Search results for "Arctic"
showing 10 items of 565 documents
Bacterioplankton Community Composition Along Environmental Gradients in Lakes From Byers Peninsula (Maritime Antarctica) as Determined by Next-Genera…
2019
This study comprises the first attempt to describe the planktonic bacterial communities of lakes from Byers Peninsula, one of the most significant limnological districts in the Maritime Antarctica, leveraging next-generation sequencing (NGS) technologies. For the survey, we selected 7 lakes covering the environmental gradient from inland to coastal lakes, some of them sampled both in surface and deep waters. Analysis provided just over 85,000 high quality sequences that were clustered into 864 unique Zero-radius Operational Taxonomic Units (ZOTUs) (i.e., 100% sequence similarity). Yet, several taxonomic uncertainties remained in the analysis likely suggesting the occurrence of local bacteri…
Functional Metabolic Diversity of Bacterioplankton in Maritime Antarctic Lakes
2021
A summer survey was conducted on the bacterioplankton communities of seven lakes from Byers Peninsula (Maritime Antarctica), differing in trophic and morphological characteristics. Predictions of the metabolic capabilities of these communities were performed with FAPROTAX using 16S rRNA sequencing data. The versatility for metabolizing carbon sources was also assessed in three of the lakes using Biolog Ecoplates. Relevant differences among lakes and within lake depths were observed. A total of 23 metabolic activities associated to the main biogeochemical cycles were foreseen, namely, carbon (11), nitrogen (4), sulfur (5), iron (2), and hydrogen (1). The aerobic metabolisms dominated, althou…
Clima subártico para os primeiros Homo sapiens na Europa
2021
Description
Molecular phylogeny of the harvestmen genus Sabacon (Arachnida: Opiliones: Dyspnoi) reveals multiple Eocene–Oligocene intercontinental dispersal even…
2012
Abstract We investigated the phylogeny and biogeographic history of the Holarctic harvestmen genus Sabacon , which shows an intercontinental disjunct distribution and is presumed to be a relatively old taxon. Molecular phylogenetic relationships of Sabacon were estimated using multiple gene regions and Bayesian inference for a comprehensive Sabacon sample. Molecular clock analyses, using relaxed clock models implemented in BEAST, are applied to date divergence events. Biogeographic scenarios utilizing S-DIVA and Lagrange C++ are reconstructed over sets of Bayesian trees, allowing for the incorporation of phylogenetic uncertainty and quantification of alternative reconstructions over time. F…
Palaeoclimatic changes explain Anatolian mountain frog evolution: a test for alternating vicariance and dispersal events
2002
Holarctic biodiversity has been influenced by climatic fluctuations since the Pliocene. Asia Minor was one of the major corridors for postglacial invasions in the Palearctic. Today this area is characterized by an extraordinarily rich fauna with close affiliation to European, Asian and Indo-African biota. However, exact scenarios of range expansion and contraction are lacking. Using a phylogeographical approach we (i) identify monophyletic lineages among Anatolian mountain frogs and (ii) derive a spatio-temporal hypothesis for the invasion process in Anatolia. We sequenced 540 bp of the mitochondrial 16S rRNA gene from 40 populations of mountain frogs from Anatolia, the Elburz Mountains and…
Description of Dryocosmus destefanii new species (Hymenoptera: Cynipidae: Cynipini) from Quercus suber L. in Italy
2018
A new species, Dryocosmus destefanii Cerasa & Melika n. sp. associated with a Cerris section oak, Quercus suber L., is described from Italy. Description, diagnosis, host associations and biology for the new species and an illustrated identification key to the Western Palaearctic Dryocosmus species are given. The description is supported by morphological and molecular data.
Temnothorax pilagens sp. n. – a new slave-making species of the tribe Formicoxenini from North America (Hymenoptera, Formicidae)
2014
A new species of the ant genus Temnothorax Forel, 1890 – Temnothorax pilagens sp. n. is described from eastern North America. T. pilagens sp. n. is an obligate slave-making ant with two known hosts: T. longispinosus (Roger, 1863) and T. ambiguus (Emery, 1895). A differential diagnosis against Temnothorax duloticus (Wesson, 1937), the other dulotic congener from the Nearctic, is presented and a biological characteristics of the new species is given.
Use of Quantitative Morphological Analysis Combined with a Large Sample Size for Estimating Morphological Variability in a Case Study of Armoured Mit…
2015
Abstract The morphology of Oribatida and similar little-known groups of organisms varies considerably, which complicates morphological analysis (e.g. species descriptions). Qualitative analyses have been carried out mostly on a small number of individuals (n < 25). There is lack of studies dealing with mechanisms of how that variation can change in relation to sample size and insufficient discussion on whether qualitative or quantitative analysis is more appropriate for description of morphological variability. A total of 500 adult Carabodes subarcticus Trägårdh, 1902 Oribatida were collected from a local population. Six qualitative and six quantitative traits were characterised using li…
Geographic variation of the Greater white-toothed shrew (Crocidura russula Hermann, 1780 Mammalia, Soricidae)
1996
A multivariate morphometric study of the Greater white-toothed shrew (C. russula) throughout its Palearctic range was carried out to search for patterns of geographic variation within the species boundary. Burnaby's and multiple group principal component analysis allowed the adjustment of raw data with respect to within-sample allometric variation. Multivariate 'size-free' results show a stepped cline with the phenotypical trait reduction and shape change from the eastern to the western Maghreb. Pleistocene fossil mandibles proved to have low phenetic distances with eastern populations (Tunisia, east Algeria) and it is argued that their character set is the primitive condition. The ancestra…
Sources of nitrous oxide and fate of mineral nitrogen in sub-Arctic permafrost peat soils
2021
Nitrous oxide (N2O) emissions from permafrost-affected terrestrial ecosystems have received little attention, largely because they have been thought to be negligible. Recent studies, however, have shown that there are habitats in subarctic tundra emitting N2O at high rates, such as bare peat surfaces on permafrost peatlands. The processes behind N2O production in these high-emitting habitats are, however, poorly understood. In this study, we established an in situ 15N-labelling experiment with the main objectives to partition the microbial sources of N2O emitted from bare peat surfaces (BP) on permafrost peatlands and to study the fate of ammonium and nitrate in these soils and in adjacent …