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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.
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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.
Assuntos
Lagos , Zooplâncton , Aminoácidos , Animais , Região do Caribe , Ecossistema , GeografiaRESUMO
ResumenLa morfología funcional corresponde a las respuestas de adaptación a los cambios en el medio ambiente. En fitoplancton, rasgos como el desarrollo de mucílago, vesículas de aceite, filamentos y variación en la relación superficie/ volumen, permiten enfrentar la sedimentación, optimizar la captación lumínica y de nutrientes. El objetivo del presente estudio fue evaluar la relación entre los rasgos y la variación de las condiciones físicas y químicas en el lago de Tota (Boyacá, Colombia). Para esto, se realizaron diez muestreos mensuales entre octubre 2013 y julio 2014. Se midieron el pH, conductividad eléctrica, temperatura, oxígeno disuelto, saturación de oxígeno, alcalinidad y dureza total del agua. Además se recolectaron muestras para la cuantificación en laboratorio de Nitrógeno Total Kjeldahl y Fósforo Total. Las algas se obtuvieron en diferentes profundidades según la transparencia Secchi. Se caracterizó la composición taxonómica y se estimó la abundancia por el método de sedimentación en cámaras. Se midieron los rasgos morfológicos de cada taxa según la correspondencia a modelos geométricos, se clasificaron en grupos funcionales basados en morfología (GFBM) y se calculó su biomasa expresada como biovolumen. Las variables fueron evaluadas mediante Análisis de Componentes Principales, que incluyó el efecto espacio-temporal y fue interpretado según la variación en el nivel del agua. Mediante Análisis de Correspondencia Canónica se estableció la relación entre el biovolumen del fitoplancton acumulado en categorías de forma y las variables ambientales. La ordenación mostró que las condiciones limnológicas son influenciadas por cambios estacionales, principalmente representadas por el porcentaje de saturación de oxígeno, la transparencia Secchi, el NTK, la dureza y la alcalinidad. Se encontraron cuatro GFBM: IV, V, VI y VII, siendo los GFBM IV y VII, los más representativos. El ACC fue significativo (Test de Monte-Carlo, p<0.05). En conclusión, la respuesta morfológica y funcional del fitoplancton del lago de Tota esta condicionada principalmente por la variabilidad a corto plazo, en la transparencia, el fósforo, el nitrógeno, la dureza y la conductividad eléctrica, que son afectados por los cambios estacionales en el nivel del lago.
AbstractFunctional morphology corresponds to adaptive responses to changes in the environment. In phytoplankton, traits such as the development of mucilage, oil vesicles, filaments and variation in the surface/volume ratio, allow algae to deal with sedimentation, optimizing light and nutrient uptake. The aim of this research was to evaluate the relationship between traits and variation in physical and chemical conditions in Tota Lake (Boyacá, Colombia). For this, ten samplings were undertaken in a monthly basis between October 2013 and July 2014. We measured water pH, conductivity, temperature, dissolved oxygen, oxygen saturation, alkalinity and total hardness; we also quantified Total Kjeldahl nitrogen and Total phosphorus. Algae were collected at different depths according to Secchi transparency. Taxonomic composition and abundance were estimated by the chamber sedimentation method. Morphological traits were measured for each taxa according to geometric models, allowing traits classification into morphologically based functional groups (MBFG) and having algae biomass expressed as biovolume. The variables were evaluated through Principal Components Analysis, which included time-space effect and it was interpreted according to variation in water level. Through Canonical Correspondence Analysis we established the relationship between phytoplankton biovolume accumulated in form categories and environmental variables. The ordination showed that limnological conditions are influenced by seasonal changes, which are mainly represented by oxygen saturation percentage, Secchi transparency, TKN, hardness and alkalinity. Four MBFG were found: IV, V, VI and VII, being MBFG IV and VII the most representatives. ACC was significant (Monte-Carlo Test, p<0.05). In conclusion, the morphological and functional response of phytoplankton in Tota Lake is driven by short-term variability in transparency, phosphorus, nitrogen, hardness, and electrical conductivity, which are all affected by seasonal changes in the lake level.
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The objective of this study was to identify and describe the nesting habitat of Podocnemis sextuberculata at Erepecu Lake, Trombetas River Biological Reserve, (REBIO-Trombetas; Pará-Brazil). Initially, the main features of the beaches that potentially determine the habitat selection by cupiso for nesting were described. The nests observed on the beaches were recorded, marked and fenced as protection from natural predators. Information regarding date and location was analyzed through simple linear regression for each nest in order to determine relationships between beach features and number of nests. The results showed a positive co-relationship between number of nests and area. Nest site selection by P. sextuberculata in the beaches of the Erepecu Lake could depend on trade-off scenarios among natural threats and a suitable nesting habitat. We also suggest that, due to the high annual hydrologic oscillations, it is possible that the driving factor for habitat selection would be the risks that the females are exposed to while searching for a nesting site, rather than a particular habitat type.
El objetivo del estudio fue identificar y explicar la influencia del hábitat sobre los nidos de la tortuga "cupiso" (Podocnemis sextuberculata), en el lago Erepecu ubicado en la Reserva Biológica del Río Trombetas (REBIO-Trombetas; Pará-Brasil). Inicialmente se describieron las principales características de las playas escogidas, los nidos encontrados fueron marcados y cercados para su protección contra la depredación natural. A través de regresiones lineales simples se determinó que el número de nidos por playa se correlacionó significativamente con el "área" de las playas. Los resultados muestran que la selección del lugar de nidificación en las playas del lago Erepecu por P. sextuberculata, podría depender en unos escenarios de compensación entre las amenazas naturales y un hábitat adecuado para anidar. Debido a la gran fluctuación hidrológica anual, es posible que el factor determinante para selección de las hembras sea el riesgo de exposición de las hembras durante la búsqueda de área de anidación, más que el tipo de hábitat en particular.
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The diatom flora of the Colombian and Peruvian Amazon is far less studied than the flora of the Brazilian sector of the basin. Here we present results related to the genera Encyonema, Encyonopsis and Gomphonema. Plankton and periphyton samples were collected in lotic and lentic waterbodies from the Amazonian-Andean region, the Amazon River, Japurá River and Porvenir River basins during 1993, 1994, 2001 and 2003. At each sampling station pH, temperature, water transparency and conductivity were registered. Samples were analyzed with phase contrast microscope (LM) and scanning electron microscope (SEM). Ten taxa are new records for the area; Encyonema for the Peruvian and Colombian Amazon and Encyonopsis for the Colombian Sector. Encyonema neogracile var. tenuipunctatum, E. vulgare, Encyonopsis frequentis, Gomphonema augur var. sphaerophorum and G. contraturris are recorded for the first time in Colombia; Encyonema venezolanum and G. neoapiculatum in Colombia and Peru and the latter also for Amazonia. E. angustecapitatum was mentioned in Colombia before at a pond located at 3000 m asl. We describe a new species from Porvenir River, Amazonas, Colombia: Encyonema amazonianum.
Assuntos
Diatomáceas/classificação , Colômbia , Diatomáceas/ultraestrutura , Microscopia Eletrônica de Varredura , Peru , RiosRESUMO
Diatoms from the Colombian and Peruvian Amazon: the Genera Encyonema, Encyonopsis and Gomphonema (Cymbellales, Bacillariophyceae). The diatom flora of the Colombian and Peruvian Amazon is far less studied than the flora of the Brazilian sector of the basin. Here we present results related to the genera Encyonema, Encyonopsis and Gomphonema. Plankton and periphyton samples were collected in lotic and lentic waterbodies from the Amazonian-Andean region, the Amazon River, Japurá River and Porvenir River basins during 1993, 1994, 2001 and 2003. At each sampling station pH, temperature, water transparency and conductivity were registered. Samples were analyzed with phase contrast microscope (LM) and scanning electron microscope (SEM). Ten taxa are new records for the area; Encyonema for the Peruvian and Colombian Amazon and Encyonopsis for the Colombian Sector. Encyonema neogracile var. tenuipunctatum, E. vulgare, Encyonopsis frequentis, Gomphonema augur var. sphaerophorum and G. contraturris are recorded for the first time in Colombia; Encyonema venezolanum and G. neoapiculatum in Colombia and Peru and the latter also for Amazonia. E. angustecapitatum was mentioned in Colombia before at a pond located at 3000m asl. We describe a new species from Porvenir River, Amazonas, Colombia: Encyonema amazonianum. Rev. Biol. Trop. 58 (1): 45-62. Epub 2010 March 01.
La flora diatomológica de la Amazonia Colombiana y Peruana está mucho menos estudiada que la flora del sector brasilero. Se presentan los resultados de los géneros Encyonema, Encyonopsis y Gomphonema. Muestras de plancton y perifiton fueron colectadas en ambientes lóticos y lénticos de la región amazónica-andina, en los ríos Amazonas, Japurá y Porvenir durante 1993, 1994, 2001 y 2003. En cada estación de muestreo se realizaron mediciones de pH, temperatura, transparencia del agua y conductividad. Las muestras fueron analizadas con microscopio óptico con contraste de fases y microscopio electrónico de barrido. Diez taxones son nuevos registros para el área; Encyonema en la Amazonia peruano-colombiana y Encyonopsis en el sector colombiano. Encyonema neogracile var. tenuipunctatum, E. vulgare, Encyonopsis frequentis, Gomphonema augur var. sphaerophorum y G. contraturris se reportan por primera vez en Colombia; Encyonema venezolanum y Gomphonema neoapiculatum en Colombia y Perú y la última también en la Amazonia. E. angustecapitatum fue previamente registrada en una laguna de altura en Colombia localizada a 3.000 msnm. Se describe una nueva especie, Encyonema amazonianum, colectada en el Río Porvenir, Amazonas, Colombia.