, but also in intensive farming units such as aquaculture. However, knowledge of effects of previous exposures on virulence of current infections in intensive farming is very limited. This is critical as consecutive epidemics and infection history of a host could underlie failures in management practices and medical intervention of diseases. Here, we explored effects of timing of multiple infections on vir…

Selection for multicomponent mimicry: equal feature salience and variation in preferred traits

2016

When should multiple traits on Batesian mimics be selected to resemble corresponding traits on model species? Here, we explore two possibilities. First, features of equal salience to predators may be used to categorize prey, selecting for multicomponent mimicry. Second, if different predators use single yet different traits to categorize prey, multicomponent mimicry may still be selected. We studied how blue tits categorized rewarding and unrewarding artificial prey items that are differentiated by a combination of two color dimensions. Many birds used both color dimensions to make decisions, and overall, the population selected for multicomponent mimicry. However, a subset of birds used on…

Karyotype variability and inter-population genomic differences in freshwater ostracods (Crustacea) showing geographical parthenogenesis

2018

Transitions from sexual to asexual reproduction are often associated with polyploidy and increased chromosomal plasticity in asexuals. We investigated chromosomes in the freshwater ostracod species Eucypris virens (Jurine, 1820), where sexual, asexual and mixed populations can be found. Our initial karyotyping of multiple populations from Europe and North Africa, both sexual and asexual, revealed a striking variability in chromosome numbers. This would suggest that chromosomal changes are likely to be accelerated in asexuals because the constraints of meiosis are removed. Hence, we employed comparative genomic hybridization (CGH) within and among sexual and asexual populations to get insigh…