Relative abundances of stratigraphically useful planktonic foraminifers from ODP Leg 167 sites

Late Neogene biostratigraphy of planktonic foraminifers has been investigated from 13 sites cored during Ocean Drilling Program Leg 167 off the coast of California. The planktonic foraminiferal biostratigraphy of six of these sites is presented here at higher stratigraphic resolution for the interval that encompasses the late early Pliocene through the Quaternary (~3.5 Ma to present day). The sites form a transect along the California margin from 31°N to 41°N within the California Current system. A new planktonic foraminiferal zonation has been established largely on evolutionary changes within the Neogloboquadrina plexus, supported by other taxa. A total of eight zones are recognized, most of which are broadly applicable throughout the region, thus providing a biostratigraphic zonation of the sequence at ~0.5-m.y. intervals. The new zonation appears to be unique to the California Current system. The diversity of planktonic foraminiferal assemblages during the late Neogene appears to have remained relatively constant despite large-scale paleoclimatic change. The assemblages are consistently dominated by few taxa that almost always include the neogloboquadrinids and Globigerina bulloides. Low diversity and high dominance of the assemblages favored these and other taxa well adapted to upwelling systems exhibiting high seasonal surface ocean variability. Apparently the oceanographic conditions that favor such assemblages have persisted at least for the duration of the late Neogene (~3.5 Ma to present day). The biostratigraphically important forms have been illustrated with scanning electron micrographs.

Palynological analyses of the sediments around the Miocene/Pliocene boundary in ODP Hole 151-911A

The late Neogene evolution of the Arctic to Subarctic region is poorly understood due to few available records and poor age control. At the margin of the Arctic Ocean, Yermak Plateau Ocean Drilling Program (ODP) Hole 911A is strategically located for establishing a stratigraphic framework for the Arctic. Here we present dinoflagellate cyst and acritarch data from 24 stratigraphic levels in the lower part (474.26-505.64 metres below the seafloor (mbsf)) of ODP Hole 911A. The marine palynomorphs indicate a latest Miocene to earliest Pliocene age (between 5.8 and 5.0 Ma) for the base of the hole based on the co-occurrence of the dinoflagellate cyst Barssidinium evangelineae and acritarch Lavradosphaera crista. Our age estimate for the sediments can possibly be further refined to 5.0-5.33 Ma based on the presence of Achomosphaera andalousiensis suttonensis, which apparently has a range restricted to the Pliocene. An age close to the Miocene/Pliocene boundary agrees with the planktonic foraminifer data. Together with recently available magnetostratigraphic data, the base of the hole is likely to be placed at ~5.2 Ma. This new chronostratigraphy is a first step towards a better understanding of the late Neogene palaeoenvironment for the Yermak Plateau and also for the wider Arctic to Subarctic region. The terrestrial and fresh water palynomorphs were most likely redistributed and/or displaced from the shelf towards deeper parts of the basin during contourite deposition under the influence of the West Spitsbergen Current. The in situ marine dinoflagellate cyst assemblage contains a mixture of cool water and thermophilic taxa, indicating sea-ice free, cool-temperate, warmer than present conditions at the Yermak Plateau. Rivers were likely the source for the freshwater influence.

Pollen record during the Eemian from the Fuentillejo maar-lake sequence (Ciudad Real, Spain)

The Fuentillejo maar is located in the Central Spanish Volcanic Field of Campo de Calatrava (Ciudad Real). Fuentillejo maar-Iake is a c10sed system covering over 142 m depth oflacustrine sediments; it is one ofthe best examples oflong and continuous cores at terrestrial site from the Iberian Peninsula. PalynoIogical, mineralogical and sedimentary facies analysis were performed to characterize the sedimentary record during the Last Interglacial. In core FUENT-l this period (dated in 133 ka-120 ka) is detected between 45,90-56,90 m depth. Sedimentology point of view is characterized by develop of lacustrine facies, fineIy laminated black-brown doIomicrite mud and sapropeIIayers (Sedimentary Units 16,6-17-18). The vegetation is characterised by high polIen taxa diversity (around 50 polIen taxa of terrestriaI types, 5 polIen taxa of aquatic types, spores and 9 types of non palynological microfossils-NPM) together with a high content in the Mediterranean and mesic forest components (Quercus evergreen, Oleaceae, Quercus decidous and CoryIus), tipical ofwarm and humid conditions, and a few content on Artemisia, Pinus and Juniperus taxa (typicaI of coId or warm arid phases). The scarce forest development can be interpreted from the polIen record of mesophilus and thermophilous vegetation of the FUENT-1 sequence, in which only 40-50% of total polIen come from arboreaI associations. These vaIues for arboreal pollen content are low compared with other European polIen sequences.

Molecular evidence for an African origin of the Hawaiian endemic Hesperomannia (Asteraceae)

Identification of the progenitors of plants endemic to oceanic islands often is complicated by extreme morphological divergence between island and continental taxa. This is especially true for the Hawaiian Islands, which are 3,900 km from any continental source. We examine the origin of Hesperomannia, a genus of three species endemic to Hawaii that always have been placed in the tribe Mutisieae of the sunflower family. Phylogenetic analyses of representatives from all tribes in this family using the chloroplast gene ndhF (where ndhF is the ND5 protein of chloroplast NADH dehydrogenase) indicate that Hesperomannia belongs to the tribe Vernonieae. Phylogenetic comparisons within the Vernonieae using sequences of both ndhF and the internal transcribed spacer regions of nuclear ribosomal DNA reveal that Hesperomannia is sister to African species of Vernonia. Long-distance dispersal northeastward from Africa to southeast Asia and across the many Pacific Ocean island chains is the most likely explanation for this unusual biogeographic connection. The 17- to 26-million-year divergence time between African Vernonia and Hesperomannia estimated by the DNA sequences predates the age of the eight existing Hawaiian Islands. These estimates are consistent with an hypothesis that the progenitor of Hesperomannia arrived at one of the low islands of the Hawaiian-Emperor chain between the late Oligocene and mid-Miocene when these islands were above sea level. Subsequent to its arrival the southeast Pacific island chains served as steppingstones for dispersal to the existing Hawaiian Islands.

Distribution of the Ixodes ricinus-like ticks of eastern North America.

We analyzed the geographic distribution of the Ixodes ricinus-like ticks in eastern North America by comparing the mitochondrial 16S rDNA sequences of specimens sampled directly from the field during the 1990s. Two distinct lineages are evident. The southern clade includes ticks from the southeastern and middle-eastern regions of the United States. The range of the northern clade, which appears to have been restricted to the northeastern region until the mid-1900s, now extends throughout the northeastern and middle-eastern regions. These phyletic units correspond to northern and southern taxa that have previously been assigned specific status as Ixodes dammini and Ixodes scapularis, respectively. The expanding range of I. dammini appears to drive the present outbreaks of zoonotic disease in eastern North America that include Lyme disease and human babesiosis.

Late Paleocene to Eocene stable isotope record od ODP Site 143-865

An expanded and largely complete upper Paleocene to upper Eocene section was recovered from the pelagic cap overlying Allison Guyot, Mid-Pacific Mountains at Ocean Drilling Program (ODP) Site 865 (18°26'N, 179°33'W; paleodepth 1300-1500 m). Reconstructions show that the site was within a few degrees of the equator during the Paleogene. Because no other Paleogene sections have been recovered in the Pacific Ocean at such a low latitude, Site 865 provides a unique record of equatorial Pacific paleoceanography. Detailed stable isotopic investigations were conducted on three planktonic foraminiferal taxa (species of Acarinina, Morozovella, and Subbotina). We studied benthic foraminiferal isotopes at much lower resolution on species of Cibicidoides and Lenticulina, Nuttallides truempyi and Gavelinella beccariiformis, because of their exceptional rarity. The d18O and d13C stratigraphies from Site 865 are generally similar to those derived from other Paleocene and Eocene sections. The planktonic foraminiferal records at Site 865, however, include significantly less short-term, single-sample variability than those from higher-latitude sites, indicating that this tropical, oligotrophic location had a comparatively stable water column structure with a deep mixed layer and less seasonal variability. Low-amplitude (0.1-0.8 per mil) oscillations on timescales of 250,000 to 300,000 years correlate between the d13C records of all planktonic taxa and may represent fluctuations in the mixing intensity of surface waters. Peak sea surface temperatures of 24°-25°C occurred in the earliest Eocene, followed by a rapid cooling of 3-6°C in the late early Eocene. Temperatures remained cool and stable through the middle Eocene. In the late Eocene, surface water temperatures decreased further. Vertical temperature gradients decreased dramatically in the late Paleocene and were relatively constant through much of the Eocene but increased markedly in the late Eocene. Intermediate waters warmed through the late Paleocene, reaching a maximum temperature of 10°C in the early Eocene. Cooling in the middle and late Eocene paralleled that of surface waters, with latest Eocene temperatures below 5°C. Extinction patterns of benthic foraminifera in the latest Paleocene were similar to those observed at other Pacific sites and were coeval with a short-term, very rapid negative excursion in d13C values in planktonic and benthic taxa as at other sites. During this excursion, benthic foraminiferal d18O values decreased markedly, indicating warming of 4 to 6°C for tropical intermediate waters, while planktonic taxa show slight warming (1°C) followed by 2°C of cooling. Convergence of d18O values of planktonic and benthic foraminifera suggests that thermal gradients in the water column in this tropical location collapsed during the excursion. These data are consistent with the hypothesis that equatorial Pacific surface waters were a potential source of warm, higher salinity waters which filled portions of the deep ocean in the latest Paleocene. Oxygen isotopic data indicate that equator to high southern latitude sea surface thermal gradients decreased to as little as 4°C at the peak of the excursion, suggesting some fundamental change in global heat transport.

Results of an in situ stable isotope labeling study in intertidal sediment

We report the results of an in situ tracer experiment in an intertidal sediment, where bacterial carbon was tagged with stable carbon-isotope label, after the injection of 13C-glucose. The appearance of label in bacteria (based on label incorporation in bacteria-specific, phospholipid-derived fatty acids) and subsequent transfer to meiobenthos (group level) and macrobenthos (species level) was followed for 36 days. The label dynamics of benthic taxa were either fitted with a simple-isotope model or evaluated against enrichment in bacteria, to derive the importance of bacterially derived carbon for the meiobenthos and macrobenthos. Although selective uptake of bacteria was evident, as 2.4 times more bacterial carbon was grazed as expected from indiscriminate feeding, bacterial carbon accounted on average for only 0.08 and 0.11 of the carbon requirements of meiobenthic and macrobenthic taxa, respectively. Additionally, the contribution of bacterial carbon to total carbon requirements did not depend on the living/feeding depth in the sediment or organism size (evaluated over a size range of four orders of magnitude). The observed overall low contribution of bacterial carbon implies that most intertidal benthic fauna depend primarily on other carbon resources that may assert a stronger control on the structure of intertidal-sediment communities.

Geographic parthenogenesis in the Australian arid zone: I. A climatic analysis of the Heteronotia binoei complex (Gekkonidae)

Patterns of geographic parthenogenesis can provide insight into the ecological implications of the transition from sexual to parthenogenetic reproduction. We analysed quantitatively the environmental niches occupied by sexual and parthenogenetic geckos of the Heteronotia binoei complex in the Australian and zone. This complex consists of two independently derived maternal lineages of hybrid parthenogens, which, in turn, include two different triploid races that resulted from reciprocal backcrossing with the parental sexual taxa. The sexual progenitors are still extant and occupy very distinct environmental niches. The triploid parthenogenetic races are biased in their environmental niche towards those of the sexual races for which their genomes are biased and this dosage effect is apparent in both maternal lineages. Thus triploidy may have benefited the parthenogens through partial recovery of the parental niches. Although the parthenogens have a broader geographic distribution than their sexual progenitors, their environmental niche is narrower and biased towards one of the sexual races. In keeping with general patterns of geographic parthenogenesis. parthenogenetic H. binoei occupy a harsher environment than the sexual forms. occurring in regions of persistently low rainfall. Bioclimatic modelling suggests patterns of rainfall are important in limiting the distribution of sexual and parthenogenetic taxa. and extrapolation from the current bioclimatic profiles indicates potential for further eastward range expansion by the parthenogens.

Ecological persistence interrupted in Caribbean coral reefs [Letter]

The recent mass mortality of Caribbean reef corals dramatically altered reef community structure and begs the question of the past stability and persistence of coral assemblages before human disturbance began. We report within habitat stability in coral community composition in the Pleistocene fossil record of Barbados for at least 95 000 years despite marked variability in global sea level and climate. Results were consistent for surveys of both common and rare taxa. Comparison of Pleistocene and modern community structure shows that Recent human impacts have changed coral community structure in ways not observed in the preceding 220 000 years.

Molecular systematics of the Philippine malaria vector Anopheles flavirostris

Allozyme and molecular sequence data from the malaria vector Anopheles flavirostris (Ludlow) (Diptera: Culicidae) were analysed from 34 sites throughout the Philippines, including the type locality, to test the hypothesis that this taxon is a single panmictic species. A finer-scaled allozyme study, of mainly Luzon samples, revealed no fixed genetic differences in sympatric sites and only low levels of variation. We obtained data from partial sequences for the internal transcribed spacer 2 (ITS2) (483 bp), the third domain (D3) (330 bp) of the 28S ribosomal DNA subunit and cytochrome c oxidase subunit I (COI) of mitochondrial DNA (261 bp). No sequence variation was observed for ITS2, only a one base pair difference was observed between Philippine and Indonesian D3 sequences and An. flavirostris sequences were unique, confirming their diagnostic value for this taxon. Sixteen COI haplotypes were identified, giving 25 parsimony informative sites. Neighbour-Joining, Maximum Parsimony, Maximum Likelihood and Bayesian phylogenetic analysis of COI sequences for An. flavirostris and outgroup taxa revealed strong branch support for the monophyly of An. flavirostris, thus confirming that Philippine populations of this taxon comprise a single separate species within the Minimus Subgroup of the Funestus Group. Variation in the behaviour of An. flavirostris is likely to be intraspecific rather than interspecific in origin. © 2006 The Royal Entomological Society.

PhytoREF: a reference database of the plastidial 16S rRNA gene of photosynthetic eukaryotes with curated taxonomy

Photosynthetic eukaryotes have a critical role as the main producers in most ecosystems of the biosphere. The ongoing environmental metabarcoding revolution opens the perspective for holistic ecosystems biological studies of these organisms, in particular the unicellular microalgae that often lack distinctive morphological characters and have complex life cycles. To interpret environmental sequences, metabarcoding necessarily relies on taxonomically curated databases containing reference sequences of the targeted gene (or barcode) from identified organisms. To date, no such reference framework exists for photosynthetic eukaryotes. In this study, we built the PhytoREF database that contains 6490 plastidial 16S rDNA reference sequences that originate from a large diversity of eukaryotes representing all known major photosynthetic lineages. We compiled 3333 amplicon sequences available from public databases and 879 sequences extracted from plastidial genomes, and generated 411 novel sequences from cultured marine microalgal strains belonging to different eukaryotic lineages. A total of 1867 environmental Sanger 16S rDNA sequences were also included in the database. Stringent quality filtering and a phylogeny-based taxonomic classification were applied for each 16S rDNA sequence. The database mainly focuses on marine microalgae, but sequences from land plants (representing half of the PhytoREF sequences) and freshwater taxa were also included to broaden the applicability of PhytoREF to different aquatic and terrestrial habitats. PhytoREF, accessible via a web interface (http://phytoref.fr), is a new resource in molecular ecology to foster the discovery, assessment and monitoring of the diversity of photosynthetic eukaryotes using high-throughput sequencing.

PhytoREF: a reference database of the plastidial 16S rRNA gene of photosynthetic eukaryotes with curated taxonomy

Photosynthetic eukaryotes have a critical role as the main producers in most ecosystems of the biosphere. The ongoing environmental metabarcoding revolution opens the perspective for holistic ecosystems biological studies of these organisms, in particular the unicellular microalgae that often lack distinctive morphological characters and have complex life cycles. To interpret environmental sequences, metabarcoding necessarily relies on taxonomically curated databases containing reference sequences of the targeted gene (or barcode) from identified organisms. To date, no such reference framework exists for photosynthetic eukaryotes. In this study, we built the PhytoREF database that contains 6490 plastidial 16S rDNA reference sequences that originate from a large diversity of eukaryotes representing all known major photosynthetic lineages. We compiled 3333 amplicon sequences available from public databases and 879 sequences extracted from plastidial genomes, and generated 411 novel sequences from cultured marine microalgal strains belonging to different eukaryotic lineages. A total of 1867 environmental Sanger 16S rDNA sequences were also included in the database. Stringent quality filtering and a phylogeny-based taxonomic classification were applied for each 16S rDNA sequence. The database mainly focuses on marine microalgae, but sequences from land plants (representing half of the PhytoREF sequences) and freshwater taxa were also included to broaden the applicability of PhytoREF to different aquatic and terrestrial habitats. PhytoREF, accessible via a web interface (http://phytoref.fr), is a new resource in molecular ecology to foster the discovery, assessment and monitoring of the diversity of photosynthetic eukaryotes using high-throughput sequencing.

Influência dos obstáculos de pequena dimensão na estruturação dos agrupamentos piscícolas: The impact of small physical obstacles on the structure of freshwater fish assemblages

O efeito das grandes barragens na comunidade piscícola vem sendo documentado por numerosos estudos, enquanto o número de trabalhos que incidem sobre o efeito dos obstáculos de pequena dimensão é bastante mais reduzido. A comunidade piscícola foi amostrada e as variáveis ambientais foram caracterizadas em 28 locais divididos por dois cursos de água da Península Ibérica, 14 dos quais localizados imediatamente a montante, jusante e entre cinco pequenos obstáculos na Ribeira de Muge e 14 na Ribeira de Erra, considerada a linha de água de referência. Através de análise estatística multivariada foi possível verificar que variáveis de habitat como a velocidade de corrente e a profundidade, e não as variáveis físico-químicas, foram as principais responsáveis pela discriminação dos vários grupos de locais nas duas ribeiras. A ribeira de referência exibiu um gradiente longitudinal de velocidade de corrente que, contudo, não era suficientemente forte para causar alterações significativas na composição e estrutura dos agrupamentos piscícolas. Através da sucessiva e drástica repetição deste gradiente junto a cada estrutura, a ribeira com obstáculos apresentou diferenças na fauna piscícola entre os três tipos de locais. Os troços lênticos a montante apresentavam uma densidade mais elevada de espécies limnofilicas, omnívoras e exóticas, como o góbio (Gobio lozanoi), que estão bem adaptadas a este tipo de habitat. Os locais de amostragem situados a jusante e entre os obstáculos caracterizavam-se pela dominância de taxa reófilos e invetivo-os (i.e. barbo, Luciobarbus bocagei). As métricas relacionadas com a riqueza específica não apresentaram diferenças entre os três tipos de locais, ao contrário da diversidade que foi mais elevada nos pontos situados entre os obstáculos, afastados da sua influência directa, onde a diversidade de habitats também é mais elevada. Contrariamente aos locais a montante, os troços a jusante e entre os obstáculos apresentaram similaridades, em muitas das características estudadas, com a ribeira de referência, sugerindo que este tipo de estruturas provoca uma alteração mais significativa na comunidade piscícola a montante. Este estudo sugere que os efeitos dos pequenos obstáculos no habitat e na ictiofauna são, em parte, semelhantes aos descritos para as grandes barragens, fornecendo considerações importantes para os esforços de conservação dos ecossistemas ribeirinhos. ABSTRACT; Many studies have assessed the effects of large dams on fishes but few have examined the effects of small obstacles. Fishes were sampled and environmental variables were characterized at 28 sites in two lberian streams, 14 located immediately downstream, upstream and between five small obstacles at River Muge and 14 at River Erra, considered as the reference stream. Multivariate analysis indicated that habitat variables like current velocity and depth, but not physicochemistry, were the main responsible for site groups' discrimination in both streams. The reference stream exhibited a longitudinal gradient of current velocity that, however, wasn't strong enough to cause significant changes in the fish assemblage's composition and structure. By successive and drastically repeating this gradient near each structure, the obstac1es stream presented differences in fish fauna between the three site types. Lentic upstream sites presented higher density of limnophilic, omnivorous and exotic species, like gudgeon Gobio lozanoi, who are well adapted to this type of habitat. Downstream and between obstacles sites were characterized by the dominance of rheophilic and invertivorous taxa, especially barbel Luciobarbus bocagei. Richness metrics did not differ among site types, but diversity was higher in sites located between the obstacles away from its direct influence, where the habitat diversity was higher. Contrarily to upstream sites, downstream and between obstacles sites were similar in many of the studied features to the reference stream, implying that this type of structures cause a higher modification in the upstream fish community. This study suggests that the effects of small obstacles on habitat and fishes are similar, in some extent, to those reported for larger dams, providing important considerations for riverine ecosystem conservation efforts.