200 research outputs found
Bolboforma (Protophyta,incertae sedis) im OligozÀn und MiozÀn des Mediterran und der Zentralen Paratethys
Aus oligozÀnen und miozÀnen Sedimenten im Ablagerungsraum der Zentralen Paratethys, aus
DSDP Bohrungen von Leg 42 A und ODP Leg 107 im Mediterran sowie aus AufschlĂŒssen in Algerien
und Mittelspanien werden Arten und Zysten von Bolboforma (Protophyta, incertae sedis)
nachgewiesen. Die publizierten Vorkommen wurden revidiert und in die Auswertung einbezogen.
Dadurch konnten die bisherigen Kenntnisse ĂŒber die stratigraphische und palĂ€oökologische
Verbreitung dieser wahrscheinlich planktonischen Mikrofossilgruppe im Zeitabschnitt OberoligozÀn
bis ObermiozÀn ergÀnzt werden. In der Zentralen Paratethys ist das OberoligozÀn und tiefere
UntermiozÀn (Egerien bis Eggenburgien) durch Bolboforma rotunda und B. spinosa gekennzeichnet.
Im höheren UntermiozÀn wurde Bolboforma nicht nachgewiesen. Sehr reiche Vorkommen
charakterisieren das MittelmiozÀn (Badenien) und gestatten eine Unterteilung in die B. reticulataund
die B. badenesis-Zone. Die im Atlantik dazwischen liegende, zeitlich sehr kurze B. danielsi-Zone
wurde hier und auch im Mediterran bisher nicht beobachtet. Mit der Reduktion der SalinitÀt ab dem
Sarmatien verschwinden Bolboformen aus der Paratethys. Im Mediterran wurde Bolboforma erst ab
dem MittelmiozÀn nachgewiesen. Die B. reticulata-, B. badenensis- und B. compressispinosa-Zonen sind
im MittelmiozÀn vorhanden. Im ObermiozÀn sind Nachweise von B. laevis und B. aculeata im
Tortonien sowie von B. subfragoris im Tortonien und Messinien zu erwĂ€hnen. FĂŒr Korrelationen wichtig
ist die Beobachtung der B. intermedia-Zone im unteren Messinien (NN lib) der Tyrrhenischen See,
sowie das Vorkommen von B. metzmacheri in AufschlĂŒssen Algeriens. Das faziesbrechende
Vorkommen von Bolboforma ist besonders hervorzuheben
Statistical analysis of Neogene sediment thickness deposited during the first transtensional and first transpressional evolutionary stages in the Bjelovar Sub-basin, Northern Croatia
Reconciling Deep Calibration and Demographic History: Bayesian Inference of Post Glacial Colonization Patterns in Carcinus aestuarii (Nardo, 1847) and C. maenas (Linnaeus, 1758)
A precise inference of past demographic histories including dating of demographic events using Bayesian methods can only be achieved with the use of appropriate molecular rates and evolutionary models. Using a set of 596 mitochondrial cytochrome c oxidase I (COI) sequences of two sister species of European green crabs of the genus Carcinus (C. maenas and C. aestuarii), our study shows how chronologies of past evolutionary events change significantly with the application of revised molecular rates that incorporate biogeographic events for calibration and appropriate demographic priors. A clear signal of demographic expansion was found for both species, dated between 10,000 and 20,000 years ago, which places the expansions events in a time frame following the Last Glacial Maximum (LGM). In the case of C. aestuarii, a population expansion was only inferred for the Adriatic-Ionian, suggestive of a colonization event following the flooding of the Adriatic Sea (18,000 years ago). For C. maenas, the demographic expansion inferred for the continental populations of West and North Europe might result from a northward recolonization from a southern refugium when the ice sheet retreated after the LGM. Collectively, our results highlight the importance of using adequate calibrations and demographic priors in order to avoid considerable overestimates of evolutionary time scales
Contrasting Geographical Distributions as a Result of Thermal Tolerance and Long-Distance Dispersal in Two Allegedly Widespread Tropical Brown Algae
BackgroundMany tropical marine macroalgae are reported from all three ocean basins, though these very wide distributions may simply be an artifact resulting from inadequate taxonomy that fails to take into account cryptic diversity. Alternatively, pantropical distributions challenge the belief of limited intrinsic dispersal capacity of marine seaweeds and the effectiveness of the north-south oriented continents as dispersal barriers. We aimed to re-assess the distribution of two allegedly circumtropical brown algae, Dictyota ciliolata and D. crenulata, and interpret the realized geographical range of the respective species in relation to their thermal tolerance and major tectonic and climatic events during the Cenozoic.Methodology/Principal FindingsSpecies delimitation was based on 184 chloroplast encoded psbA sequences, using a Generalized Mixed Yule Coalescent method. Phylogenetic relationships were inferred by analyzing a six-gene dataset. Divergence times were estimated using relaxed molecular clock methods and published calibration data. Distribution ranges of the species were inferred from DNA-confirmed records, complemented with credible literature data and herbarium vouchers. Temperature tolerances of the species were determined by correlating distribution records with local SST values. We found considerable conflict between traditional and DNA-based species definitions. Dictyota crenulata consists of several pseudocryptic species, which have restricted distributions in the Atlantic Ocean and Pacific Central America. In contrast, the pantropical distribution of D. ciliolata is confirmed and linked to its significantly wider temperature tolerance.Conclusions/SignificanceTectonically driven rearrangements of physical barriers left an unequivocal imprint on the current diversity patterns of marine macroalgae, as witnessed by the D. crenulataâcomplex. The nearly circumglobal tropical distribution of D. ciliolata, however, demonstrates that the north-south oriented continents do not present absolute dispersal barriers for species characterized by wide temperature tolerances
First description of a fossil chamaeleonid from Greece and its relevance for the European biogeographic history of the group
The fossil record of Chamaeleonidae is very scarce and any new specimen is therefore considered important for our understanding of the evolutionary and biogeographic history of the group. New specimens from the early Miocene of Aliveri (Evia Island), Greece constitute the only fossils of these lizards from southeastern Europe. Skull roofing material is tentatively attributed to the Czech species Chamaeleo cf. andrusovi, revealing a range extension for this taxon, whereas tooth-bearing elements are described as indeterminate chamaeleonids. The Aliveri fossils rank well among the oldest known reptiles from Greece, provide evidence for the dispersal routes of chameleons out of Africa towards the European continent and, additionally, imply strong affinities with coeval chamaeleonids from Central Europe
Climate-driven range extension of Amphistegina (protista, foraminiferida) : models of current and predicted future ranges
© The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS ONE 8 (2013): e54443, doi:10.1371/journal.pone.0054443.Species-range expansions are a predicted and realized consequence of global climate change. Climate warming and the poleward widening of the tropical belt have induced range shifts in a variety of marine and terrestrial species. Range expansions may have broad implications on native biota and ecosystem functioning as shifting species may perturb recipient communities. Larger symbiont-bearing foraminifera constitute ubiquitous and prominent components of shallow water ecosystems, and range shifts of these important protists are likely to trigger changes in ecosystem functioning. We have used historical and newly acquired occurrence records to compute current range shifts of Amphistegina spp., a larger symbiont-bearing foraminifera, along the eastern coastline of Africa and compare them to analogous range shifts currently observed in the Mediterranean Sea. The study provides new evidence that amphisteginid foraminifera are rapidly progressing southwestward, closely approaching Port Edward (South Africa) at 31°S. To project future species distributions, we applied a species distribution model (SDM) based on ecological niche constraints of current distribution ranges. Our model indicates that further warming is likely to cause a continued range extension, and predicts dispersal along nearly the entire southeastern coast of Africa. The average rates of amphisteginid range shift were computed between 8 and 2.7 km yearâ1, and are projected to lead to a total southward range expansion of 267 km, or 2.4° latitude, in the year 2100. Our results corroborate findings from the fossil record that some larger symbiont-bearing foraminifera cope well with rising water temperatures and are beneficiaries of global climate change.This work was supported by grants from the German Science Foundation (DFG; www.dfg.de) to ML and SL (LA 884/10-1, LA 884/5-1)
Paleogeographic evolution of the Southern Pannonian Basin: 40Ar/39Ar age constraints on the Miocene continental series of notthern Croatia
The Pannonian Basin, originating during the
Early Miocene, is a large extensional basin incorporated
between Alpine, Carpathian and Dinaride fold-thrust belts.
Back-arc extensional tectonics triggered deposition of up to
500-m-thick continental fluvio-lacustrine deposits distributed
in numerous sub-basins of the Southern Pannonian
Basin. Extensive andesitic and dacitic volcanism accompanied
the syn-rift deposition and caused a number of
pyroclastic intercalations. Here, we analyze two volcanic
ash layers located at the base and top of the continental
series. The lowermost ash from Mt. Kalnik yielded an
40Ar/39Ar age of 18.07 ± 0.07 Ma. This indicates that the
marine-continental transition in the Slovenia-Zagorje
Basin, coinciding with the onset of rifting tectonics in the
Southern Pannonian Basin, occurs roughly at the Eggenburgian/
Ottnangian boundary of the regional Paratethys
time scale. This age proves the synchronicity of initial
rifting in the Southern Pannonian Basin with the beginning
of sedimentation in the Dinaride Lake System. Beside
geodynamic evolution, the two regions also share a biotic
evolutionary history: both belong to the same ecoregion,
which we designate here as the Illyrian Bioprovince. The
youngest volcanic ash level is sampled at the Glina and
Karlovac sub-depressions, and both sites yield the same
40Ar/39Ar age of 15.91 ± 0.06 and 16.03 ± 0.06 Ma,
respectively. This indicates that lacustrine sedimentation in
the Southern Pannonian Basin continued at least until the
earliest Badenian. The present results provide not only
important bench marks on duration of initial synrift in the
Pannonian Basin System, but also deliver substantial
backbone data for paleogeographic reconstructions in
Central and Southeastern Europe around the EarlyâMiddle
Miocene transition
The genetic diversity, phylogeography and morphology of Elphidiidae (Foraminifera) in the Northeast Atlantic
Genetic characterisation (SSU rRNA genotyping) and Scanning ElectronMicroscope (SEM) imaging of individualtests were used in tandem to determine the modern species richness of the foraminiferal family Elphidiidae(Elphidium, Haynesina and related genera) across the Northeast Atlantic shelf biomes. Specimens were collectedat 25 locations fromthe High Arctic to Iberia, and a total of 1013 individual specimenswere successfully SEMimagedand genotyped. Phylogenetic analyses were carried out in combination with 28 other elphidiid sequencesfrom GenBank and seventeen distinct elphidiid genetic types were identified within the sample set, sevenbeing sequenced for the first time. Genetic types cluster into sevenmain cladeswhich largely represent their generalmorphologicalcharacter. Differences between genetic types at the genetic, morphological and biogeographiclevels are indicative of species level distinction. Their biogeographic distributions, in combination with elphidiidSSU sequences from GenBank and high resolution images from the literature show that each of them exhibitsspecies-specific rather than clade-specific biogeographies. Due to taxonomic uncertainty and divergent taxonomicconcepts between schools, we believe that morphospecies names should not be placed onto molecularphylogenies unless both the morphology and genetic type have been linked to the formally named holotype,or equivalent. Based on strictmorphological criteria,we advocate using only a three-stage approach to taxonomyfor practical application in micropalaeontological studies. It comprises genotyping, the production of a formalmorphological description of the SEM images associated with the genetic type and then the allocation of themost appropriate taxonomic name by comparison with the formal type description. Using this approach, wewere able to apply taxonomic names to fifteen genetic types. One of the remaining two may be potentially cryptic,and one is undescribed in the literature. In general, the phylogeographic distribution is in agreement with ourknowledge of the ecology and biogeographical distribution of the corresponding morphospecies, highlighting thegenerally robust taxonomic framework of the Elphidiidae in time and space
- âŠ