Search results for "evolution"
showing 10 items of 11096 documents
Legacy system evolution - A comparative study of modernisation and replacement initiation factors
2007
Decisions regarding information system evolution strategy become topical as the organisation’s information systems age and start to approach the end of their life cycle. An interview study was conducted in order to compare factors influencing modernisation and replacement initiation. System age, obsolete technology and high operation or maintenance costs were identified as triggers for both modernisation and replacement projects. The results show that the most prevalent individual reason for modernisation initiative is business development. Common initiation factors for replacement projects were end of vendor support and system’s inability to respond to organisation’s business needs. peerRe…
Chromosomal dynamics in platyrrhinae by mapping bacs probes
2012
molecular cytogenetics, cloned DNA probe, new evolutionary centromere, human synteny 4, phylogeny
Variation in the Sizes of Chthamalid Barnacle Post-Settlement Cyprids on European Shores
2001
As part of a wider study on the settlement and recruitment of Chthamalus spp. in Europe, this study investigated whether chthamalid cyprids can be separated by length on a European scale. Variation in cyprid length with latitude and temporal variation at selected localities were also examined. The lengths of cyprids collected between 1996-1999 on nine rocky shores in Europe are reported. Elminius modestus cyprids were found only at Roscoff, NW France and could be distinguished due to their Carapace shape and length. They showed a unimodal length distribution, measuring between 450 and 625 mum, with no variation in length between the two sampling dates (1997 and 1998). Based on carapace shap…
A new species within the Centaurea busambarensis complex (Asteraceae, Cardueae) from Sicily
2022
The Centaurea busambarensis group is made up by eight species endemic to Sicily. We statistically evaluated a population found on the Nebrodi Mountain (NE Sicily) to verify if the observed morphological differences with the already known taxa justified the description of a new one. It resulted in being sufficiently distinct to deserve recognition at the species level. Centaurea valdemonensis, a new species endemic to Sicily is described and illustrated here. It is confined to the Nebrodi Mountains (NE Sicily). The distinction of this taxon from the others belonging to the C. busambarensis complex has been supported with the aid of statistical analyses on morphological characters. The differ…
No phylogeographic structure in the circumpolar snowy owl (Bubo scandiacus)
2008
The snowy owl (Bubo scandiacus) is a nomadic species with a circumpolar distribution. It has recently declined in the western Palearctic and may thus be worthy of special consideration for conservation. We investigated genetic structure in three well separated geographic regions within the snowy owls’ breeding range. We sequenced two mitochondrial genes; the control region and cytochrome b, and two Z-chromosome introns; VLDLR-9 and BRM-15. We found no phylogeographic structure among the sampled regions, indicating high levels of gene flow in the recent past and possibly still today. Intra-population diversity did not vary between regions for the control region, but for Cyt b, North American…
Elucidating geological and biological processes underlying the diversification of Sulawesi tarsiers.
2009
Because of their exceptionally long independent evolution, a range diminution of their Eocene relatives, and a remarkable subsequent diversification in Southeast Asia, tarsiers are of particular importance to evolutionary primatologists. Little is known, however, on the processes shaping the radiation of these small enigmatic primates—especially on the Indonesian island of Sulawesi, their center of endemism. Geological reconstructions and progress in applying DNA sequence information to divergence dating now provide us with the tools and background to comprehend tarsier dispersal. Here, we describe effects of plate-tectonic movements, Pleistocene sea level changes, and hybridization on the…
Phylogeography of a Palaearctic sedentary passerine, the willow tit (Parus montanus)
2001
We analysed variation of the mitochondrial control region from willow tits through its Palaearctic distribution range. Although we found high amount of genetic variation (π=1.114%), there was almost no differentiation between subspecies or geographical localities. This may be because of a combination of several ecological and genetic factors, including a relatively homogenic habitat through the distribution range, lack of geographical barriers, high gene flow and a large long-term effective population size. On the contrary, in the songar tit, which is sometimes considered to be conspecific with the willow tit, the mitochondrial lineages seem to correlate with the geographical locality and a…
Environmental features of deep-sea habitats linked to the genetic population structure of a crustacean species in the Mediterranean Sea
2009
The deep-sea habitat, from 200 to 2000 m depth, has long been thought as an ecosystem where biotic and abiotic factors vary very little and consequently species are not disturbed by processes and phenomena which could promote fast evolutionary mechanisms. Unfortunately, biological information relating to deep water is limited, especially regarding the population genetics of species inhabiting the Mediterranean Sea, and general patterns cannot be inferred. In this study we report data on the population genetic structure of Aristeus antennatus, a deep-sea decapod crustacean species which has been widely studied due to its important economic value. We surveyed and examined the variation in a 3…
Prediction of harmful variants on mitochondrial genes : Test of habitat-dependent and demographic effects in a euryhaline fish
2017
Both effective population size and life history may influence the efficacy of purifying selection, but it remains unclear if the environment affects the accumulation of weakly deleterious nonsynonymous polymorphisms. We hypothesize that the reduced energetic cost of osmoregulation in brackish water habitat may cause relaxation of selective constraints at mitochondrial oxidative phosphorylation (OXPHOS) genes. To test this hypothesis, we analyzed 57 complete mitochondrial genomes of Pungitius pungitius collected from brackish and freshwater habitats. Based on inter- and intraspecific comparisons, we estimated that 84% and 68% of the nonsynonymous polymorphisms in the freshwater and brackish …
Genome-wide analysis of Italian sheep diversity reveals a strong geographic pattern and cryptic relationships between breeds
2014
Summary Italy counts several sheep breeds, arisen over centuries as a consequence of ancient and recent genetic and demographic events. To finely reconstruct genetic structure and relationships between Italian sheep, 496 subjects from 19 breeds were typed at 50K single nucleotide polymorphism loci. A subset of foreign breeds from the Sheep HapMap dataset was also included in the analyses. Genetic distances (as visualized either in a network or in a multidimensional scaling analysis of identical by state distances) closely reflected geographic proximity between breeds, with a clear north–south gradient, likely because of high levels of past gene flow and admixture all along the peninsula. Sa…