Recent Distribution Patterns Research Articles

Biogeography of the Limacoidea sensu lato (Gastropoda: Stylommatophora): vicariance events and long‐distance dispersal

AbstractAim Reconstruction of the historical biogeography of the Limacoidea sensu lato (including the Staffordiidae, Dyakiidae, Gastrodontoidea, Parmacelloidea, Zonitidae, Helicarionoidea and Limacoidea). Evaluation of the relative importance of dispersal and its consequences.Location World‐wide.Methods Weighted ancestral area analysis.Results The ancestral areas of the individual clades have been delimited using weighted ancestral area analysis and a sequence of possible vicariance and dispersal events has been suggested. The results of the ancestral area analysis have tentatively been correlated with Cretaceous and Tertiary palaeogeography. The widely overlapping distribution patterns of several families of the Limacoidea testify to extensive dispersal events. Dispersal capacity of land snails is correlated with body size. The significant negative correlation between body size and distribution area size corroborates the importance of passive dispersal for the evolution of the distribution patterns.Main conclusions The existence of extensive dispersal events of poor active dispersers like land snails diminishes the importance of recent distribution patterns for the reconstruction of palaeogeography. On the other hand, dispersal ensures that biogeographical data reflect the geographical configurations at a given time and renders the use of palaeobiogeographic data for the reconstruction of palaeogeographic configurations of the respective age possible.

Platinum-Group-Metals (PGM) emitted from automobile catalytic converters and their distribution in roadside soils

The use of catalytic converters yields emissions of Pt, Rh and Pd. Geochemical background values, recent environmental concentrations and distribution patterns of these noble metals are very poorly known. In this paper a typical distribution of Pt, Rh and Pd in roadside soil is compared to the distribution of Pb and Zn. The effect of a barrier on airborne transport of aerosols is demonstrated as well as the influence of prevailing wind direction. Urban road-dusts are more likely to be inhaled than soil particles, therefore PGM-concentrations and their dependency on traffic intensity in road-dusts and soil was investigated. The importance of traffic-related emission for PGM-contents in sewage sludge is estimated based on the characteristic Pt/Rh ratio.

Die postglaziale Besiedlung Mitteleuropas durch Libellen, mit besonderer Berücksichtigung Südwestdeutschlands (Insecta, Odonata). The postglacial colonization of Central Europe by dragonflies, with special reference to southwestern Germany (Insecta, Odonata)

The migratory routes along which the Central European species of dragonflies probably immigrated from their periglacial refuges into Central Europe are reconstructed. Due to the topographical configuration in Central Europe, the postglacial invasions were confined to only a few routes. Mountain chains and also small river valleys, i.e. the Rhine valley between Lake Constance and Waldshut, acted as barriers; while geotectonic depressions, such as the ‘Geneva Gate’, ‘Burgundian Gate’ and ‘Moravian Gate’, played an important role as ‘gateways’ in overcoming these obstacles, the wide river plains were used as corridors to invade the hinterland. The extent of the immigration into Central Europe by the dragonfly species depended on the one hand on the distances which had to be covered from the refugial areas, but, on the other hand, also on the distinct postglacial climatic periods (Preboreal, Boreal, Atlantic, Subboreal, Subatlantic). Depending on their thermal requirements each species started expanding from their refugial areas at different times. Due to variable postglacial climatic conditions, progressive migratory phases alternated with regressive phases. The very different recent distribution patterns of the Central European dragonflies can only be understood if all the climate history, landscape morphology, the thermal requirements of the species, their origin (refugial areas) and history of colonization are considered. Because many Central European dragonfly localities currently lie at the periphery of the range of many species, these species can only survive in these areas if individual ‘reinforcements’ from their centres of distribution are possible. They still take place mainly along the old routes. Thus, disruption of the migratory routes, especially at the gateways, due to anthropogenic actions may influence the fauna of large Central European regions. Due to many anthropogenic influences, the routes already often seem to be interrupted over long distances and the connections to the centre of distribution already broken. As a result of precise knowledge of the courses of the migratory routes a better prediction is possible as to whether species conservation measures or recolonization projects will be successful.

The significance of high-boreal to subarctic maerl deposits in northern Norway to reconstruct holocene climatic changes and sea level oscillations

This paper describes (i) the Recent distribution pattern of various types of carbonate sediments in Troms county (northern Norway), and (ii) the onset of carbonate sedimentation after the final deglaciation of the Fennoscandian ice-shield. The distribution of major facies belts is strongly dependent on hydrographic and topographic constraints. The main bulk of carbonate deposits is derived from maerl-producing coralline algal biotopes that are restricted to the photic zone of waveprotected areas and influenced by tidal currents. Furthermore, extended mollusc and echinoderm-rich arenites are present in the area investigated. In deeper subtidal areas, terrigenous sediments of Late Weichselian to Early Holocene age are preserved. However, these are strongly influenced by later winnowing processes, generating a coquina lag deposit that serves as a secondary hardground for a diverse fouling community. The Holocene facies successions can be seen in several raised outcrops, containing the transition from glacigenic to Recent non-glacigenic depositional conditions. Autochthonous radiocarbon dated rhodolith banks, which mark the onset of carbonate sedimentation, yielded surprisingly young ages of 5,500 YBP. Around 5,500 YBP, present-day oceanographic and climatic conditions had already been firmly established. This time-lag can be explained with the behaviour of postglacial sea level fluctuations in the area. From 10,000 their cooperation in this project. We address our sincere thanks specifically to Prof. T.O. Vorren, Dr. M. Hald, Dr. B. Gulliksen, Dr. J. Hansen, Dr. J.J. Moller, Dr. E. Thomsen, and Dr. G. Corner for their dedicate help in organizing our field trips in Troms and for extensive scientific discussions. Special thanks to capitain K. Bendiksen for his patience and professional skill while operating the vessel ‘OTTAR’ in the skerry area even under bad weather conditions. S. Rasmussen and G. Ellingsen assisted during the cruises and very kindly introduced us to the Norwegian way of life. Special thanks to the two reviewers (Prof. Dr. W.-Ch. Dullo and anonymus) for their critical but constructive remarks. J. Welling and Dr. M. Kaminski improved the language of the final version of the manuscript. This project is part of the German Science Foundation’s main research program ‘Globale und regionale Steuerungsprozesse biogener Sedimentation”. Financial support was kindly provided by the Deutsche Forschungs-gemeinschaft (He 1671/1-1, 2).

Recent Benthonic Foraminiferal Biofacies in the Arctic Ocean

Analysis of Recent foraminiferal distribution patterns for the Amerasian Basin and the adjacent continental shelves indicate 3 major biofacies: the Trochammina nana biofacies (17-350 m), the Cassidulina teretis biofacies (350-900 m) and the Stetsonia horvathi biofacies (below 900 m), with the T. nana and S. horvathi biofacies divided into subfacies. Water mass properties appear to play the dominant role in controlling the distribution of the biofacies. Recent benthonic foraminiferal biofacies in the Arctic Ocean

Jahreszeitliche Verteilungsmuster heterotropher Bakterien, bakterieller Fäkalindikatoren und der gelösten organischen Substanz im Bodensee (Obersee und Überlinger See)

Concomitant with the increased eutrophication observed during the last 20 years in Lake of Constance, also an increase of saprobity was expected. To prove this, viable counts of zymogenic heterotrophic bacteria (TVC) as well as of fecal indicators were determined in vertical profiles during the cycle of a year and compared with concomitant concentrations of dissolved organic matter (DOM). There was an inverse relationship between DOM and epilimnetic peaks of TVC, but also between DOM and viable counts of Cytophagaceae, which were most abundant at low water temperatures. The average epilimnetic TVC-values exceeded comparable 20 years old data by a factor of 10. On the other hand, fecal Coli and Streptococci, by accumulating in the bottom water, showed mostly a distribution which was reverse to earlier findings of this group and recent distribution patterns of TVC as well. Altogether, the results support the view that the abundance of zymogenic bacteria in Lake of Constance is mainly controlled by its epilimnetic primary production of degradable organic matter.

Recent mollusc distribution patterns and palaeobathymetry, southeastern Beaufort Sea

Molluscs were obtained from 515 of the 657 grab samples collected 1970–1972 inclusive from southeastern Beaufort Sea, from 29 of the 46 cores taken in the area, and from raised marine deposits at Kay Point and on Herschel Island, Yukon Territory. One hundred and one species have been identified. Water depth was apparently the major factor controlling species distribution. Holocene sea levels, determined by comparing core faunas with the established depth ranges for living specimens, are considered to be reasonably accurate for near-shore sites, but yield excessively shallow water depth figures for deep stations (outer shelf and slope). The anomalous results are probably related to offshore transport of shallow water species.

The Biogeography of Enid Landsnails on the Aegean Islands

The distribution in the Aegean archipelago of one family of landsnails, the Enidae, is described. The relationship between the number of species on an island and (i) the island's area, (ii) the island's distance from the nearest mainland, and (iii) mean size of each species, is examined. The number of species per island is not correlated significantly with any of these three factors. There is a good correlation between the distribution of landsnails and the topography beneath sea level around the island. Some species are found only off the coasts of Turkey or of Greece, on islands included within the 100 fathom isobath; one subspecies is found on twenty-four islands, all within the area included within the 200 fathom (364 m) isobath; and other species are found on those islands which lie beyond the 200 fathom (364 m) isobath. This suggests that, rather than representing island biogeography in its dynamic sense (recent dispersal over a hostile habitat), the recent Enid fauna represents a relict continental biogeography (past dispersal over a continuous, non-hostile habitat), and that such continental dispersal occurred in periodY when, as the relative level of the sea dropped as compared to that of today, isolation between certain islands, was abolished. The known geological history of the Aegean archipelago agrees well with such an hypothesis. From the recent distribution pattern it appears that the Enidae invaded the Aegean in three distinct waves, corresponding to three different past sea-levels. The fact that over 800% of the sixty-three islands, regardless of each island's area or proximity to mainland, have only one species of Enid each, whereas Turkey is inhabited by fifty-five Enids, suggests that today there is almost no immigration from the Turkish mainland. There also appears to be no immigration from Greece. The fact, on the other hand, that almost every Aegean island, down to the most remote and minute of these, is inhabited by Enidae of one species or another, suggests that the rate of extinction is very low. The number of species on an island thus appears to be the combined result of almost no immigration and almost no extinction.