Sea Barrier Research Articles

Eastern Asian endemic seed plant genera and their paleogeographic history throughout the Northern Hemisphere

AbstractWe review the fossil history of seed plant genera that are now endemic to eastern Asia. Although the majority of eastern Asian endemic genera have no known fossil record at all, 54 genera, or about 9%, are reliably known from the fossil record. Most of these are woody (with two exceptions), and most are today either broadly East Asian, or more specifically confined to Sino‐Japanese subcategory rather than being endemic to the Sino‐Himalayan area. Of the “eastern Asian endemic” genera so far known from the fossil record, the majority formerly occurred in Europe and/or North America, indicating that eastern Asia served as a late Tertiary or Quaternary refugium for taxa. Hence, many of these genera may have originated in other parts of the Northern Hemisphere and expanded their ranges across continents and former sea barriers when tectonic and climatic conditions allowed, leading to their arrival in eastern Asia. Although clear evidence for paleoendemism is provided by the gymnosperms Amentotaxus, Cathaya, Cephalotaxus, Cunninghamia, Cryptomeria, Glyptostrobus, Ginkgo, Keteleeria, Metasequoia, Nothotsuga, Pseudolarix, Sciadopitys, and Taiwania, and the angiosperms Cercidiphyllum, Choerospondias, Corylopsis, Craigia, Cyclocarya, Davidia, Dipelta, Decaisnea, Diplopanax, Dipteronia, Emmenopterys, Eucommia, Euscaphis, Hemiptelea, Hovenia, Koelreuteria, Paulownia, Phellodendron, Platycarya, Pteroceltis, Rehderodendron, Sargentodoxa, Schizophragma, Sinomenium, Tapiscia, Tetracentron, Toricellia, Trapella, and Trochodendron, we cannot rule out the possibility that neoendemism plays an important role especially for herbaceous taxa in the present‐day flora of Asia, particularly in the Sino‐Himalayan region. In addition to reviewing paleobotanical occurrences from the literature, we document newly recognized fossil occurrences that expand the geographic and stratigraphic ranges previously known for Dipelta, Pteroceltis, and Toricellia.

Spatiotemporal Variation in Fish Assemblage in a Coastal Lagoon without Direct Contact with the Sea (Southeastern Brazil)

Abstract The Cabiunas Lagoon is a narrow water body that is perpendicular to the sea and isolated from it by a sandbank. Before 1991, the sandbank was sometimes opened for a few days by local residents, but at present seawater only enters by limited groundwater seepage or by overtopping the sea barrier in storms. In 1998 the Restinga de Jurubatiba National Park was established, including the Cabiu nas Lagoon. Studies on the structure and spatial distribution of the fish assemblage were performed between 1991 and 1994; we carried out one year (2001–2002) of monthly monitoring of the lagoon to identify spatiotemporal variations in the lagoon fish assemblage. The closed sandbank altered salinity content, and favoured oligohaline conditions and the increase of the aquatic macrophyte abundance, promoting freshwater species dominance and reduction of the marine dependent and some coastal lagoon resident species of fish adapted to paralic ecosystems. Two freshwater, two coastal lagoon resident, and five marine d...

Post-Messinian evolutionary relationships across the Sicilian channel: mitochondrial and nuclear markers link a new green toad from Sicily to African relatives.

BackgroundLittle attention has been paid to the consequences of the last landbridge between Africa and Sicily on Mediterranean biogeography. Previous paleontological and scarce molecular data suggest possible faunal exchange later than the well-documented landbridge in the Messinian (5.3 My); however, a possible African origin of recent terrestrial Sicilian fauna has not been thoroughly tested with molecular methods. To gain insight into the phylogeography of the region, we examine two mitochondrial and two nuclear markers (one is a newly adapted intron marker) in green toads (Bufo viridis subgroup) across that sea barrier, the Strait of Sicily.ResultsExtensive sampling throughout the western Mediterranean and North Africa revealed a deep sister relationship between Sicilian (Bufo siculus n.sp.) and African green toads (B. boulengeri) on the mitochondrial and nuclear level. Divergence times estimated under a Bayesian-coalescence framework (mtDNA control region and 16S rRNA) range from the Middle Pliocene (3.6 My) to Pleistocene (0.16 My) with an average (1.83 to 2.0 My) around the Pliocene/Pleistocene boundary, suggesting possible land connections younger than the Messinian (5.3 My). We describe green toads from Sicily and some surrounding islands as a new endemic species (Bufo siculus). Bufo balearicus occurs on some western Mediterranean islands (Corsica, Sardinia, Mallorca, and Menorca) and the Apennine Peninsula, and is well differentiated on the mitochondrial and nuclear level from B. siculus as well as from B. viridis (Laurenti), whose haplotype group reaches northeastern Italy, north of the Po River. Detection of Calabrian B. balearicus haplotypes in northeastern Sicily suggests recent invasion. Our data agree with paleogeographic and fossil data, which suggest long Plio-Pleistocene isolation of Sicily and episodic Pleistocene faunal exchange across the Strait of Messina. It remains unknown whether both species (B. balearicus, B. siculus) occur in sympatry in northern Sicily.ConclusionOur findings on green toads give the first combined mitochondrial and nuclear sequence evidence for a phylogeographic connection across the Strait of Sicily in terrestrial vertebrates. These relationships may have implications for comparative phylogeographic research on other terrestrial animals co-occurring in North Africa and Sicily.

Calcium carbonate precipitation in cyanobacterial mats from sandy tidal flats of the North Sea

Precipitated calcium carbonate was found in annual cyanobacterial mats developing on the beaches of the North Sea barrier island Schiermonnikoog (the Netherlands). A variety of different calcium carbonate morphs were found in the cyanobacterial mucous secretions and identified by light- and scanning electron microscopy and X-ray diffraction. Most of the calcium carbonate seemed to be associated with degrading extracellular polymer. It is conceived that supersaturation of calcium carbonate resulted from the periodic evaporation of the mats and from the release of calcium from the cyanobacterial mucous as a result of its degradation. The analysis of the carbon stable isotopic composition of the calcium carbonate showed only a slight depletion of (13)C, indicating that it did not in major part originated from the decomposition of organic matter. The delta(18)O values of the calcium carbonate confirmed the temperature differences between spring and summer but excluded the possibility that excessive evaporative events controlled precipitation. The precipitation of calcium carbonate could represent a potential factor enhancing the stabilization of intertidal siliciclastic sediments through cementing the sand. The discovery of massive calcium carbonate precipitation in these cyanobacterial mats was unexpected and hitherto unknown.

Population structure of an island malaria vector

The impact of islands on the population structure of Anopheles flavirostris (Ludlow) (Diptera: Culicidae), the primary malaria vector in the Philippines, was assessed. A phylogenetic analysis of 16 cytochrome oxidase subunit 1 (CO1) haplotypes revealed three clades: one basal clade containing genetically disparate haplotypes from Mindanao, and two derived clades, one of which was largely confined to the largest island, Luzon, and one that was widespread except for Luzon. For the Luzon clade, nested clade analysis revealed an isolation-by-distance effect, and a mismatch distribution analysis diagnosed a recent demographic expansion (sum of squared deviation, SDD = 0.0093, P= 0.075), which mirrors demographic attributes found in mainland primary malaria vectors and could inflate estimates of gene flow from F(ST). For the widespread clade, evidence of range expansion and past fragmentation and/or long distance colonization from the Visayas or Mindanao to Palawan is suggested. A south-to-north range expansion of An. flavirostris is suggested; estimates of coalescence for the Luzon clade was 214 000 years ago (ya) (95% confidence interval 35 600-298 000 ya), i.e. late Pleistocene. Present day rather than Pleistocene island association and some, but not all, sea barriers appeared to be important for An. flavirostris population structure. Our results suggest that endemic island malaria vector species need to be considered before any generalizations are made about the population structure of primary and secondary vectors.

Special Issue on Liquefaction around Marine Structures

In geotechnical-engineering terminology, liquefaction refers to the state of the soil in which the effective stresses between individual soil grains vanish and the water-sediment mixture as a whole therefore acts like a fluid. Under this condition, the soil fails, therefore precipitating failure of the supported structure such as pipelines, breakwaters, seawalls, pile structures, sea barriers, and revetment systems. Although a substantial amount of knowledge has accumulated on flow and scour processes around marine structures in the last decade or so Whitehouse 1998; U.S. Army Corps of Engineers 2001; Sumer and Fredsoe 2002 , comparatively little is known about the impact of liquefaction on these structures. The topic has received little coverage in recent research, which has substantially advanced the design of coastal structures but not the design of their foundations with regard to soil liquefaction. The European Union EU supported a three-year 2001–2004 research program on LIquefaction around Marine Structures LIMAS 2004 http://vb.mek.dtu.dk/research/limas/limas.html . The guest editor, B. Mutlu Sumer, was coordinator of this program. A consortium of 10 European institutions universities, hydraulics and geotechnical-engineering laboratories, and consulting companies undertook this program. The objectives of the program have been twofold: 1 to investigate potential risks for failure of structures caused by liquefaction; and 2 to prepare and disseminate practical guidelines guidance for design and maintenance , to be developed from the present research and also considering all state-of-the-art knowledge. The present volume and a follow-up one are a collection of fifteen papers and a technical note produced from the research undertaken in the LIMAS program. The papers in this volume summarize the results of experimental and theoretical investigations on the fundamental aspects of soil liquefaction around marine structures and focus on processes and benchmark cases. The follow-up volume scheduled for the November issue will include papers on various other aspects of soil liquefaction, including field investigation of momentary liquefaction and scour, momentary liquefaction and gas content, scour around piles in soil with liquefaction history, soil reaction in saturated sand under impulsive loads, development of a sampler for measurement of gas content in soils, and seismic-induced liquefaction around marine structures. The publication of this group of papers will disseminate the results of the LIMAS program worldwide, appealing to end users in consulting companies, contractors, governmental authorities and research entities at universities and research institutions within the coastal and offshore engineering and geotechnical and foundation engineering communities. The publication of this special issue is believed to have broad appeal worldwide and will also build content and create interest in this currently popular area.

A biogeographical analysis of the tenebrionid beetles (Coleoptera, Tenebrionidae) of the island of Thasos in the context of the Aegean Islands (Greece)

This research aimed to study the origin and the biogeographical relationships of the tenebrionid beetle (Coleoptera, Tenebrionidae) fauna of the island of Thasos, with reference to the other Aegean Islands. A total of 32 Aegean Islands and 170 taxa (species and subspecies), 23 of which occur on Thasos, were included in this study. Nine tenebrionid species are here reported for the first time from Thasos, including the first records of Platydema europaeum and Nalassus plebejus from the Aegean Islands. Several models (linear, exponential, power, logistic, Gompertz, Weibull and Lomolino functions) were used to test the species–area relationship. The power function appeared to be the most appropriate model and the parameters of the curve suggest a possible relict character for this fauna. The proportion of Balkan taxa on the islands sharply decreases from west to east, whereas the Anatolian taxa follow an opposite trend. Multi‐dimensional scaling, Parsimony Analysis of Endemicity and discriminant function analysis revealed a clear faunal discontinuity between the western and central Aegean Islands on one side, and the islands close to the Anatolian coast on the other. This discontinuity, consistent with the persistence (from Messinian to Pleistocene) of a sea barrier between these two groups of islands, strongly supports the importance of Pleistocene island configurations in determining present distributional patterns. The comparative richness of the tenebrionid fauna on Thasos is enhanced by the proximity of the island to the mainland and the diversity of its surviving habitats.

The most damaging Indian Ocean tsunami on December 26, 2004

The report summarizes few references dedicated to an initial estimate of the size of the rupture, the amount of energy released, the maximum displacement of the sea bottom and resulting initial water surface profile of tsunami source on December 26, 2004. How the wave train spreads and travels to the land end boundary of the Indian Ocean, and creating huge tsunami bore with so much energy to knock down buildings, trees, human lives, scrapping the land and creating a new landscape. Lesson learnt from remaining buildings, trees, morphologically changed coasts would lead us to the improvement of building code, effective measure of green belt and natural land sea barrier.

Long-tailed Duck, Clangula hyemalis, Eider, Somateria spp., and Scoter, Melanitta spp., Distributions in Central Alaska Beaufort Sea Lagoons, 1999-2002

During July and August 1999–2002, distributions of Long-tailed Ducks (Clangula hyemalis), eiders (Somateria spp.) and scoters (Melanitta spp.) were documented in three barrier island-lagoon systems in the central Alaska Beaufort Sea. Concentration areas for each species were determined during 16 aerial surveys. Kernel density procedures were used to delineate 75% and 50% “activity” or concentration areas for all three species. Long-tailed Ducks were 13 times more numerous than eiders and 38 times more numerous than scoters. The Long-tailed Duck 75% activity area encompassed all three lagoon systems and was three times as large as the eider activity area and one-third larger than the scoter activity area. Eider activity areas were located only in the eastern lagoon, and scoter activity areas were located only in the western lagoon. Density contours showed patterns of repeated habitat use for sea ducks over the four years of sampling and improve our understanding of sea duck habitat use within Beaufort Sea barrier island-lagoon habitats.

Gene flow in great bustard populations across the Strait of Gibraltar as elucidated from excremental PCR and mtDNA sequencing

Recent advances in molecular biology have made it possible to use the trace amounts of DNA in faeces to non-invasively sample endangered species for genetic studies. Here we use faeces as a source of DNA and mtDNA sequence data to elucidate the relationship among Spanish and Moroccan populations of great bustards. 834 bp of combined control region and cytochrome-b mtDNA fragments revealed four variable sites that defined seven closely related haplotypes in 54 individuals. Morocco was fixed for a single mtDNA haplotype that occurs at moderate frequency (28%) in Spain. We could not differentiate among the sampled Spanish populations of Caceres and Andalucia but these combined populations were differentiated from the Moroccan population. Estimates of gene flow (Nm = 0.82)are consistent with extensive observations on the southern Iberian peninsular indicating that few individuals fly across the Strait of Gibraltar. We demonstrate that both this sea barrier and mountain barriers in Spain limit dispersal among adjacent great bustard populations to a similar extent. The Moroccan population is of high ornithological significance as it holds the only population of great bustards in Africa. This population is critically small and genetic and observational data indicate that it is unlikely to be recolonised via immigration from Spain should it be extirpated. In light of the evidence presented here it deserves the maximum level of protection.

Historical biogeography of scarabaeine dung beetles

Abstract Aim (1) To review briefly global biogeographical patterns in dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae), a group whose evolutionary history has been dominated by ecological specialization to vertebrate dung in warmer climates. (2) To develop hypotheses accounting for the evolution of these patterns.Location Six principal biogeographical regions: Palaearctic, Oriental, Afrotropical, Australasia, Neotropical, Nearctic and five outlying islands or island groups harbouring endemic genera: Caribbean, Madagascar, Mauritius, New Caledonia, New Zealand.Methods Major patterns of tribal, generic and species distribution are investigated using cluster analysis, ordination, parsimony analysis of endemism and track analysis. Attempts are made to resolve biogeographical patterns with findings in the fields of plate tectonics, fossil and evolutionary history, plus phylogeny of both mammals and dung beetles.Results Because of conflict between published findings, it is uncertain at what point in time density of dinosaur dung, mammal dung or both became sufficiently great to select for specialized habits in dung beetles. However, biogeographical evidence would suggest a Mesozoic origin followed by further taxonomic radiation during the Cenozoic, possibly in response to the increasing size and diversity of mammalian dung types in South America and Afro‐Eurasia. Proportional generic distribution in fourteen tribes and subtribes showed four principal biogeographical patterns: (1) southerly biased Gondwanaland distribution, (2) Americas or (3) Madagascar endemism, and (4) northerly biased, Afro‐Eurasian‐centred distribution with limited numbers of genera also widespread in other regions. Proportional composition of faunas in eleven geographical regions indicated three principal distributional centres, East Gondwanaland fragments, Afro‐Eurasia and the Americas. These patterns probably result from three principal long‐term range expansion and vicariance events (Mesozoic: Gondwanaland interchange and fragmentation, Cenozoic: Afro‐Eurasian/Nearctic interchange and the Great American interchange). It is suggested that old vicariance caused by the Mesozoic fragmentation of Gondwanaland leads to a high degree of regional endemism at generic or tribal level across one or more Gondwanaland tracks. In contrast, it is suggested that the more recent Cenozoic range expansions occurred primarily towards northern regions leading to endemism primarily at species level. These Cenozoic radiations were facilitated by the re‐linking of continents, either because of tectonic plate movements (Africa to Eurasia in Miocene), climatically induced sea‐level change (Afro‐Eurasia to Nearctic in Miocene and Pleistocene), or similar coupled with orogenics (Nearctic to Neotropical in Pliocene). Speciation has followed vicariance either because of climatic change or physical barrier development. These recent range expansions probably occurred principally along an Afro‐Eurasian land track to the Nearctic and Neotropical and an Americas land track northwards from the Neotropics to the Nearctic, with limited dispersal from Eurasia to Australia, probably across a sea barrier. This accounts for the overall, spatially constrained, biogeographical pattern comprising large numbers of species‐poor genera endemic to a single biogeographical region and fewer more species‐rich genera, many of which show wider biogeographical distributions. In most southerly regions (Australasia, Madagascar, Neotropical), faunal composition and generic endemism is primarily dominated by elements with Gondwanaland ancestry, which is consistent with the Gondwanaland origin claimed for Scarabaeinae. In Afro‐Eurasia (Palaearctic, Oriental, Afrotropical), generic endemism of monophyletically derived Afro‐Eurasian and widespread lineages is centred in the Afrotropical region and faunal composition is numerically dominated by Afro‐Eurasian and widespread elements. In the Nearctic region, the fauna is jointly dominated by widespread elements, derived from Afro‐Eurasia, and Gondwanaland and Americas elements derived from the Neotropical region.Main conclusions Global biogeographical patterns in scarabaeine dung beetles primarily result from Mesozoic and Cenozoic range expansion events followed by vicariance, although recent dispersal to Australia may have occurred across sea barriers. Detailed phylogenetics research is required to provide data to support dispersal/vicariance hypotheses.

Biogeography of the tenebrionid beetles (Coleoptera, Tenebrionidae) on the Aegean Islands (Greece)

AimThis research aimed to study if a transitional character can be postulated for the tenebrionid beetle (Coleoptera, Tenebrionidae) fauna of the Aegean Islands, and to identify ecological and historical factors responsible for observed patterns.LocationEastern Mediterranean, Aegean Islands.MethodsA total of 32 Aegean Islands and 166 taxa (species and subspecies) were included in this study. In order to assess whether the Aegean tenebrionid fauna is mainly equilibrial or relictual, the importance of different eco‐geographical variables (i.e. area, latitude, longitude, distance to the nearest island, distance to the mainland) in determining species richness and endemicity levels was analysed by using several statistical methods. These included single regressions, multiple regressions, and partial correlations. Cluster analysis, multidimensional scaling (MS) and discriminant function analysis (DFA) were used to quantify the similarities between the islands. Regression lines were used to study variations in the proportion of Balkan and Anatolian species. Parsimony Analysis of Endemicity (PAE) was used to study possible relationships between hierarchical species assemblages and palaeogeographical reconstructions.ResultsIsland area accounted for most variability in species number. Distances to the nearest island and to the mainland were not identified as of any statistical importance in affecting species number. The proportion of Balkan taxa sharply decreases from west to east, whereas the Anatolian taxa follow an opposite trend. The proportion of endemic taxa appears uncorrelated with island present isolation, while the proportion of subendemic taxa appears to be affected by present distance to mainland and interisland distances. Cluster analysis, MS and DFA, as well as PAE, revealed a clear faunal discontinuity between the western and central Aegean Islands on one side, and the islands close to the Anatolian coast on the other side. This discontinuity, consistent with the persistence (from Messinian to Pleistocene) of a sea barrier between these two groups of islands, strongly supports the importance of Pleistocene island configurations in determining present distributional patterns.Main conclusionsThe tenebrionid fauna of the Aegean Islands appears to be relictual. Most of the tenebrionid species have probably colonized the Aegean Islands by means of land‐bridges during Pleistocene falls in the sea level. The palaeogeography of Pleistocene island groupings is identified as responsible for present levels of endemicity and distributional patterns. An overall transitional character can be observed for the tenebrionid fauna in the study area. However, in accordance with the persistence of a deep sea barrier between the western and the eastern islands, these two groups appear to harbour very distinct faunas.

Trace metals in suspended particulate matter and sediments from the Severnaya Dvina estuary, Russian Arctic

AbstractA geochemical study of the Severnaya Dvina estuary was carried out during two oceanographic cruises to the White Sea. The amount and distribution of trace (Mn, Co, Cu, Ni, Pb, and Zn) and major (Al and Fe) elements in suspended particulate matter and sediments were determined. The main source of most metals studied was river discharge. A metal speciation study showed that the prevailing form is in the estuarine sediments, the minerals of which incorporated 60–99% of the total metal contents. Two zones of metal accumulation were found in sediments that were considered as local geochemical barriers within the major river–sea barrier.

The Late Quaternary palaeogeography of mammal evolution in the Indonesian Archipelago

The Quaternary faunal evolution for the Indonesian Archipelago reflects the unique relationship of each island with SE Asian mainland. The recent sub faunas of Sundaland (Kalimantan, Sumatra, Java, and Bali) preserved broad connections with the SE Asian mainland during the latest glacial. They are all balanced and show many mainland components. Alternatively, Wallacea (Sulawesi and the Lesser Sunda Islands) has always been geographically isolated from the mainland. Wallacea faunas thus remain unbalanced (they lack large carnivores) and endemic. A significant turnover arrives throughout the region with pronounced global sea level recessions around 0.8 Ma, during the transition from Early Pleistocene (EP) to the Middle Pleistocene (MP). By way of comparison, the palaeontological records of Japan and Taiwan also preserve this turnover, with EP–MP recessions bringing East Asian mainland immigrants. On Java, the earliest, Late Pliocene to early Pleistocene Satir fauna indicates island conditions. Java became connected to the SE Asian mainland towards the end of the early Pleistocene. Global cooling brought open woodlands on Java, an environment evidently preferred by Homo erectus in the Ci Saat fauna and Trinil H.K. fauna. As EP–MP sea level recessions created a wide corridor across the Sunda Shelf, Siwaliks and the SE Asian mainland terrestrial mammals invaded, as is seen in the Kedung Brubus fauna. The succeeding Ngandong fauna maintains an open woodland character but shows some endemism ( Homo erectus and Stegodon trigonocephalus, among others, can be distinguished on a subspecies level). The Late Pleistocene marks the earliest known tropical rainforest, and the corresponding Punung fauna is of Chinese affinity (with Pongo, Hylobates, and Elephas maximus). Homo sapiens probably arrives at this point as well. The youngest fossil faunas known from Java are the still poorly known Cipeundeuy Fauna (ca. 30 ka) and the Holocene faunas from Wajak and Sampung. While Sulawesi and Flores remained isolated throughout the Quaternary, only a limited number of terrestrial vertebrates arrived by crossing sea barriers. Endemic island faunas with pygmy elephantoids and giant tortoises were present during the Early Pleistocene. EP–MP sea level recessions allowed large to medium sized elephantoids to replace the dwarf species. Around the same time, Homo erectus appears on the island of Flores. Modern faunas eventually replaced the Middle Pleistocene island faunas, but the time frame has yet to be pinpointed. Sulawesi presents a unique case. Its current fauna holds no Walanae representatives. Apart from the phalangers, which must have come from the east. The ancestors of all other large Sulawesi land vertebrates, fossil and extant, reached the island by crossing the Sunda Sea. As the South Sulawesi fauna was stable until the Middle Pleistocene, this area must have constituted a separate palaeo-island. Some localized developments can be observed (e.g. shortening of the metapodials in Celebochoerus, increasing hypsodonty in Stegodon).

Alu insertion polymorphisms in NW Africa and the Iberian Peninsula: evidence for a strong genetic boundary through the Gibraltar Straits.

An analysis of 11 I Alu insertion polymorphisms (ACE, TPA25, PV92, APO, FXIIIB, D1, A25, B65, HS2.43, HS3.23, and HS4.65) has been performed in several NW African (Northern, Western, and Southeastern Moroccans, Saharawi; Algerians; Tunisians) and Iberian (Basques, Catalans, and Andalusians) populations. Genetic distances and principal component analyses show a clear differentiation of NW African and Iberian groups of samples, suggesting a strong genetic barrier matching the geographical Mediterranean Sea barrier. The restriction to gene flow may be attributed to the navigational hazards across the Straits, but cultural factors must also have played a role. Some degree of gene flow from sub-Saharan Africa can be detected in the southern part of North Africa and in Saharawi and Southeastern Moroccans, as a result of a continuous gene flow across the Sahara desert that has created a south-north cline of sub-Saharan Africa influence in North Africa. Iberian samples show a substantial degree of homogeneity and fall within the cluster of European-based genetic diversity.

A full sea-level cycle in 65years: barrier dynamics along Caspian shores

The Caspian Sea, being a closed basin, shows much higher rates of sea-level change (up to 340 mm/yr) than the oceans. It experienced a full sea-level cycle with an amplitude of 3 m between 1929 and 1995. Its coasts therefore present an attractive physical model to test predicted changes along oceanic coasts as a result of expected eustatic sea-level rise, and to validate sequence-stratigraphical interpretations of ancient sediments. Along the wave-dominated coasts with intermediate shore-face slopes in Dagestan, low onshore bars were formed during the 1929–1977 sea-level fall. They represent minor short lived (1–2 years) transgressive oscillations within the major regressional trend. After the 1977 lowstand a prominent barrier–lagoon system was formed, which during the first phase of sea-level rise (1977–1988) encroached landwards about 18 m each year by washover during storms (continuous retreat). Between 1988 and 1995, however, barrier size diminished, lagoons widened and deepened, apparently due to lack of coarse-grained sediment supply (discontinuous retreat). The 1995 highstand prevented the barriers from being overstepped altogether. Sea-level fall after 1995 again produced low bars without lagoons. The Caspian Sea barrier coast demonstrates that for the formation of barrier–lagoon complexes the combination of transgression and storms is essential. Barriers may show either continuous or discontinuous development at constant rate of sea-level rise and constant offshore slope, depending essentially on the availability of coarse-grained sediments. The rate of sea-level rise as a factor in barrier behaviour cannot be viewed independently from barrier dimensions, which in turn depend on wave base depth and maximum storm wave height. Relations between (para)sequence thickness, and frequency and amplitude of sea-level change in closed basins with an independent sea-level regime may differ markedly from those in basins influenced by eustasy.

Incongruent phylogeographies in spite of similar morphology, ecology, and distribution:Phippsia algida andP. concinna (Poaceae) in the North Atlantic region

Phylogeographic and taxonomic relationships among 54 North Atlantic populations of the snowbed grass genusPhippsia were investigated based on isozymes and genetically based morphological variation. The results support recognition of two distinct species,P. algida andP. concinna, the latter with at least two subspecies. Both of these self-fertilizing arctic pioneer species were genetic allotetraploids almost without intrapopulational variation. The two species showed strikingly different phylogeographies in the North Atlantic region in spite of their similarity in morphology, habitat ecology, mating system, and dispersal ecology, and in spite of their present cooccurrence in many geographic areas, sometimes even in the same snowbeds. The same electrophoretic multilocus phenotype was observed in all populations ofP. algida, and although this species showed considerable morphological variation, the variation was unstructured geographically. Thus,P. algida showed a pattern similar to other arctic species investigated in the North Atlantic region; it has probably dispersed postglacially across the sea barriers among Greenland, Svalbard, Iceland, and Scandinavia. In contrast,P. concinna was virtually fixed for different multilocus phenotypes in the three main geographic areas analyzed (S Norway, Svalbard, Greenland), corresponding to fairly distinct divergence in morphology. This pattern suggests absence of postglacial among-area dispersal ofP. concinna in spite of all of its similarities with its congener; it may have immigrated to the North Atlantic from different source areas and/or survived the last glaciationin situ.

Regional differences in the morphologic behaviour of four German Wadden Sea barriers

The sandy barriers Japsand, Norderoogsand, Süderoogsand and St. Peter-Ording-Sand are located on the seaward border of the German Wadden Sea. Previous investigations have documented that the barriers Japsand, Norderoogsand and Süderoogsand moved in an eastward direction over a distance ranging from 250 m in the south to 1600 m in the north between 1947 and 1991. It was suggested that this movement by landward rollover occurred in response to a mean 4.9 mm/yr rise of mean high water. In contrast, St. Peter-Ording-Sand which is separated from the other barriers by the Hever tidal inlet seems to persist in the same position. In this study it is demonstrated that this difference in morphologic behaviour is a result of variations in the littoral sediment supply to the four barriers. The morphological development of St. Peter-Ording-Sand between 1949 and 1994 occurred in four phases. During phases I (1949–1964) and III (1981–1988) landward rollover dominated as at the other three barriers. However, during phases II (1964–1981) and IV (1988–1994) the development was dominated by a strong sediment supply to the barrier. As a result, the coastline prograded seaward during these phases. The sediment probably originated from sandbanks that migrated into the area from the Hever tidal inlet.

The Distribution of Schistosoma bovis Sonsino, 1876 in Relation to Intermediate Host Mollusc–Parasite Relationships

Schistosoma bovis is a digenean platyhelminth that is responsible for a parasitic disease called schistosomiasis or bilharziasis in bovines. It has a natural wide mollusc intermediate host spectrum and is compatible, experimentally, with a wide range of species. Our working hypothesis is that the Mediterranean Sea and the Sahara were two physical barriers that could have separated the populations of S. bovis in three parts and may have played a role in gene flow. Experimental data were collected from earlier published studies, and the different intermediate host spectra and the mollusc-parasite geographical compatibilities were compared between the North Mediterranean zone, the South Mediterranean zone and the South Saharan zone. From our results, the three major groups of S. bovis populations that could be determined were the Iberian, the Mediterranean and the South Saharan populations. Our tested hypothesis was thus not confirmed concerning the Mediterranean sea barrier but was confirmed with the Saharan one. A paleogeographical scenario of S. bovis is proposed following three major steps from a South Saharan origin to a possible local adaptation of the parasite in the Iberian Peninsula.

Glacial survival does not matter – II: RAPD phylogeography of Nordic Saxifraga cespitosa

It has been suggested that many arctic‐alpine plant species have limited dispersal ability and cannot have arrived in Scandinavia and the arctic archipelago of Svalbard by long‐distance dispersal after a total glaciation. It has therefore been proposed that such species must have survived the entire glaciation(s) in ice‐free refugia in southern Norway, northern Norway and Svalbard. We investigated random amplified polymorphic DNA (RAPD) variation among 28 populations from Norway and Svalbard of one of these arctic‐alpine ‘short‐distance dispersers’, the selfing polyploid Saxifraga cespitosa. In an analysis of molecular variance (AMOVA), more variation was found among populations within the three postulated refugia regions (45%) than among these regions (25%). Spatial autocorrelation (Mantel) analyses showed that the genetic distance monotonously increased with increasing geographical distance. In UPGMA and PCO analyses, the populations from Norway and Svalbard formed a south–north cline that continued across the Barents Sea barrier. The results suggest that there has been recent dispersal among the three postulated refugia regions and thus that postglacial dispersal into these refugia regions from other distant areas also must represent a possibility. The observed geographical pattern of the genetic variation may have been established after expansion from different source areas outside the North European ice sheet and/or from different refugia areas ‘within’ the ice sheet, but it is probably not possible to distinguish among these alternatives. The results for S. cespitosa are consistent with a dynamic late‐ and postglacial scenario with extensive plant dispersal, and support the conclusion from our previous study of the outbreeding Saxifraga oppositifolia; the hypothesis of glacial survival in Norway and/or Svalbard is superfluous.