Biochemical fingerprints in zooplankton

The use of the role of the species in the habitat (the niche), rather than systematics, for studying the factors that determine which and how many species live in a specific habitat (community assembly), is an approach that has been limited by obvious difficulties in the characterization of the niche. This study shows that is possible to use biochemical fingerprints as indicators of both "requirement niche" and "impact niche" in zooplankton species. Protein content is a good indicator of the nutritive state of the animals and, also, it is a good tool for elucidating food-competitive capacities among species. Reproductive success is positively related with the organic content of the egg (the sum of proteins, carbohydrates, and lipids). Finally, the amino acid composition of the species is a good indicator of the trophic niche and the adaptations of the species to abiotic factors.La utilización del papel de las especies en el hábitat (el nicho), en lugar de la sistemática, para estudiar los factores que determinan cuantas y cuales especies viven en un hábitat (ensamblaje de la comunidad), se ha visto limitado por dificultades obvias a la hora de caracterizar el nicho. Este estudio muestra que es posible usar huellas bioquímicas como indicadores del "nicho de requisitos" y el "nicho de impacto" en especies del zooplancton. El contenido en proteínas es un buen indicador del estado nutritivo de los animales y también es una herramienta útil para dilucidar entre las capacidades competitivas de las especies por el alimento. El éxito reproductivo está relacionado positivamente con el contenido orgánico del huevo (la suma de proteínas, carbohidratos y lípidos). Finalmente, la composición de aminoácidos de las especies es un buen indicador del nicho trófico y de las adaptaciones de las especies a los factores abióticos

Predicting the effects of climate change on future freshwater fish diversity at global scale

The aim of the present study was to predict future changes in biodiversity attributes (richness, rarity, heterogeneity, evenness, functional diversity and taxonomic diversity) of freshwater fish species in river basins around the world, under different climate scenarios. To do this, we use a new methodological approach implemented within the ModestR software (NOO3D) which allows estimating simple species distribution predictions for future climatic scenarios. Data from 16,825 freshwater fish species were used, representing a total of 1,464,232 occurrence records. WorldClim 1.4 variables representing average climate variables for the 1960-1990 period, together with elevation measurements, were used as predictors in these distribution models, as well as in the selection of the most important variables that account for species distribution changes in two scenarios (Representative Concentration Pathways 4.5 and 6.0). The predictions produced suggest the extinction of almost half of current freshwater fish species in the coming decades, with a pronounced decline in tropical regions and a greater extinction likelihood for species with smaller body size and/or limited geographical ranges

Identification of the main factors in structuring rotifer community assemblages in ponds of Doñana National Park using the amino acid composition of the species

The use of the role of the species in the habitat (the niche), as an alternative to systematics for studying the processes that determine which and how many species live in a specific habitat (community assembly), is an approach that has been limited by the difficulties in the characterization of the niche. The aim of this study was to identify the determining factors in rotifers' assemblage in several ponds, using the amino acid composition (AAC) of the species as a fingerprint of the differential niche usage. We found that species with a similar AAC and, hence, with a similar trophic niche, spatially co-exist, showing that trophic-niche differentiation is not a main factor in structuring these lentic associations. The negative relationship between amino acid separation and spatial overlap among rotifer species can be considered as evidence that habitat filtering (abiotic factors) is the factor responsible for the assemblages.La utilización del papel de las especies en el habitat (el nicho), como alternativa a la aproximación sistemática, en el estudio de los procesos que determinan cuales y cuantas especies pueden coexistir en un determinado espacio (ensamble de comunidad), se ha visto limitada por las dificultades que existen para caracterizar el nicho. El objetivo de este estudio es identificar los factores determinantes de la asociación de rotíferos en distintas lagunas, utilizando la composición de aminoácidos (CAA) de las especies como un marcador del distinto uso del nicho. Encontramos que las especies con similar CAA, y por lo tanto, nicho trófico, coexisten espacialmente, lo que demuestra que la diferenciación trófica no es un factor estructurador de estas asociaciones leníticas. La relación negativa entre la separación de aminoácidos y el solapamiento especial entre las especies de rotíferos se puede considerar como una evidencia de que el filtro ambiental (factores abióticos) es el factor responsable de las asociaciones. Los resultados muestran que la salinidad y conductividad son las variables más importantes

Importancia de los fenómenos físicos y la disponibilidad de nutrientes en el control de la concentración de clorofila estimada por satélite en el área costera de afloramiento del Canal de Sicilia

The northern sector of the Sicilian Channel is an area of favourable upwelling winds, which ought to support primary production. However, the values for primary production are low when compared with other Mediterranean areas and very low compared with the most biologically productive regions of the world’s oceans: California, the Canary Islands, Humboldt and Benguela. The aim of this study was to identify the main factors that limit phytoplankton biomass in the Sicilian Channel and modulate its monthly changes. We compared satellite-based estimates of chlorophyll a concentration in the Strait of Sicily with those observed in the four Eastern Boundary Upwelling Systems mentioned above and in other Mediterranean wind-induced coastal upwelling systems (the Alboran Sea, the Gulf of Lions and the Aegean Sea). Our results show that this low level of chlorophyll is mainly due to the low nutrient level in surface and sub-surface waters, independently of wind-induced upwelling intensity. Further, monthly changes in chlorophyll are mainly driven by the mixing of water column and wind-induced and/or circulation-related upwelling processes. Finally, primary production limitation due to the enhanced stratification processes resulting from the general warming trend of Mediterranean waters is not active over most of the coastal upwelling area off the southern Sicilian coast.El sector norte del Canal de Sicilia es un área de vientos favorables para el afloramiento, lo cual debe favorecer la producción primaria. Sin embargo, los valores de producción primaria son bajos comparados con otras áreas del Mediterráneo y muy bajos comparados con las regiones biológicamente más productivas de los océanos a nivel mundial: California, Canarias, Humboldt y Benguela. El objetivo de este estudio fue identificar los principales factores que limitan la biomasa del fitoplancton y modulan sus cambios mensuales. Comparamos estimas de la concentración de clorofila a basadas en satélite en el estrecho de Sicilia, con las observadas en los cuatro sistemas orientales de afloramiento mencionados anteriormente y en otros sistemas costeros del Mediterráneo en los que el viento favorece los afloramientos (Mar del Alborán, Golfo de León y Mar Egeo). Nuestros resultados muestran que la baja producción primaria es debida principalmente a la baja entrada de nutrientes en aguas superficiales, independientemente de la intensidad del afloramiento causado por el viento. Por otro lado, los cambios mensuales en la producción primaria se deben a la mezcla de la columna de agua y afloramientos asociados al viento y/o procesos de circulación en la zona. Finalmente, la limitación de la producción primaria debida al aumento del proceso de estratificación resultante de la tendencia general de calentamiento de las aguas del Mediterráneo, no es activa a lo largo de la mayor parte del área de afloramiento en la costa sur de Sicilia

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.España, Ministerio de Educación y Ciencia CGL2006-02155 BO

Global diversity patterns of freshwater fishes - Potential victims of their own success

Aim To examine the pattern and cumulative curve of descriptions of freshwater fishes world-wide, the geographical biases in the available information on that fauna, the relationship between species richness and geographical rarity of such fishes, as well as to assess the relative contributions of different environmental factors on these variables. Location Global. Methods MODESTR was used to summarize the geographical distribution of freshwater fish species using information available from data-based geographical records. The first-order jackknife richness estimator was used to estimate the completeness of such data in all terrestrial 1-degree cells world-wide. An a-shape procedure was used to build range maps capable of providing relatively accurate species richness and geographical rarity values for each grid cell. We also examined the explanatory capacity of a high number of environmental variables using multiple regressions and Support Vector Machine. Results Cumulative species description curves show that a high number of species of freshwater fishes remain to be discovered. Completeness values indicate that only 199 one-degree grid cells, mainly located in eastern North America and Europe, could be considered as having relatively accurate inventories. Range maps provide species richness values that are positively and significantly related to those resulting from the first-order jackknife richness estimator. The relationship between species richness and geographical rarity is triangular, so that these species-rich cells are those with a higher proportion of distributionally rare species. Species richness is predicted by climatic and/or productivity variables but geographical rarity is not. Main conclusions In general, species-rich tropical areas harbour a higher number of narrowly distributed species although comparatively species-poor subtropical cells may also contain narrowly distributed species. Historical factors may help to explain the faunistic composition of these latter areas; a supposition also supported by the low predictive capacity of climatic and productivity variables on geographical rarity values

A procedure to assess the spatial variability in the importance of abiotic factors affecting distributions: the case of world freshwater fishes

Understanding the factors shaping species' distributions is a key longstanding topic in ecology with unresolved issues. The aims were to test whether the relative contribution of abiotic factors that set the geographical range of freshwater fish species may vary spatially and/or may depend on the geographical extent that is being considered. The relative contribution of factors, to discriminate between the conditions prevailing in the area where the species is present and those existing in the considered extent, was estimated with the instability index included in the R package SPEDInstabR. We used 3 different extent sizes: 1) each river basin where the species is present (local); 2) all river basins where the species is present (regional); and 3) the whole Earth (global). We used a data set of 16,543 freshwater fish species with a total of 845,764 geographical records, together with bioclimatic and topographic variables. Factors associated with temperature and altitude show the highest relative contribution to explain the distribution of freshwater fishes at the smaller considered extent. Altitude and a mix of factors associated with temperature and precipitation were more important when using the regional extent. Factors associated with precipitation show the highest contribution when using the global extent. There was also spatial variability in the importance of factors, both between species and within species and from region to region. Factors associated with precipitation show a clear latitudinal trend of decreasing in importance toward the equator

Predicting the effects of climate change on future freshwater fish diversity at global scale

The aim of the present study was to predict future changes in biodiversity attributes (richness, rarity, heterogeneity, evenness, functional diversity and taxonomic diversity) of freshwater fish species in river basins around the world, under different climate scenarios. To do this, we use a new methodological approach implemented within the ModestR software (NOO3D) which allows estimating simple species distribution predictions for future climatic scenarios. Data from 16,825 freshwater fish species were used, representing a total of 1,464,232 occurrence records. WorldClim 1.4 variables representing average climate variables for the 1960¿1990 period, together with elevation measurements, were used as predictors in these distribution models, as well as in the selection of the most important variables that account for species distribution changes in two scenarios (Representative Concentration Pathways 4.5 and 6.0). The predictions produced suggest the extinction of almost half of current freshwater fish species in the coming decades, with a pronounced decline in tropical regions and a greater extinction likelihood for species with smaller body size and/or limited geographical ranges.We acknowledge institutional support from the Unit of Information Resources for Research at the Unit of Information Resources for Research at the "Consejo Superior de Investigaciones Científicas" (CSIC) for the article-processing charges contribution

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 differencesThis study was supported by the AMAPEZ project (CGL2006-02155 BOS) of the MEC (Ministry of Education and Science) under FEDER funds from the XUNTA de Galicia and by contributions from the Universidad de Vigo, the Universidad de Antioquia, and the Universidad Nacional de Colombia. A. Manjarrés-Hernández gratefully acknowledges a grant from COLCIENCIASS

Testing of the CHEMTAX program in contrasting Neotropical lakes, lagoons, and swamps

ABSTRACT: The problem using the CHEMTAX program in freshwater environments is that the few matrices of pigment ratios available have not been tested in a wide range of environments. Sixteen Amazonian, Andean, and Caribbean lakes, lagoons, and swamps were sampled over a year. The aim was to determine if it was possible to obtain a reliable matrix of input pigment ratios that may be used in freshwater habitats with different environmental conditions. There were no clear differences among regions for most of the ratios of marker pigments to Chlorophyll a (Chl a) in most of the phytoplankton groups. Only the zeaxanthin/Chl a ratio showed clear variations among areas. The estimates for the mean relative contribution of each phytoplankton group calculated for the pigment ratios obtained in each separate habitat and season were very similar to the estimates calculated using the average pigment ratio obtained for all habitats and seasons. Our study suggests that the matrix of the average pigment ratio obtained in this study can be used to estimate phytoplankton class abundances with the CHEMTAX program in freshwater habitats with different limnological conditions