Notes on the vegetation of amazonia III. The terminology of amazonian forest types subject to inundation

The types of Amazonian forests subject to inundation can be organized into seven categories which are herewith named and described. This classification is intended to set in order the confusion of terminology used in the past. The types are: (1)seasonal várzea—forest flooded by regular annual cycles of white-water rivers; (2)seasonal igapó—forest flooded by regular annual cycles of black- and clear-water rivers; (3) mangrove—forests flooded twice daily by salt-water tides; (4)tidal várzea—forest flooded twice daily by fresh water backed up from tides; (5)floodplain forest—on low lying ground flooded by irregular rainfall, generally in upper reaches of rivers; (6)permanent white- water swamp forest; (7)permanent igapó—black-water forest. The first five types are periodically inundated and the last two are permanently waterlogged. This terminology is closer to that used by lim nologists by restricting the use ofigapó to forest inundated by black and clear water.     

Dietary cardenolides enhance growth and change the direction of the fecundity‐longevity trade‐off in milkweed bugs (Heteroptera: Lygaeinae)

Sequestration, that is, the accumulation of plant toxins into body tissues for defense, was predicted to incur physiological costs and may require resistance traits different from those of non‐sequestering insects. Alternatively, sequestering species could experience a cost in the absence of toxins due to selection on physiological homeostasis under permanent exposure of sequestered toxins in body tissues. Milkweed bugs (Heteroptera: Lygaeinae) sequester high amounts of plant‐derived cardenolides. Although being potent inhibitors of the ubiquitous animal enzyme Na⁺/K⁺‐ATPase, milkweed bugs can tolerate cardenolides by means of resistant Na⁺/K⁺‐ATPases. Both adaptations, resistance and sequestration, are ancestral traits of the Lygaeinae. Using four milkweed bug species (Heteroptera: Lygaeidae: Lygaeinae) and the related European firebug (Heteroptera: Pyrrhocoridae: Pyrrhocoris apterus) showing different combinations of the traits “cardenolide resistance” and “cardenolide sequestration,” we tested how the two traits affect larval growth upon exposure to dietary cardenolides in an artificial diet system. While cardenolides impaired the growth of P. apterus nymphs neither possessing a resistant Na⁺/K⁺‐ATPase nor sequestering cardenolides, growth was not affected in the non‐sequestering milkweed bug Arocatus longiceps, which possesses a resistant Na⁺/K⁺‐ATPase. Remarkably, cardenolides increased growth in the sequestering dietary specialists Caenocoris nerii and Oncopeltus fasciatus but not in the sequestering dietary generalist Spilostethus pandurus, which all possess a resistant Na⁺/K⁺‐ATPase. We furthermore assessed the effect of dietary cardenolides on additional life history parameters, including developmental speed, longevity of adults, and reproductive success in O. fasciatus. Unexpectedly, nymphs under cardenolide exposure developed substantially faster and lived longer as adults. However, fecundity of adults was reduced when maintained on cardenolide‐containing diet for their entire lifetime but not when adults were transferred to non‐toxic sunflower seeds. We speculate that the resistant Na⁺/K⁺‐ATPase of milkweed bugs is selected for working optimally in a “toxic environment,” that is, when sequestered cardenolides are stored in the body.     

Recent population differentiation in the habitat specialist Glossy Antshrike (Aves: Thamnophilidae) across Amazonian seasonally flooded forests

We assessed population structure and the spatio‐temporal pattern of diversification in the Glossy Antshrike Sakesphorus luctuosus (Aves, Thamnophilidae) to understand the processes shaping the evolutionary history of Amazonian floodplains and address unresolved taxonomic controversies surrounding its species limits. By targeting ultraconserved elements (UCEs) from 32 specimens of S. luctuosus, we identified independent lineages and estimated their differentiation, divergence times, and migration rates. We also estimated current and past demographic histories for each recovered lineage. We found evidence confirming that S. luctuosus consists of a single species, comprising at least four populations, with some highly admixed individuals and overall similar levels of migration between populations. We confirmed the differentiation of the Araguaia River basin population (S. l. araguayae) and gathered circumstantial evidence indicating that the taxon S. hagmanni may represent a highly introgressed population between three distinct phylogroups of S. luctuosus. Divergences between populations occurred during the last 1.2 mya. Signs of population expansions were detected for populations attributed to subspecies S. l. luctuosus, but not for the S. l. araguayae population. Our results support that S. luctuosus has had a complex population history, resulting from a high dependence on southeastern “clear water” seasonally flooded habitats and their availability through time. Spatial and demographic expansions toward the western “white water” flooded forests might be related to recent changes in connectivity and availability of these habitats. Our study reinforces the view that isolation due to absence of suitable habitat has been an important driver of population differentiation within Amazonian flooded forests, but also that differences between várzeas (“white water” floodplains, mostly in southwestern Amazonia) and igapós (“clear water” floodplains, especially located in the east) should be further explored as drivers of micro‐evolution for terrestrial species.     

Response of three arid zone floodplain plant species to inundation

For species to persist on floodplains and in temporary wetlands in arid climates, where large and unpredictable water level fluctuations are common, at least one life history stage must be able to survive inundation. We investigated the survival and performance (RGR, total biomass and above-to-belowground biomass (A:B)) of three common and often coexisting arid zone floodplain species: Xanthium strumarium, Cyperus gymnocaulos and Ludwigia peploides. Observations suggested the species had different responses to inundation, which was tested in a controlled pond experiment. Plants were held at three elevations (+ 10 cm, ? 20 and ? 70 cm) and subjected to three hydrological regimes (static 90 cm, 1 and 5 cm day^?1 inundation) for 16 weeks. Xanthium strumarium died when completely inundated for longer than 4 weeks but when partially flooded survived, showed lower growth rates, increased A:B and produced adventitious roots. C. gymnocaulos showed reduced growth rates when partially flooded and senesced to rhizomes when completely inundated for longer than 4 weeks, which re-sprouted after inundation pressure was removed. L. peploides responded positively to flooding with increased A:B and the production of adventitious roots. The species exhibited three contrasting responses to inundation, which do not necessarily fit neatly within existing water regime functional classification frameworks.     

Physiological control of water exchange in anurans

Research on water exchange in frogs has historically assumed that blood osmotic potential drives water exchange between a frog and its environment, but here we show that the “seat patch” (the primary site of water exchange in many anurans), or other sites of cutaneous water uptake, act as an anatomic “compartment” with a water potential controlled separately from water potential of the blood, and the water potential of that compartment can be the driver of water exchange between the animal and its environment. We studied six frog species (Xenopus laevis, Rana pipiens, R. catesbeiana, Bufo boreas, Pseudacris cadaverina, and P. regilla) differing in ecological relationships to environmental water. We inferred the water potentials of seat patches from water exchanges by frogs in sucrose solutions ranging in water potential from 0 to 1000‐kPa. Terrestrial and arboreal species had seat patch water potentials that were more negative than the water potentials of more aquatic species, and their seat patch water potentials were similar to the water potential of their blood, but the water potentials of venters of the more aquatic species were different from (and less negative than) the water potentials of their blood. These findings indicate that there are physiological mechanisms among frog species that can be used to control water potential at the sites of cutaneous water uptake, and that some frogs may be able to adjust the hydric conductance of their skin when they are absorbing water from very dilute solutions. Largely unexplored mechanisms involving aquaporins are likely responsible for adjustments in hydric conductance, which in turn, allow control of water potential at sites of cutaneous water uptake among species differing in ecological habit and the observed disequilibrium between sites of cutaneous water uptake and blood water potential in more aquatic species.     

Assessing the conservation of Miombo timber species through an integrated index of anthropogenic and climatic threats

AimAngolan Miombo woodlands, rich in timber species of the Leguminosae family, go through one of the highest rates of deforestation in sub‐Saharan Africa. This study presents, on the basis of updated information of the distribution of Leguminosae timber species native to Angola, an integrated index framing the main threats for trees, which aims to support new conservation measures.LocationSub‐Saharan Africa, Republic of Angola.MethodsThe current distribution areas of six Leguminosae timber species (i.e., Afzelia quanzensis, Brachystegia spiciformis, Guibourtia coleosperma, Isoberlinia angolensis, Julbernardia paniculata, and Pterocarpus angolensis) were predicted through ensemble modeling techniques. The level of threat to each species was analyzed, comparing the species potential distribution with a threat index map and with the protected areas. The threat index of anthropogenic and climatic factors encompasses the effects of population density, agriculture, proximity to roads, loss of tree cover, overexploitation, trends in wildfires, and predicted changes in temperature and precipitation.ResultsOur results revealed that about 0.5% of Angola''s area is classified as of “Very high” threat, 23.9% as “High” threat, and 66.5% as “Moderate” threat. Three of the studied species require special conservation efforts, namely B. spiciformis and I. angolensis, which have a large fraction of predicted distribution in areas of high threat, and G. coleosperma since it has a restricted distribution area and is one of the most valuable species in international markets. The priority areas for the conservation of Leguminosae timber species were found in Benguela and Huíla.Main conclusionsThis study provides updated data that should be applied to inform policymakers, contributing to national conservation planning and protection of native flora in Angola. Moreover, it presents a methodological approach for the predictions of species distribution and for the creation of a threat index map that can be applied in other poorly surveyed tropical regions.     

Cytogenetic and Molecular Data Demonstrate that the Bryconinae (Ostariophysi,Bryconidae) Species from Southeastern Brazil Form a Phylogenetic and Phylogeographic Unit

Brycon spp. occur in Neotropical watersheds to the west and east of the Andes, and as they are sensitive to anthropogenic changes, many these species are endangered in southeastern Brazil. Coastal rivers in southeastern Brazil are characterized by the presence of relatively few freshwater fish species and high endemism of this fauna. The objective of this study was to examine whether Brycon spp. occurring in the coastal basins of southeastern Brazil are monophyletic, using cytogenetic data, mitochondrial, and nuclear molecular markers. All the species showed a diploid number of 50 chromosomes, a conserved number within the subfamily Bryconinae. However, the karyotypic formulas were unique to most species, including Brycon devillei (26m+22sm+2st), Brycon ferox (26m+12sm+12st), Brycon insignis (22m+20sm+8st), Brycon opalinus, and Brycon vermelha (24m+20sm+6st), indicating the prevalence of pericentric and paracentric inversions in the chromosomal evolution of these species. All of them had nucleolar organizer regions in the first pair of subtelocentric chromosomes and no equilocal distribution of heterochromatin in the first pair of chromosomes of the karyotype. These two features, not seen in any other Brycon spp. examined to date, indicate that Bryconinae species from the Brazilian southeastern coastal basins, including the monotypic genus Henochilus, are monophyletic. Also, this is the first study that reports NOR location and C-banding patterns as synapomorphies for a Neotropical fish species group. The monophyly was also supported by a phylogenetic analysis of 16S rDNA (16S), cytochrome oxidase subunit I (COI), alpha-myosin (MYH6) genes and S72 intron molecular data. Our results partially corroborate the “Brycon acuminatus” group proposed by Howes in 1982: our proposed clade keeps B. devillei, B. ferox, and B. insignis; but it also includes B. opalinus, B. vermelha, and H. weatlandii whereas it excludes B. nattereri. The phylogeographic unit formed by Bryconinae species in southeastern Brazil reflects the long and isolated paleohydrological history of these coastal basins relative to the continental watersheds.     

DNA Barcodes of Rosy Tetras and Allied Species (Characiformes: Characidae: Hyphessobrycon) from the Brazilian Amazon Basin

DNA barcoding can be an effective tool for fast and accurate species-level identification based on sequencing of the mitochondrial cytochrome c oxidase subunit (COI) gene. The diversity of this fragment can be used to estimate the richness of the respective species. In this study, we explored the use of DNA barcoding in a group of ornamental freshwater fish of the genus Hyphessobrycon. We sequenced the COI from 10 species of Hyphessobrycon belonging to the “Rosy Tetra Clade” collected from the Amazon and Negro River basins and combined our results with published data. The average conspecific and congeneric Kimura 2-parameter distances were 2.3% and 19.3%, respectively. Six of the 10 species were easily distinguishable by DNA barcoding (H. bentosi, H. copelandi, H. eques, H. epicharis, H. pulchrippinis, and H. sweglesi), whereas the remaining species (H. erythrostigma, H. pyrrhonotus, H. rosaceus and H. socolofi) lacked reciprocal monophyly. Although the COI gene was not fully diagnostic, the discovery of distinct evolutionary units in certain Hyphessobrycon species under the same specific epithet as well as haplotype sharing between different species suggest that DNA barcoding is useful for species identification in this speciose genus.     

Nitrogen transformations in microenvironments of river beds and riparian zones

The soil of flooded riparian zones, the rhizosphere of riparian plants, biofilms at solid surfaces in the river, and the surface layer of sediments all constitute important environments for the oxidative or reductive transformations of inorganic nitrogen compounds. The exact microzonation and coupling of the processes have recently been studied intensively with ¹⁵N enrichment methods and microsensors for NH₄⁺, NO₂⁻, NO₃⁻, and N₂O. Microsensor analyses of gradients in sediments and biofilms have shown that nitrate production takes place in an aerobic surface zone that has a maximum thickness of a few millimeters in most shallow-water sediments and may be as thin as 100 μm in biofilms from very eutrophic environments. In the anoxic zone, denitrification is also concentrated in a zone of maximum a few millimeters, and typically half of the nitrate produced by nitrification is denitrified while the other half escapes to the water. The supply of nitrate from above is primarily controlled by the oxic layer acting as a diffusion barrier, and therefore denitrification is generally a linear function of the nitrate concentration in the water. The overlying water is thus a much more important source of nitrate for denitrification if the concentration is high. The rate and location of denitrification are also affected by bioturbating animals, benthic microphytes, plants, and bacteria performing dissimilatory nitrate reduction to ammonium (DNRA).     

Aquatic oligochaete fauna (Annelida,Clitellata) in Lake Tonle Sap and adjacent waters in Cambodia

In surveys conducted during 2000–2005, 39 taxa of aquatic oligochaetes belonging to the families Enchytraeidae and Naididae were found in Lake Tonle Sap in the Mekong River Basin, Cambodia. Dominated by naidines and pristinines (29 taxa), they mainly comprised widely distributed species as well as South Asian and Southeast Asian species. Among the four areas studied, the littoral regions of the lake—where inundated forests and aquatic vegetation developed during the flooded seasons—presented the highest number of species. Submerged vegetation in the littoral Lake Tonle Sap harbored abundant epiphytic oligochaetes, especially Stylaria fossularis. In contrast to the rich abundance of naidine and pristinine fauna, tubificines and ryhacodrilines were scarce in and around the lake, irrespective of the vegetation in their habitats. Several Aulodrilus species and Branchiura sowerbyi were the main representatives of the benthic oligochaete assemblages throughout the offshore zone of the lake without vegetation. It is noteworthy that the widely distributed tubificines Tubifex tubifex and Limnodrilus hoffmeisteri were not found in any surveyed locality.     

Recurring Seasonal Dynamics of Microbial Communities in Stream Habitats

Recurring seasonal patterns of microbial distribution and abundance in three third-order temperate streams within the southeast Pennsylvania Piedmont were observed over 4 years. Populations associated with streambed sediments and rocks (epilithon) were identified using terminal restriction length polymorphism (tRFLP) and sequencing of 16S rRNA genes selectively amplified with primers for the bacterial domain. Analyses of the relative magnitudes of tRFLP peak areas by using nonmetric multidimensional scaling resolved clear seasonal trends in epilithic and sediment populations. Oscillations between two dominant groups of epilithic genotypes, explaining 86% of the seasonal variation in the data set, were correlated with temperature and dissolved organic carbon. Sequences affiliated with epilithic phototrophs (cyanobacteria and diatom chloroplasts), a Rhodoferax sp., and a Bacillus species clustered in the summer, whereas sequences most closely related to “Betaproteobacteria” (putative Burkholderia sp.), and a putative cyanobacterium clustered in the fall/spring. The sediment genotypes also clustered into two groups, and these explained 85% of seasonal variation but correlated only with temperature. A summer tRFLP pattern was characterized by prevalence of “Betaproteobacteria,” “Gammaproteobacteria,” and a Bacillus sp., whereas the winter/spring pattern was characterized by phylotypes most closely related to “Firmicutes,” “Gammaproteobacteria,” and “Nitrospirae.” A close association between these headwater streams and their watersheds was suggested by the recovery of sequences related to microbial populations provisionally attributed to not only freshwaters but also terrestrial habitats.     

Threatened fishes of the world: Brycon nattereri Günther, 1864 (Characidae)

Brycon nattereri (Ostariophysi: Characiformes: Characidae), a threatened South American freshwater fish, occurs in the Paraná, Tocantins and São Francisco river basins in central Brazil. It is a middle-sized (up to 50 cm SL), omnivorous species, which occurs in swift, clear-water rivers with well-preserved riparian vegetation. Main threats to the species are water pollution, dam building, and deforestation.     

Ichthyofauna of the upper Tom’ affected by thermal pollution (West Siberia)

The paper gives comparative analysis of the species composition of fish in the upper Tom’ from the zone of discharge of warm water of electrical power station and background parts of the riverbed. The areas subjected to thermal pollution feature an increase in the number and biomass of introduced species: the share of invaders makes up 19% of the total ichthyomass, 41% of the total number, and 25% of the species diversity of fish. Fish productivity of the mountain taiga part of the upper Tom’ with the increased water temperature exceeds this value of the main riverbed 2–4 times and correlates with the level of productivity of the plain rivers in the south of West Siberia, which is related to eutrophication.     

Extent and role for fish populations of riverine ecotones along the Sinnamary river (French Guiana)

The Sinnamary is a small tropical river (250 km long, watershed of 6500 km²) where a dam is to be impounded in 1994.The extent of naturally periodically flooded areas along the Sinnamary river is estimated by using remote sensing (Landsat TM satellite data) and botanical groupings are described on in situ observations, ground truth and collections. The fish assemblages of these areas are described and their density estimated by rotenone sampling. The role of this ecotone to fish populations is discussed.The extent of the inundated areas appears to be greater than previously estimated by classical mapping.As expected, the fish fauna is mostly composed of fish juveniles and adults of dwarf (< 3 cm) and small (< 15 cm) species. Large predators where not found. Due to these characteristics, fish are abundant but their biomass is low in naturally inundated areas. However, juveniles of some species found only in these zones. Therefore their adult populations will probably be very sensitive to any modification of these land/water ecotones.     

Species diversity and dominance in the planktonic rotifer community of the Pripyat River in the Chernobyl region (1988–1996)

Here, we report the results of monitoring the rotifer community in the Pripyat River within the 30-km evacuation zone of the Chernobyl Nuclear Power Plant over the period 1988–1996. While radionuclide concentration in water did not exceed 4.07 Bq l^–1, the radioactivity in the bottom sediment was quite high, varying irregularly between 113 and 824 kBq m². Radionuclide concentration in the seston also ranged widely: riverbed = 659–2491; backwater = 168–32 832 Bq kg^–1. The rotifer density varied in the range of 65–17 970 individuals l^–1. Sixty-seven rotifer species were identified in the Pripyat, with nine species being previously unknown to this river. Species richness (jackknife estimate) in both the riverbed and the backwater stations was similar and was characterized by a very great variability: riverbed = 66.1 (df=20, SD=39.50); back-water = 66.2 (df=20, SD=42.17). Correlation between the heterogeneity of rotifer community (H ^') and the number of species and relative density of the dominant species was evident. The degree of statistical interrelation between H ^' and relative density of the dominant species was especially high in the riverbed station (r ²= 0.74, p= 0.00001). However, no significant correlation between radionuclide concentration and rotifer biodiversity was found.     

Water use by perennial plants in the transition zone between river oasis and desert in NW China

The study aimed at establishing the role of two possible water sources (inundation, ground water) for the water supply to the perennial plant species Alhagi sparsifolia, Calligonum caput-medusae, Populus euphratica and Tamarix ramosissima growing in the transition zone between a river oasis and the open desert at the southern fringe of the Taklamakan desert (Xinjiang province, NW China). The basic hypothesis was that inundations, which normally occur in summer when rivers from a nearby mountain range carry high water, contribute significantly to the plants’ water supply. When, in the first summer, inundations did not occur, four sites, each of which covered by a relatively dense stand of one species, were artificially flooded. Soil and plant water relations as well as meteorological variables were measured during two growing seasons. Water use efficiency of production (WUE_P) was calculated by relating biomass production, which was determined using allometric regressions, to water use.The effects of artificial flooding on the plant water relations were negligible. Water use was relatively high, especially in the A. sparsifolia and the P. euphratica stands and in a dense stand of T. ramosissima (up to approx. 500 kgH₂O m⁻² year⁻¹). Using the total above-ground biomass in the calculation, WUE_P was highest in C. caput-medusae and P. euphratica, and lowest, in A. sparsifolia. From soil and plant water relations, and against the background of the climate and the productivity of the vegetation, it is concluded that all perennial plants in the transition zone between oases and desert in that region must have sufficient access to ground water to ensure long-term survival. Management of ground water such that it remains continuously accessible to the perennial plants is a prerequisite for the conservation and sustainable use of the vegetation in the transition zone.     

浮游植物群落对海南小水电建设的响应

为探讨浮游植物群落对海南省小水电建设的响应,分别在海南省主要河流的上游支流已建小水电的蓄水水域与河道、规划(未建)小水电河段采集浮游植物样品进行比较分析.共鉴定出浮游植物种类62个属178种,曲壳藻(Achnanthaceae)、异极藻(Gomphonema)、菱形藻(Nitzschia)、颗粒直链藻(Melosira granulat)、席藻(Phormidium)、颤藻(Oscillatoria)、小球藻(Chlorella vulgaris)、平裂藻(Merismopedia)、舟形藻(Navicula)为主要的优势藻类,浮游植物丰度在5.1-163.6×104个/L之间,浮游植物Shannon-Wiener多样性指数在2.73-4.53之间.研究结果表明,小水电建设对浮游植物的种类组成、优势种、丰度及多样性均有较大的影响.就浮游植物优势种而言,规划小水电河道以蓝藻及部分硅藻为主要优势种,已建小水电河道曲壳藻、异极藻、菱形藻等大型硅藻为主要优势种.在浮游植物组成及生物多样性上,未建小水电河道浮游植物Shannon-Wiener多样性指数略高,且种属分布更加均衡,而已建设水电站均趋向某一类藻占主导优势种.就浮游植物丰度而言,规划小水电河道浮游植物丰度均保持在20-30×104个/L内,已建小水电河段浮游植物保持在5-160×104个/L内且浮游植物丰度差异性较规划小水电大,小水电建设促进了浮游植物丰度的提升,但降低了浮游植物群落结构的稳定性、均衡性.虽然存在水电站阻隔,同一河流水系浮游植物种属来源仍可表现一定的趋同性,梯级水电特别是相邻水电间浮游植物群落组成存在较大的相似性.     

Hypoxic coma as a strategy to survive inundation in a salt-marsh inhabiting spider

Spiders constitute a major arthropod group in regularly inundated habitats. Some species survive a flooding period under water. We compared survival during both submersion and a recovery period after submersion, in three stenotopic lycosids: two salt-marsh species Arctosa fulvolineata and Pardosa purbeckensis, and a forest spider Pardosa lugubris. Both activity and survival rates were determined under controlled laboratory conditions by individually surveying 120 females kept submerged in sea water. We found significant differences between the three species, with the two salt-marsh spiders exhibiting higher survival abilities. To our knowledge, this study reports for the first time the existence of a hypoxic coma caused by submersion, which is most pronounced in A. fulvolineata, the salt-marsh spider known to overcome tidal inundation under water. Its ability to fall into that coma can therefore be considered a physiological adaptation to its regularly inundated habitat.     

Phylogenetic Characterization of Two Novel Commensal Bacteria Involved with Innate Immune Homeostasis in Drosophila melanogaster

During a previous study on the molecular interaction between commensal bacteria and host gut immunity, two novel bacterial strains, A911^T and G707^T, were isolated from the gut of Drosophila melanogaster. In this study, these strains were characterized in a polyphasic taxonomic study using phenotypic, genetic, and chemotaxonomic analyses. We show that the strains represent novel species in the family Acetobacteraceae. Strain G707^T, a highly pathogenic organism, represents a new species in the genus Gluconobacter, “Gluconobacter morbifer” sp. nov. (type strain G707 = KCTC 22116^T = JCM 15512^T). Strain A911^T, dominantly present in the normal Drosphila gut community, represents a novel genus and species, designated “Commensalibacter intestini” gen. nov., sp. nov. (type strain A911 = KCTC 22117^T = JCM 15511^T).