Western Mediterranean Europe Research Articles

The barriers to oceanic island radiation in bryophytes: insights from the phylogeography of the moss Grimmia montana

AbstractAim In contrast to angiosperms, bryophytes do not appear to have radiated in Macaronesia and the western Mediterranean. We evaluate if: (1) the apparent lack of radiation in bryophytes reflects our failure to recognize cryptic endemic species; (2) bryophytes are characterized by extremely low evolutionary rates; or (3) bryophytes have a high dispersal ability, which prevents genetic isolation.Location Worldwide, with a special emphasis on Macaronesia and the western Mediterranean.Methods Three chloroplast regions were sequenced from samples of the moss Grimmia montana from its entire distribution range. Network analyses, Fst and Nst statistics were used to describe and interpret the phylogeographical signal in the data.Results Despite significant phylogeographical signal in the chloroplast genome, which demonstrates limits to gene flow at the continental scale, repeated sister group relationships observed among accessions from different geographical areas suggest recurrent colonization patterns. These observations are consistent with mounting evidence that intercontinental distributions exhibited by many bryophyte species result from long‐distance dispersal rather than continental drift. Madeiran and western Mediterranean island haplotypes are either shared by, or closely related to, European and North American ones. Fst values between Madeira, western Mediterranean islands, North America and Europe are not significantly different from zero, and suggest that Madeira and the south‐western Mediterranean are subject to strong transatlantic gene flow. By contrast, haplotypes found in the Canary Islands are shared or closely related to those of populations from south‐western Europe or southern Africa.Main conclusions Multiple origins and colonization events are not consistent with the hypothesis of a relictual origin of the Macaronesian moss flora. One possible reason for the failure of taxa that experienced multiple colonization events to radiate is niche pre‐emption. We suggest that strong gene flow, coupled with the occupancy of all suitable niches, either by earlier conspecific colonizers or by other species, could be the mechanism preventing island radiation in G. montana and other cryptogams with high long‐distance dispersal abilities.

Life-history traits of alien and native senecio species in the Mediterranean region

Two related shrubs, Senecio inaequidens and S. pterophorus, both introduced to western Mediterranean Europe from South Africa, were compared with a native Mediterranean shrub, S. malacitanus, to identify life-history traits that confer invasive ability. We examined ecological interactions that affect seedling emergence and establishment, flowering time, growth and reproduction and competitive ability in these three closely related species. Seeds were planted, the seedlings were then transplanted and individual performance was evaluated with respect to: (1) competition with plant neighbours and (2) resource addition. Senecio inaequidens had higher rates of seedling establishment and a shorter pre-reproductive period. Competition with neighbours had a considerable impact on S. malacitanus, delaying flowering time and reducing growth and reproduction. S. pterophorus showed inefficient seedling establishment compared to the other two species, but performed better in terms of growth and reproduction. The two alien species were markedly more competitive than the native one. However, differences in competitiveness among S. malacitanus and the two aliens varied depending on resource availability. Thus, Senecio inaequidens and S. pterophorus were more affected by competition in subplots with resource addition and by competition in those without addition, respectively. The latter showed a greater capacity to respond to additional resources in competitive environments and, in addition, its reproductive effort was unrelated to habitat conditions. The invasive potential of the alien species was higher than that of the native. This was a result of various biological characteristics and specific interactions between invader and environment, which made the invasiveness of alien species unpredictable.

Geodetic Measurements of Crustal Deformation in the Western Mediterranean and Europe

Geodetic measurements of crustal deformation over large areas deforming at slow rates (< 5 mm/yr over more than 1000 km), such as the Western Mediterranean and Western Europe, are still a challenge because (1) these rates are close to the current resolution of the geodetic techniques, (2) inaccuracies in the reference frame implementation may be on the same order as the tectonic velocities. We present a new velocity field for Western Europe and the Western Mediterranean derived from a rigorous combination of (1) a selection of sites from the ITRF2000 solution, (2) a subset of sites from the European Permanent GPS Network solution, (3) a solution of the French national geodetic permanent GPS network (RGP), and (4) a solution of a permanent GPS network in the western Alps (REGAL). The resulting velocity field describes horizontal crustal motion at 64 sites in Western Europe with an accuracy on the order of 1 mm/yr or better. Its analysis shows that Central Europe behaves rigidly at a 0.4 mm/yr level and can therefore be used to define a stable Europe reference frame. In that reference frame, we find that most of Europe, including areas west of the Rhine graben, the Iberian peninsula, the Ligurian basin and the Corsica-Sardinian block behaves rigidly at a 0.5 mm/yr level. In a second step, we map recently published geodetic results in the reference frame previously defined. Geodetic data confirm a counterclockwise rotation of the Adriatic microplate with respect to stable Europe, that appears to control the strain pattern along its boundaries. Active deformation in the Alps, Apennines, and Dinarides is probably driven by the independent motion of the Adriatic plate rather than by the Africa-Eurasia convergence. The analysis of a global GPS solution and recently published new estimates for the African plate kinematics indicate that the Africa-Eurasia plate motion may be significantly different from the NUVEL1A values. In particular, geodetic solutions show that the convergence rate between Africa and stable Europe may be 30-60% slower than the NUVELIA prediction and rotated 10-30° counterclockwise in the Mediterranean.

OBSIDIAN IN THE MEDITERRANEAN AND THE NEAR EAST: A PROVENANCING SUCCESS STORY

Obsidian provenancing studies comprise one of the most productive and successful research programmes of archaeological science. Obsidian characterization has been successful because workable obsidian is homogeneous on a small scale, analysable by a large number of methods, and is restricted to a small number of mainly readily distinguishable geological sources. Analytical, dating, source, and trade studies within the western Mediterranean, central and eastern Europe, the Aegean, and Anatolia and the Near East during the last 30 years or so are reviewed. Research has shown that distributions are mainly separate in the four regions examined, and that obsidian was traded up to 900km in the prehistoric period. Publications on obsidian in the areas under review reached a peak of frequency in the later 1970s and 1980s, but have now decreased in number. This may reflect changing fashions in archaeometric studies, and a current lack of routine application of the provenancing methods developed.

Use of antagonists to assess PAF receptors heterogeneity

Big storm events represent a major risk for populations and infrastructures settled on coastal lowlands. In the Western Mediterranean, where human societies colonized and occupied the coastal areas since the Ancient times, the variability of storm activity for the past three millennia was investigated with a multi-proxy sedimentological and geochemical study from a lagoonal sequence. Mappings of the geochemistry and magnetic susceptibility of detrital sources in the watershed of the lagoon and from the coastal barriers were undertaken in order to track the terrestrial or coastal/marine origin of sediments deposited into the lagoon. The multi-proxy analysis shows that coarser material, low magnetic susceptibility, and high strontium content characterize the sedimentological signature of the paleostorm levels identified in the lagoonal sequence. A comparison with North Atlantic and Western Mediterranean paleoclimate proxies shows that the phases of high storm activity occurred during cold periods, suggesting a climatically-controlled mechanism for the occurrence of these storm periods. Besides, an in-phase storm activity pattern is found between the Western Mediterranean and Northern Europe. Spectral analyses performed on the Sr content revealed a new 270-year solar-driven pattern of storm cyclicity. For the last 3000 years, this 270-year cycle defines a succession of ten major storm periods (SP) with a mean duration of 96 ± 54 yr. Periods of higher storm activity are recorded from >680 to 560 cal yr BC (SP10, end of the Iron Age Cold Period), from 140 to 820 cal yr AD (SP7 to SP5) with a climax of storminess between 400 and 800 cal yr AD (Dark Ages Cold Period), and from 1230 to >1800 cal yr AD (SP3 to SP1, Little Ice Age). Periods of low storm activity occurred from 560 cal yr BC to 140 cal yr AD (SP9 and SP8, Roman Warm Period) and from 820 to 1230 cal yr AD (SP4, Medieval Warm Period).

A review of palaeobotanical findings of early Vitis in the mediterranean and of the origins of cultivated grape-vines, with special reference to new pointers to prehistoric exploitation in the western mediterranean

The presence in S.E. Spain of Vitis vinifera L. seeds at prehistoric siites of the 3rd millennium B.C., and pollen at Quaternary stations, are considered in the light of conflicting views about the origins of cultivation of the grape and their relation to spontaneous and subspontaneous Vitis in Western Mediterranean Europe. It is proposed that new findings from Spain cast doubt on the widely-held view that Vitis exploitation there is no older than Classical times. Botanical as well as archaeological arguments are put forward to support a greater antiquity of exploitation of Vitis in Mediterranean prehistory, based on a critical review of the literature about both palaeobotanical finds of Vitis and the modern distribution of spontaneous Vitis in the Mediterranean basin and adjacent regions.

BOOK REVIEWS

Abstract Book reviewed in this article: The Open Housing Question: Race and Housing in Chicago, 1966–1976. Brian J. L. Berry. Landscapes of Fear. Yi-Fu Tuun. Grassland Development in the Gran Pajonal of Eastern Peru. Geoffrey A. J. Scott. Western Mediterranean Europe: A Historical Geography of Italy, Spain, and Southern France since the Neolithic. Catherine Deluno Smith Language Aspects of Ethnic Patterns and Processes in the North Caucasus. Ronald Wixman. Transport Network Planning. Patrick O'Sullivan, Gary D. Holtzclaw, and GerLzld M. Barber. Stephen Long and American Frontier Exploration. Roger L. Nichols and Patrick L. Hnlley. Ethnicity on the Great Plains. frederick C. Luebke (Ed.). Migration and Development in South-East Asia: A Demographic Perspective. Robin J. pryor(Ed.). Residential Mobility and Public Policy. W.A.V. Clark and Eric G. Moore(Eds.). Warfare in a Fragile World: Military Impact on the Human Environment. Arthur H. Westing. Human Ecology in Savanna Environments. David R. Harris (Ed.).