Cástor Guisande

Toxin production and competitive abilities under phosphorus limitation of Alexandrium species

Abstract The relationship between growth rate versus phosphorus concentration and cellular toxin content was determined for Alexandrium minutum AL1V, Alexandrium tamarense MDQ1096, A. tamarense EF04 and Alexandrium andersoni EF12 under different nitrogen and phosphorus supplies. The aim was to determine whether those species with a lower phosphorus uptake affinity, and hence potentially of lower competitive ability at low phosphorus concentrations, were more toxic. The range and mean of toxic content per cell (as fmol per cell) of the species were 13.5–256.5 and 140.2±50.8 for A. tamarense MDQ1096, 0.5–16.5 and 2.9±2.6 for A. minutum, 0–2.0 and 0.2±0.3 for A. tamarense EF04 and, 0–3.3 and 0.06±0.4 for A. andersoni. Ks for culture cell growth (per day),representing the phosphate concentration at which the specific culture cell growth rate is one half the maximum rate, and Kmin (per day), the phosphate concentration at which the specific culture cell growth rate is zero, were used as indicators of species’ potential competitive ability at low phosphorus concentrations. Low values for both Ks and Kmin indicate a high relative ability of the species to use low levels of phosphate and, hence, expected to outcompete higher Ks and Kmin species under phosphorus limitation. Ks and Kmin were 1.68 and 0.48 for A. tamarense MDQ1096, 1.16 and 0.39 for A. minutum, 1.0 and 0.38 for A. tamarense EF04 and, 0.74 and 0.34 for A. andersoni, respectively. There was a significant positive relationship between toxin content per cell with both Ks and Kmin, indicating that those species with lower ability to compete under phosphorus limitation were more toxic. The findings support the hypothesis that toxin production by dinoflagellates species could be an adaptation evolved to offset the ecological disadvantage of having low nutrient affinity.

Comparative responses to metal oxide nanoparticles in marine phytoplankton.

A series of experiments was undertaken on three different marine microalgae to compare the effect of two metal oxide nanoparticles (NPs) on different physiological responses to stress: zinc oxide (ZnO), a known toxic compound for microalgae, and the never before tested yttrium oxide (Y2O3). The effect of these potential pollutants was estimated for different physiological variables and temporal scales: Growth, carbon content, carbon-to-nitrogen (C:N) ratio, and chlorophyll fluorescence were evaluated in long-term assays, and reactive oxygen species (ROS) production was evaluated in a short-term assay. Population growth was the most susceptible variable to the acute toxic effects of both NPs as measured in terms of number of cells and of biomass. Although Phaeodactylum tricornutum and Alexandrium minutum were negatively affected by ZnO NPs, this effect was not detected in Tetraselmis suecica, in which cell growth was significantly decreased by Y2O3 NPs. Biomass per cell was negatively affected in the most toxic treatments in T. suecica but was positively affected in A. minutum. ZnO treatments induced a sharper decrease in chlorophyll fluorescence and higher ROS than did Y2O3 treatments. The pronounced differences observed in the responses between the species and the physiological variables tested highlight the importance of analyzing diverse groups of microalgae and various physiological levels to determine the potential effects of environmental pollutants.

Using modestr to download, import and clean species distribution records

Summary Data quality is one of the highest priorities for species distribution data warehouses, as well as one of the main concerns of data users. There is the need, however, for computational procedures with the facility to automatically or semi-automatically identify and correct errors and to seamlessly integrate expert knowledge and automated processes. New version modestr 2.0 (http://www.ipez.es/ModestR) makes it easy to download occurrence records from the Global Biodiversity Information Facility (GBIF), to import shape files with species range maps such as those available at the website of the International Union for Conservation of Nature (IUCN), to import KML files, to import CSV files with records of the users, to import ESRI ASCII grid probability files generated by distribution modelling software and show the resulting records on a map. modestr supports five different methods for cleaning the data: (i) data filtering when downloading records from GBIF, (ii) habitat data filtering, (iii) taxonomic disambiguation filtering, (iv) automatic spatial dispersion and environmental layer filters and (v) custom data filtering.

Identification of subpopulations in pelagic marine fish species using amino acid composition

The spatial stock complexity of marine fish species requires that population structure is taken into account in fisheries management. The aim of this study was to determine whether the amino acid composition (AAC) of the adult fish allows the identification of subpopulations within the stock. During a cruise in November 2003 along the entire Mediterranean coast of Spain, individuals were collected of the following pelagic species: Sardina pilchardus, Sardinella aurita, Engraulis encrasicolus, Trachurus trachurus, Trachurus mediterraneus, Scomber scombrus and Scomber colias. Individuals of S. pilchardus and E. encrasicolus were also collected from the waters of the Strait of Sicily in 2002 and 2003. The AAC of the fish eyes was seen to be species specific, and therefore, the differences in AAC among species may be based on inherited characters. Moreover, a clear differentiation was seen between the Spanish and Sicilian populations of S. pilchardus and E. encrasicolus. Furthermore, in the Spanish waters of the Mediterranean Sea, discriminant analysis revealed a substantial separation between the northern and southern subpopulations of S. pilchardus, S. aurita and E. encrasicolus. Temporal variations in AAC within species in each area were lower than the spatial variations observed among areas for each species, probably reflecting the influence on the AAC of the contrasting environmental characteristics of each area. Our results indicate that the ACC of the eyes in adult fish is a good tool for discriminating among subpopulations in pelagic marine fish species.

Ecological Factors and Diversification among Neotropical Characiforms

Morphological and DNA sequence data has been used to propose hypotheses of relationships within the Characiformes with minimal comparative discussion of causes underpinning the major intraordinal diversification patterns. We explore potential primary morphological factors controlling the early diversification process in some Neotropical characiforms as the first step to identifying factors contributing to the pronounced intraordinal morphological and species diversity. A phylogenetic reconstruction based on 16S rDNA (mitochondrial) and 18S rDNA (nuclear) genes provided the framework for the identification of the main morphological differences among the Acestrorhynchidae, Anostomidae, Characidae, Ctenoluciidae, Curimatidae, Cynodontidae, Gasteropelecidae, Prochilodontidae and Serrasalmidae. Results indicate an initial split into two major groupings: (i) species with long dorsal-fin bases relative to the size of other fins (Curimatidae, Prochilodontidae, Anostomidae, Serrasalmidae) which primarily inhabit lakes, swamps, and rivers (lineage I); and (ii) species with short dorsal-fin bases (Acestrorhynchidae, Gasteropelecidae, Characidae) which primarily inhabit creeks and streams (lineage II). The second diversification stage in lineage I involved substantial morphological diversification associated with trophic niche differences among the monophyletic families which range from detritivores to large item predators. Nonmonophyly of the Characidae complicated within lineage II analyzes but yielded groupings based on differences in pectoral and anal fin sizes correlated with life style differences.

Effect of bacterial epiflora on egg hatching of the Atlantic sardine (Sardina pilchardus)

The aim of this work was to study the influence of bacterial epiflora on egg hatching of the sardine (Sardina pilchardus) obtained from a natural environment (Ría de Vigo, Spain) during the spawning season of the sardine (from January to June). Total bacteria, viable bacteria or the presence of specific potential pathogens for eggs, such as Pseudoalteromonas piscicida and Tenacibaculum (Flexibacter) ovolyticus, did not affect the viability of sardine eggs. Additionally, no relationship was observed between the presence of Vibrio spp., pathogenic for fish larvae, and the egg hatching. This was probably because the amount of bacteria associated with the eggs were between 10(2) and 10(4) orders lower than those found so far on the eggs of different fish species in rearing systems. Therefore, epiphytic bacteria did not affect the wild sardine eggs and, hence, in the area studied, it is probably not an important factor affecting annual recruitment success of this pelagic fish species.

SPEDInstabR: An algorithm based on a fluctuation index for selecting predictors in species distribution modeling

Abstract Here, we present SPEDInstabR, available as an R package on CRAN and as an RWizard application on http://www.ipez.es/RWizard , which provides tools for the identification of the environmental factors that better discriminate between the conditions prevailing in the area of a species and those existing in the geographical background over which the study is carried out. This could include the world, countries, regions, river basins, etc. or the extent of occurrence of the species estimated by using convex hull, α-shape or Kernel density distributions. The procedure consists of dividing each factor into a number of intervals or bins decided by the user, calculating the number of records in each bin, separately considering the cells where the species occur and those of the selected geographical background. A peak of instability is observed when there are important differences in the factor comparing the bins of presence with the corresponding ones of extent. We consider that those factors with a higher percentage contribution to the Instability index better discriminate between the cells of presence and the extent. We tested the algorithm using virtual species, comparing the generated selections with those produced by MaxEnt.

VARSEDIG: an algorithm for morphometric characters selection and statistical validation in morphological taxonomy

We present and discuss VARSEDIG, an algorithm which identifies the morphometric features that significantly discriminate two taxa and validates the morphological distinctness between them via a Monte-Carlo test. VARSEDIG is freely available as a function of the RWizard application PlotsR (http://www.ipez.es/RWizard) and as R package on CRAN. The variables selected by VARSEDIG with the overlap method were very similar to those selected by logistic regression and discriminant analysis, but overcomes some shortcomings of these methods. VARSEDIG is, therefore, a good alternative by comparison to current classical classification methods for identifying morphometric features that significantly discriminate a taxon and for validating its morphological distinctness from other taxa. As a demonstration of the potential of VARSEDIG for this purpose, we analyze morphological discrimination among some species of the Neotropical freshwater family Characidae.

Geospatial data of freshwater habitats for macroecological studies: an example with freshwater fishes

Global data sets are essential in macroecological studies. File formats of the few available data sets of freshwater ecosystems, however, are either incompatible with most macroecological software packages, incomplete, or of coarse spatial resolutions. We integrated more than 460 million geographical coordinates for freshwater habitats in the FRWater data set, partitioned into seven different habitats (lentic, wetlands, reservoirs, small rivers, large rivers, small ditches, large ditches, small channels, large channels, small drains and large drains) in ModestR (http://www.ipez.es/ModestR). A comprehensive collection of geospatial rasters was assembled, one for each of the seven freshwater habitats, with the area in km2 occupied by each habitat presented in cells of 5 arc-minute resolution. The utility of FRWater was evaluated using hierarchical partitioning via the identification of the contribution of the seven different freshwater habitats to both species richness and rarity. To this end, we used a data set of 836,123 geographical records of the 16,216 species of freshwater fishes recognized as valid by systematists at the end of 2014. Areas in North America and Europe are the most detailed in the FRWater data set, evidencing the higher quality of data sources in those regions. The number of geographical coordinates is much lower for Africa, Asia, Australia, and South America where many water bodies remain unmapped. In light of the variation in information quality at continental levels, we performed and present comparative analyses for Europe versus South America at local (5ʹ × 5ʹ grid cells) and regional (5° × 5° grid cells) scales. The relative contribution of small rivers to both species richness and rarity was highest under almost all analyses, followed by lentic habitats and large rivers. The areas of different habitats moreover explained a relatively high proportion of the observed variance in geographic rarity. Our findings corroborate previous findings that the greater contribution of small rivers to species richness is probably due to these habitats promoting geographical rarity. Hence, species richness is favored by the isolation resultant from, and the refuges associated with, small river basins and via the diversification processes promoted by such isolation.

Amino acid composition reveals functional diversity of zooplankton in tropical lakes related to geography, taxonomy and productivity

Variation in resource use among species determines their potential for competition and co-existence, as well as their impact on ecosystem processes. Planktonic crustaceans consume a range of micro-organisms that vary among habitats and species, but these differences in resource consumption are difficult to characterize due to the small size of the organisms. Consumers acquire amino acids from their diet, and the composition of tissues reflects both the use of different resources and their assimilation in proteins. We examined the amino acid composition of common crustacean zooplankton from 14 tropical lakes in Colombia in three regions (the Amazon floodplain, the eastern range of the Andes, and the Caribbean coast). Amino acid composition varied significantly among taxonomic groups and the three regions. Functional richness in amino acid space was greatest in the Amazon, the most productive region, and tended to be positively related to lake trophic status, suggesting the niche breadth of the community could increase with ecosystem productivity. Functional evenness increased with lake trophic status, indicating that species were more regularly distributed within community-wide niche space in more productive lakes. These results show that zooplankton resource use in tropical lakes varies with both habitat and taxonomy, and that lake productivity may affect community functional diversity and the distribution of species within niche space.