PDF superior Diversity of demersal fish assemblages in the Mediterranean

Diversity of demersal fish assemblages in the Mediterranean

Diversity of demersal fish assemblages in the Mediterranean

lower values in impacted communities, ‘traditional’ diversity indices showed almost null sensitivity. N 90 also showed a response to environmental changes in communities subjected to high levels of fishing pressure, showing the sensitivity of this index to the synergistic effects of climate and fishing. The analysis of MEDITS data between 50 and 800 m depth allowed the identification of a minimum set of indices that provide a good representation of the different aspects of demersal fish diversity in the Balearic Islands. Species richness, evenness and the taxonomic and functional breadth of the species gave complementary information and displayed different responses to fishing pressure. While the impact of fishing on fish communities was detected on the conti- nental shelf, no differences between distinct levels of fishing effort were detected on the slope. That could be due to the demersal fish communities of the middle slope have been subjected to high levels of fishing pressure for a long period, and hence, the vul- nerable species could have been replaced by species better adapted to fishing impacts long time before the onset of the monitoring of the fishery. MEDITS data were also used to analyse the spatial and temporal patterns of demersal fish diversity in the whole northern Mediterranean during the last twenty years. The results showed that the diver- sity of demersal fish assemblages can be explained by the spatial distribution and the temporal trend of the bottom trawl fishing effort in the area. Higher values of diversity were found on the continental shelf of Sicily, the Balearic Islands, Sardinia and Aegean Sea. These last three areas also coincide with low trawl fishing effort values. The con- sideration of species other than target ones through diversity indices is relevant for the implementation of the Ecosystem Approach to Fisheries (EAF). The new developed N 90 diversity index is an alternative to ‘traditional’ diversity indices when trying to monitor fishing impacts and the effects of environmental changes. The easy interpretability of its results can contribute to improve the transfer of scientific knowledge to managers and stakeholders.
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Past and recent demographic histories of western Mediterranean demersal chondrichthyans

Past and recent demographic histories of western Mediterranean demersal chondrichthyans

In the Mediterranean, there is international concern regarding changes in the diversity and abundance of chondrichthyans because of their particular life history traits, which make them vulnerable to fishing impact. However, a lack of accurate landings data on these species and scarcity of biological information have restricted the assessment of their populations. Here, we assess, at community and population levels, the spatio-temporal trends of demersal chondrichthyans in the western Mediterranean, where these species are an important by-catch of bottom trawl fishery. Fishery-independent data were obtained from scientific surveys carried out annually between 1994 and 2015 in the three adjacent geographic sub-areas (GSAs), established by the General Fisheries Commission for the Mediterranean (GFCM) in the western Mediterranean: Northern Alboran (GSA01), Balearic Islands (GSA05) and Northern Spain (GSA06). Our results reflect fairly stable populations in terms of species richness and density (abundance and biomass) levels with some increment in the abundance and biomass of the most abundant species dwelling on the continental shelf (Scyliorhinus canicula, Raja clavata and Torpedo marmorata), and even for the most abundant species dwelling on the slope (Galeus melastomus). In contrast, decreasing trends in some deep water species (Etmopterus spinax and Dipturus oxyrinchus) were observed. These findings can be explained by the reduction of the trawling effort on the continental shelf during the last decades, due to the decreased size of the trawling fleet and to its displacement towards deep waters, along with the higher resilience displayed by some of these species. Meanwhile, while size composition of the most abundant demersal chondrichthyans remained stable over the period analysed, a decreasing trend in length at first maturity of S. canicula was detected, indicating a likely evolutionary response to the general overfishing of demersal resources exploited since 1980s. These results can be useful for implementing management measures that strengthen or initiate the recovery in the Mediterranean of these vulnerable species, whose populations play a very important role in marine ecosystems, in addition to developing true adaptive management.
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Husbandry and environmental conditions explain temporal variability of wild fish assemblages aggregated around a Mediterranean fish farm

Husbandry and environmental conditions explain temporal variability of wild fish assemblages aggregated around a Mediterranean fish farm

Paying special attention to dominant wild fish spe- cies is important since most structural changes can be explained by only these species. Different species exhibit species-specific aggregation patterns, de - pending on their ecology (Bacher et al. 2012). Most studies only associate the presence and/or abun- dance of some fish species with a particular temporal scale (Dempster et al. 2002, Boyra et al. 2004, Valle et al. 2007, Fernandez-Jover et al. 2008, Uglem et al. 2009, Sudirman et al. 2009, Segvi ć Bubi ć et al. 2011, Bacher et al. 2012). Modelling the temporal dynamic of dominant species allows us to predict the distribu- tion of these species around fish farms (Arechavala- Lopez et al. 2010). In our case, GAMs estimated that the maximum abundance of the most dominant spe- cies (B. boops, O. melanura and S. aurita) did not oc - cur at the same time, despite the fact that all 3 species coexist around the farm during warmest seasons and virtually disappear during the colder ones. Also, GAMs showed that the abundance of all 3 species increased profusely around the farm coinciding with their maturation and spawning phases. This kind of reproductive migration towards and away from the farm was postulated by Fernandez-Jover et al. (2008), and can be explained by the optimal foraging para digm (Werner et al. 1983). In our study, the warmer autumn of the second year could be the cause of the slightly delayed maximum abundance of the 3 species during that year. As discussed above, the farm influence could modify the reproductive behaviour of these species.
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TítuloInterannual variability of the diversity and structure
of ichthyoplankton assemblages in the central Mexican Pacific

TítuloInterannual variability of the diversity and structure of ichthyoplankton assemblages in the central Mexican Pacific

The most parsimonious model explaining the assemblage organization includes the ENSO event and seasonality, the second best model only include the ENSO event and the third best model include ENSO, seasonality and the interaction among them (Table 4). The parsimony is rooted in the concept of simplicity and considers only the minimum number of parameters or variables to explain a phenomenon. In this case, the best model only included seasonality and ENSO events to explain the variability of the larval fish assemblages, and posterior increases in the number of parameters in the model could add more complexity than information. The rank of models obtained by the procedure employed can be understood as a hierarchy of the models and implicitly as a hierarchy of environmental factors. The variance decomposition shows the single weight of the variables considered as the environmental variability. Season is the variable that more variance explains followed by ENSO, however season has three possible states (CC, tropical and transition) while ENSO only two (normal and ENSO period) and these is taken in account by the Akaike procedure. The spatial variability, expressed as inshore-offshore gradient is not considered as an important factor in the assemblage organization, and factors as interactions between ENSO and season, showed highest values of explained variance (see table 4).
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Large Scale spatio temporal patterns of mediterranean cephalopod diversity

Large Scale spatio temporal patterns of mediterranean cephalopod diversity

Productivity has often been proposed to influence diversity, and various authors investi- gated this relationship. Our results indicate that low and high Chla seems to enhance species diversity, as the GAM analysis showed a U-shaped effect with positive effect sizes associated with the Aegean and Ionian Sea on one hand and the Iberian-Lions and Adriatic regions (high Chla) on the other hand. This suggests that different mechanisms are in play in different areas, proba- bly because the effect of productivity interacts with other factors and therefore depends on the ecosystem properties. The positive link between Chla content and diversity in productive areas could be due to the fact that sufficient food resources enable less competitive species to survive better than in resource-limited environments, resulting in a higher evenness of the community [7,8]. Furthermore, more productive systems support more species and trophic levels [53]. In fact, a positive relation between net primary production and pelagic cephalopod diversity was found analyzing large-scale patterns worldwide, though this relation was very weak in coastal ecosystems [7,8]. For bacteria, there is experimental evidence showing that seasonal fluctuations in availability of limiting resources can favor biological diversity by the coexistence of different ecotypes via frequency dependent competition [54]. Based on regression analyses, McClatchie et al. [55] found a relationship between demersal fish diversity and surface phytoplankton bio- mass, but they state that this effect may not be causal. A negative effect of Chla, as seen in areas of intermediate Chla content, could be explained by the rise of a few dominant species or changes in food quality (a different phytoplankton community composition having consequences on higher trophic levels) [53]. However, high diversity values observed in the less productive areas of the Mediterranean were likely related to different ecological processes. We argue that high diversity in rather oligotrophic and warm areas, such as the eastern Ionian and the Aegean Sea, may result from closer coupling of the cycles of primary and secondary producers and the low seasonal amplitude of these cycles [7]. These characteristics of oligotrophic regions favor diversity [54,56]. An additional explanation is that the contribution of different species of cephalopods to community diversity in the Eastern Mediterranean is likely different, with higher contribution of species less sensitive to primary production variability and higher sensitivity to other environ- mental variables, for example temperature (Fig 9H) or rainfall [57]. A recent studies in the West- ern Mediterranean shows that, on a given area, two cephalopods species display contrasting responses to a given environmental variable [58].
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Trophic diversity of the otter (Lutra lutra L.) in temperate and Mediterranean freshwater habitats

Trophic diversity of the otter (Lutra lutra L.) in temperate and Mediterranean freshwater habitats

According to the latitudinal gradient in diversity, an increased trophic diversity of the otter in southern latitudes could be related to a higher abundance and availability of non-fish prey in these areas. In fact, at least reptiles and insects are specially abundant in Mediterranean Europe (Blondel & Aronson 1999), where the warm weather conditions allow them to reach large sizes and to be active most of the year. Moreover, the recent spread of the introduced American crayfish (Procambarus clarkii, Girard) has changed the diet of otters and other predators in many Mediterranean habitats (Delibes & Adrián, 1987; Beja, 1996; Correia, 2001), crayfish becoming an important prey. However, a higher availability of alternative prey makes possible, but not forces, an increase of trophic diversity. Besides this, it is usually necessary a reduction in the abundance or availability of the favourite prey (Stephens & Krebs, 1986). Erlinge (1968) stated that captive otters preferred to predate upon fish, and apparently fish are the otter’s staple prey whenever abundant, even under Mediterranean conditions. In fact, otters have an almost exclusive
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Influence of watershed activities on the water quality and fish assemblages of a tropical African
reservoir

Influence of watershed activities on the water quality and fish assemblages of a tropical African reservoir

The various human activities in the water- shed of Oyun reservoir led to increase in the nutrient levels and inadequate fish assemblag- es with the preponderance of some species, absence of other species and decline of commer- cially important species. The human-induced eutrophication which released high amounts of nutrients affected the water quality and species composition and abundance of some species in the reservoir. This is evident in the reduction seen in abundance of commercially important species like Heterotis niloticus and Barbus occi- dentalis as well as in the absence of some other familiar families and species in the reservoir. In order to arrest further degradation of the water quality and inadequate fish assemblages in the reservoir, various watershed activities that put in high amounts of nutrients and sediments into the reservoir should be halted. Good and safe agricultural practices in the watershed will protect the reservoir water quality and improve the fish diversity and abundance. This could be achieved by protecting the reservoir from run-off of agricultural fertilizers and cow dungs from nearby farmlands, educating the end users of the reservoir on the municipal abuse and mis- use of the reservoir and its watershed, as well as in the conservation of the fisheries resources of the reservoir.
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Spatial and temporal variation of fish assemblages in a coastal lagoon of the Biosphere Reserve La Encrucijada, Chiapas, Mexico

Spatial and temporal variation of fish assemblages in a coastal lagoon of the Biosphere Reserve La Encrucijada, Chiapas, Mexico

Low fish diversity values, but high fish abundances (mainly juveniles) are the main characteristics of estuaries and coastal lagoons (Whitfield 1999). There are several factors that may influence the structure of fish assemblages in such systems. Our analyses revealed that salinity and temperature are the major abiotic parameters driving the structure of fish assem- blages in the system Carretas-Pereyra (Fig. 9). This is shown on a temporal basis, where salin- ity changes are noticeable; thus, in the meso- haline regime occurring at the beginning of the dry season (December–January), intermediate abundance, high richness and high species heterogeneity were found. On the other hand, in the polyhaline and oligohaline regimes, both species heterogeneity and species rich- ness were low. In contrast, during the fresh- water regime (October), abundance, richness and Shannon-Wiener’s diversity all attained high values: marine species leave the system and it is invaded by freshwater fishes (e.g., Atractosteus tropicus, Roeboides bouchellei, A. aeneus. P. sphenops, Poeciliopsis fasciata) coexisting with estuarine species (D. latifrons, A. guatemalensis, L. gracilis).
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Multiscale environmental ichthyoplankton assemblages relationships in the balearic sea

Multiscale environmental ichthyoplankton assemblages relationships in the balearic sea

The dispersion of coastal fish larvae from their natal habitat and their subsequent recruitment are prominent issues in the ecology, conservation, and management of fish populations. To understand the underlying mechanisms requires elucidation of the numerous participating biotic and abiotic processes operating at varying spatiotemporal scales. In an ecological context, these scales, despite their broad range, are non-random, as they are modulated by the degree of coupling between ocean dynamics and the speciesspecific biological characteristics of the regional fish populations, such as larval phase duration, larval physiology and behavior, and adult behavior. According to the classical theory, reproductive strategies have evolved such that offspring hatch and develop at times and in areas favorable for their growth and survival (Cushing, 1990). Indeed, larval fish assemblages are the result of convergent spawning strategies by multiple species responding to the same environmental driver. For example, in shelf areas of the Mediterranean Sea, life-cycle strategies often include summer spawning, when oligotrophy prevails in the water column (Antoine et al., 1995; Sabatés et al., 2007) but the probability of dispersal to the open sea by enhanced physical forcing episodes is reduced (Chapter 1, Alvarez et al., 2012). This adaptation to local conditions also allows marine fish populations to maintain a spatial persistence. However, evidence from numerical models and genetic data suggest that, even within a given species, the scale of dispersal in marine organisms can vary widely at different locations in space and time (Cowen et al., 2003; Sotka et al., 2004).
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Biodiversity and structure of parasite communities in Boops boops (Teleostei: Sparidae) from the Western Mediterranean and off the North East Atlantic coasts of Spain.

Biodiversity and structure of parasite communities in Boops boops (Teleostei: Sparidae) from the Western Mediterranean and off the North East Atlantic coasts of Spain.

In contrast to the initial expectations, no impoverishment in the endoparasite fauna of B. boops collected post-spill was observed, since no species from the 2001 samples was missing in the post-spill samples. This suggests no substantial qualitative perturbation of the benthic/pelagic communities or at least the ones associated with B. boops trophic interactions. However, the parasite species lists of the post-spill samples were more than twice as large and included 18 new host records and, of the 19 common species, six were only found in the post-spill samples. Furthermore, a substantially higher richness and abundance of heteroxenous parasites (mostly trematodes) than previously found in the Atlantic B. boops was observed (see also Power et al., 2005 for data covering a wider size range). Overall, the richness and abundance of heteroxenous parasite assemblages exhibited a marked peak in communities of the pilot study and were notably higher in all post-spill samples, although some tendency of a decrease in abundance was noted after spring 2005. The hemiuroids, mostly represented by generalist parasites that are shared with many marine fish species (see Gibson & Bray, 1986 and NHM Host-parasite database, www.nhm.ac.uk/research-curation/projects/host-parasites/database), comprised up to 90% of the heteroxenous parasites in the post-spill samples and strongly contributed to the observed patterns of richness and abundance. These observations largely depart from the initial hypothesis that the two model groups of parasites selected for a comparative study would exhibit an opposing response to the post-spill situation. Whereas the presence of the tissue heteroxenous parasites in the post-spill samples (the metacercariae of Stephanostomum spp. and Prosorhynchus sp., C. longicollis, unidentified renicolid; the post-cystacanths of Corynosoma sp. and Andracantha spp.; and larval anisakids) might be related to the inmunosupression of the fish, no published evidence could be found for a positive effect of PAHs (or other xenobiotics) on trematode populations in their final hosts. Previous work, on the contrary, suggests that pollution (including oil and heavy metals) is toxic to adult trematodes in the fish hosts (e.g. Overstreet & Howse, 1977; Khan & Kiceniuk, 1983; Overstreet, 1988; Khan & Thulin, 1991) and lethal to free-living stages as well as to mollusc intermediate hosts, thus compromising the transmission of the heteroxenous species by blocking the completion of their life-cycles (Dzikowski et al., 2003 and references therein; but see Powell et al., 1999) .
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Seasonal variation in the diversity and composition of phyllostomid bat assemblages in continuous and fragmented forests in Los Chimalapas, Oaxaca, Mexico

Seasonal variation in the diversity and composition of phyllostomid bat assemblages in continuous and fragmented forests in Los Chimalapas, Oaxaca, Mexico

Palabras clave: selva tropical, Phyllostomidae, fragmentación de hábitat, gremios tróficos, variabilidad temporal. Abstract. The fragmentation of tropical forest may modify the abundance and species richness of bats, but its effects on the temporal composition of assemblages have been less understood. We evaluate the species richness, diversity, proportion of trophic guilds, and composition of nose-leaf bat assemblages in continuous (BC) and fragmented (BF) forest, during 2 dry and 2 rainy seasons in a forest of Los Chimalapas, Oaxaca, Mexico. In this study we conducted from March 2010 to February 2012, and bats were captured with mist nets during 144 nights. We captured 1 840 individuals of 29 species of nose-leaf bats. The results show that BC has a temporal pattern of richness, dominance, diversity, and proportion of trophic guild according to variations in food availability in each season. The BF show little temporal variability in the above features, but high variability in the composition of assemblages compared to BC, that show more stability. Habitat fragmentation may intensify the severity of seasonal changes in the availability of resources, which in turn may cause a greater temporal variability in the composition of assemblages.
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First record of the epizoic red seaweed Polysiphonia carettia Hollenberg in the Mediterranean Sea.

First record of the epizoic red seaweed Polysiphonia carettia Hollenberg in the Mediterranean Sea.

algae growing on loggerhead turtles of the western Mediterranean Sea, in order to distinguish the Atlantic from the eastern Mediterranean populations of loggerhead turtles.. carettia [r]

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Marine macrophytes and the Water Framework Directive: preliminary studies in southern Spain

Marine macrophytes and the Water Framework Directive: preliminary studies in southern Spain

There have been relatively few attempts to determine the biological quality of Atlantic transitional waters using macroalgae as BQEs (e.g. Borja et al. 2004). There are methods proposed in the UK and Portugal based on opportunistic macroalgal blooms (Scanlan et al. 2007, Patricio et al. 2007, WFD-UKTAG 2009) and above all, the extent of upstream penetration of perennial fucoid algae (Wilkinson et al. 2007). The methods based on opportunistic algae may be difficult to apply, as coverage or algal density of opportunistic Ulvaceans is highly variable both spatially and seasonally among estuaries (Hernández et al. 1997). In addition, in some cases, opportunistic algal cover responds to environmental variables not necessarily related to pollution, as water clarity and salinity (Krause- Jensen et al. 2007). These methods could be used during peak bloom periods but still needs an assessment in Andalusian transitional waters. The method based on fucoids cannot be applied in the Spanish south Atlantic estuaries as there are few records of fucoids in transitional waters.
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Conservation planning of vertebrate diversity in a Mediterranean agricultural dominant landscape

Conservation planning of vertebrate diversity in a Mediterranean agricultural dominant landscape

conservation areas (Natura 2000 Network and current natural protected areas), and connectivity 769.. (b) Higher magnification of the boxed area in (a) that illustrates least- 770[r]

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Latitudinal diversity patterns of chilean coastal fishes: searching for causal processes

Latitudinal diversity patterns of chilean coastal fishes: searching for causal processes

These peaks of intertidal fish species richness at tem- perate latitudes, where richness can apparently vary without a particular trend at intermediate latitudes, could be widespread in fish living in these environ- ments. Prochazka et al. (1999) collected bibliographic in- formation on intertidal fish from different temperate and tropical regions of the world, and despite the possible bias and lack of representation associated with such di- verse bibliography, there is still no clear indication of a decrease in richness with increasing latitude, at least not at intermediate latitudes. This particular pattern may be the result of underlying processes related to the particu- lar and highly variable conditions of the intertidal envir- onment, specifically tide pools. In this environment, the observed pattern emerges from the specific characteris- tics of the resident fish fauna, whose species are usually small and cryptic in habit and coloration. These charac- teristics are generally considered to be specialized to intertidal life (Horn et al. 1999). Similarly, other marine
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Chrysichthys nigrodigitatus has experien- ced extreme proliferation during the period becoming the most important species in terms of weight although it was not observed in the area before impoundment. Though it is not clear what might have caused the proliferation in C. nigrodigitatus, it could be enhanced by biological and environmental factors. Similarly Barbus macrops has increased its relative abun- dance in the Kpong reservoir almost ten times similar to what pertained in the Weija Reservoir after 28 years of impoundment (Quarcoopome & Amevenku 2006). This was partly attributed to the fishing pressure due to specialization of capture exerted on the larger-sized and more preferred fish species which then encouraged the proliferation of Barbus macrops and Bry- cinus leuciscus. Singit et. al. (1988) reported similar occurrences in Indian reservoirs.
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TítuloEditorial statement: The first two years of EJGE

TítuloEditorial statement: The first two years of EJGE

One year has passed since our last editorial, in which we discussed our efforts to include the journal in some indices in order to improve its visibility and impact. We also discussed the geographical base of the journal, as well as our intention to make it accessible to a broader economic and political science audience by avoiding unnecessary technical oversophistication (Varela et al., 2012a). In the current year, we have continued our work along the lines of expanding the journal base, both geographically and methodologically, and working for inclusion by abstracting and indexing services. We have also harvested our first fruits in terms of academic impact measured by citations received by our papers in other major publications.
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Assessment of PM10 and heavy metal concentration in a ceramic cluster (NE Spain) and the influence on nearby soils

Assessment of PM10 and heavy metal concentration in a ceramic cluster (NE Spain) and the influence on nearby soils

VICENTE,  A.  B.,  et  al.  Assessment  of  PM10  and   heavy  metal  concentration  in  a  ceramic  cluster   (NE  Spain)  and  the  influence  on  nearby  soils.   Journal  of  Geochemical  Exploration,  2014,  144:   320-­‐327  

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Orígenes globales de la primera guerra mundial. Parte dos: Una cadena de eventos revolucionarios en todo el mundo Isla

Orígenes globales de la primera guerra mundial. Parte dos: Una cadena de eventos revolucionarios en todo el mundo Isla

Grey decided to send Lord Haldane, the War Minister to get an Anglo-German agreement on what would in the Cold War be called arms control, that is, not arms reduction, but a regulation of the pace of arms building. Haldane was, he said, prepared to consider German ambitions outside Europe. Big business and high finance, whom some critics on the left saw as pulling the strings behind a race toward war, instead weighed in on the side of détente. For the Germans, Albert Ballin of the Hamburg America steamship line, and for the British, the financial magnate Sir Ernest Cassel, both did their best to use their connections to promote an agreement. In the abstract, the naval issues seemed amenable to compromise. The Germans had a naval bill pending, the novelle, to use as a bargaining chip. Even so, they were willing to compromise on the precise ratio of British supremacy. But the agreement foundered on “linkage,” the price that the British were expected to pay in Africa or elsewhere for German recognition of the permanence of British superiority on the seas. Hitler thought he had put the British in such a position in 1935, when he traded recognition of British naval supremacy for what he thought was a free hand in Eastern Europe. The Kaiser fully expected to get what he crudely called “a large chunk of colonial territory”. Haldane found that embarrassing and difficult to sell at home. Domestic pressures also loomed on the other side. The German Social Democrats had emerged in the elections of 1912 as the biggest party in the Reichstag. Ironically this worked for greater tensions. Tirpitz had long advertised the
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El Andaluciense como unidad cronoestratigráfica adecuada para el área mediterránea

El Andaluciense como unidad cronoestratigráfica adecuada para el área mediterránea

2 ) Supposed «Atlantic» ¡eatures of the Andalusian.. a ) Occurrence in the terminal Miocene of Carmona of Globoquadrina altispiru, species thai disappear in the Mediterranean, in the Se[r]

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