Search results for " speciation"
showing 10 items of 272 documents
Diversification and community assembly of the world’s largest tropical island
2022
Aim: The species diversity and endemism of tropical biotas are major contributors to global biodiversity, but the factors underlying the formation of these systems remain poorly understood. Location: The world's largest tropical island, New Guinea. Time period: Miocene to present. Major taxa studied: Passerine birds. Methods: We first generated a species-level phylogeny of all native breeding passerine birds to analyse spatial and elevational patterns of species richness, species age and phylogenetic diversity. Second, we used an existing dataset on bill morphology to analyse spatial and elevational patterns of functional diversity. Results: The youngest New Guinean species are principally …
Mn, Fe, Zn and As speciation in a fast-growing ferromanganese marine nodule
2004
The speciation of Mn, Fe, As and Zn in a fast-growing (0.02mm/yr), shallow-marine ferromanganese nodule has been examined by micro X-ray fluorescence, micro X-ray diffraction, and micro X-ray absorption spectroscopy. This nodule exhibits alternating Fe-rich and Mn-rich layers reflecting redox variations in water chemistry. Fe occurs as two-line ferrihydrite. The As is strictly associated with Fe and is mostly pentavalent, with an environment similar to that of As sorbed on or coprecipitated with synthetic ferrihydrite. The Mn is in the form of turbostratic birnessite with ~;10 percent trivalent manganese in the layers and probably ~;8 percent corner-sharing metal octahedra in the interlayer…
The structure of parasite component communities in brackish water fishes of the northeastern Baltic Sea
2001
We used nestedness analysis to seek non-random patterns in the structure of component communities of metazoan parasites collected from 31 sympatric fish species from the northeastern Bothnian Bay, the most oligohaline area of the Baltic Sea. Only 8 marine parasite species were found among the 63 species recorded, although some marine fish species reproduce in the bay and others occasionally visit the area. Marine parasite species can utilize both freshwater and marine fish species as intermediate or final hosts, and marine fish can harbour freshwater parasite species. This exchange of parasite species between marine and freshwater fish has probably resulted from ecological factors acting ov…
Analytical method for PAHs chemical speciation in sediments
2008
The aim of this work is to optimize a method to examine the PAHs chemical speciation during the aging of sediments that is important in order to known the toxicological risk of a polluted area. In particular, we have conducted this research in order to determine if the organic contaminants fate is dependent to sediment characteristics and to study the potential role of humin and alkaline-extractable humic substances in the sequestration of PAHs in sediment. The Polycyclic Aromatic Hydrocarbons (PAHs) include molecules containing fused aromatic rings and are of special concern because of their widespread distribution throughout the environment and their often toxic and carcinogenic propertie…
Parallel evolution of flower reduction in two alpineSoldanellaspecies (Primulaceae)
2014
The European endemic Soldanella has traditionally been divided into two morphologically well-defined sections. Section Tubiflores contains two species growing in high-elevation habitats, whereas most of the 14 species of section Soldanella inhabit montane forests. Section Tubiflores has a reduced floral morphology compared with section Soldanella. A previous phylogenetic study based on internal transcribed spacer (ITS) and AFLP data has revealed that, although the genus Soldanella itself is monophyletic, both sections are paraphyletic. Soldanella alpina (section Soldanella) forms a clade with S. minima and S. pusilla (section Tubiflores), and the grouping of S. alpina with S. pusilla has be…
Phylogeny and quaternary history of the European montane/alpine endemicSoldanella(Primulaceae) based on ITS and AFLP variation
2001
Soldanella contains 16 species of herbaceous perennials that are endemic to the central and south European high mountains. The genus is ecogeographically subdivided into forest/montane and alpine species. Evolutionary relationships and large-scale biogeographic patterns were inferred from parsimony analyses of the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA, and genetic distance analyses based on amplified fragment length polymorphism (AFLP) markers. The ITS region proved useful for examining subgeneric relationships and testing hypotheses on genus-wide divergence times, whereas the AFLP markers were suitable for studying relationships among closely related taxa and b…
Microevolution of eastern palaearctic Grey tits as indicated by their vocalizations (Parus [Poecile]: Paridae, Aves) I. Parus montanus: Contributions…
2009
Within the Palaearctic Region, the Willow tit (Parus montanus) displays four vicariant forms of territorial song. 1. “Alpine” form (pure single-frequency whistles, Fig. 5: 1) in the Alps and adjacent mountains to the East. 2. “Lowland” or “Normal” form (frequency change from high to low within one note, Fig. 5: 2) in the other parts of NW, Central and SE Europe. 3. In populations of N and E Europe as well as of W and E Siberia every individual bird uses - so far as known - both song types; this “Siberian” form (Figs. 1, 2) includes intergrades (Fig. 3). The comparatively type-rich Siberian repertoire is found in a vast area from N and E Europe to the Amur River and Ussuriland in Siberia. 4.…
Arsenic Sorption onto Peat and Iron Humates
2012
Environmental pollution with arsenic is a global problem; therefore, new remediation methods are needed. Peat modified with iron compounds and iron humates were prepared and tested for sorption of arsenic compounds. The highest sorption capacity was observed when iron-modified peat was used. Sorption of different arsenic speciation forms onto iron-modified peat sorbents was investigated as a function of pH, reaction time and temperature. Sorption capacity increases with temperature and was spontaneous and endothermic.
Spatial and Temporal Patterns in the Evolution of the Flora of the European Alpine System
2003
This paper presents a perspective of how phylogenetic and phylogeographic hypotheses, based on nuclear DNA sequence variation (ITS) or amplified fragment length polymorphisms (AFLPs), can provide insights into the origin and evolution of the European high mountain flora. We focus on a diversity of unrelated herbaceous plant taxa that are broadly co-distributed across the European Alpine System, representing different taxonomic levels, and having either Mediterranean or Asian affinities (i.e., Anthyllis montana, Pritzelago alpina, Globularia vs. Soldanella, and Primula sect. Auricula). Our observations highlight that all taxa investigated began to diversify at the beginning of the Pleistocen…
Origin of the natural variation in the storage of dietary carotenoids in freshwater amphipod crustaceans
2020
16 pages; International audience; Carotenoids are diverse lipophilic natural pigments which are stored in variable amounts by animals. Given the multiple biological functions of carotenoids, such variation may have strong implications in evolutionary biology. Crustaceans such as Gammarus amphipods store large amounts of these pigments and inter-population variation occurs. While differences in parasite selective pressure have been proposed to explain this variation, the contribution of other factors such as genetic differences in the gammarid ability to assimilate and/or store pigments, and the environmental availability of carotenoids cannot be dismissed. This study investigates the relati…