Synchrony between Reproductive Phase and Flood Period: A Dispersion Mechanism for the Freshwater Clam Corbicula fluminea (Bivalvia: Corbiculidae) in a Brazilian Neotropical Floodplain.

This study evaluates the gonadal histology of Corbicula fluminea present in the upper Paraná River floodplain and samples of limnological variables to understand its reproductive cycle. Corbicula fluminea was monitored monthly from December 2013 to February 2015. Spermatogonia, primary and secondary spermatocytes, spermatids and spermatozoa were identified in the male follicles of the hermaphrodites. Oogonia, oogonial nests, previtellogenic oocytes, early vitellogenic oocytes, middle vitellogenic oocytes and full-grown vitellogenic oocytes were identified in the female follicles of the hermaphrodites and females. The reproductive phases were described as developing, active spawning/sperm releasing, regression and regeneration. Higher values of temperature, dissolved oxygen, total nitrogen and total phosphorous were identified during flood periods, while higher values of pH and conductivity were obtained during dry periods. The species either does not reproduce or reduces the intensity of reproduction in cold months, with the sex ratio not differing significantly between hermaphrodites and females with regard to month and reproductive phase. Thus, reproduction is synchronized with the flood period and its limnological characteristics and when the increase in connectivity between floodplain environments facilitates the larval dispersion of this non-native species into other environments.

Non-native fishes homogenize native fish communities and reduce ecosystem multifunctionality in tropical lakes over 16 years.

Non-native species are considered a major global threat to biodiversity, and their expansion to new ecosystems has recently increased. However, the effect of non-native species on ecosystem functioning is poorly understood, especially in hyperdiverse tropical ecosystems of which long-term studies are scarce. We analyzed the relationship between richness, biomass, and ß-diversity of non-native and native fishes during 16 years in five hyperdiverse tropical shallow lakes. We further elucidated how an observed increase in the proportion of richness, biomass, and ß-diversity of non-native over native fishes affect crucial multifunctional processes of lakes (decomposition, productivity). We found a general positive relationship between the richness and biomass of non-native and native fishes. However, the slope of this relationship decreased continuously with time, displaying an increase in non-native species richness and a decrease in native species richness over time. We also detected a negative relationship between the ß-diversity of non-native and native fishes over time. Moreover, the increase in the non-native:native ratio of species richness, biomass, and ß-diversity over time decreased ecosystem multifunctionality. Our results suggest that non-native fishes caused a homogenization of the native fish species over time, resulting in impoverishment of ecosystem multifunctionality; in part because non-native fishes are less productive than native ones. Therefore, focus on long-term effects and use of multiple biodiversity facets (α- and ß-diversity) are crucial to make reliable predictions of the effects of non-native fish species on native fishes and ecosystem functioning.

Beta diversity as a tool for determining priority streams for management actions.

Beta diversity has become essential for understanding ecosystem functioning and for determining biodiversity-conservation priority areas. However, the beta diversity patterns of invertebrates in tropical aquatic ecosystems are not well known, particularly in streams. Using data from low-order streams located in southern Brazil, we evaluated the beta diversity of Chironomidae. We tested the hypothesis that increased environmental heterogeneity increases beta diversity. The streams were grouped into two categories, rural and urban, according to the percentage of urbanization in their micro-basins. Our results showed that the heterogeneity of environmental variables can determine the beta diversity of Chironomidae, and the increased environmental heterogeneity caused by differences in the intensity of urbanization impacts can increase the beta diversity in urban streams. Therefore, the intensified impacts of anthropogenic activities in aquatic ecosystems can also increase beta diversity. Finally, we suggested that beta diversity can be an effective tool for not only designing measures and determining priority conservation areas, but also accurately identifying potentially degraded and priority sites that require water management plans.

Richness and composition of macrophyte assemblages in four Amazonian lakes / Riqueza e composição da assembleia de macrófitas em quatro lagos amazônicos

Aquatic macrophytes are an important component in the structure of lakes in Neotropical floodplains, for example, because they support a high diversity of invertebrates and vertebrates. In this paper, we tested whether or not the variability of macrophyte assemblages is lower in spatially close quadrats than among quadrats of different lakes. The study was carried in four lakes in a large Amazonian floodplain (Purus river), where floating meadows were investigated. A total of 49 taxa of macrophytes were found. Five species dominated and three species were rare. Taxa richness, composition and beta diversity differed more between than within lakes. Because high beta diversity was found among the lakes, they should be considered individually important for maintaining the gamma diversity of macrophytes within the Purus River floodplain, and this should be considered in plans of lake management.

As macrófitas aquáticas são um importante componente para a estrutura de lagos neotropicais em planícies de inundação, porque suportam alta diversidade de invertebrados e vertebrados. Neste trabalho, nós testamos se a variabilidade da assembleia de macrófitas aquáticas é menor entre "quadrats" espacialmente próximos do que "quadrats" em lagos diferentes. O estudo foi desenvolvido em quatro lagos da planície amazônica (rio Purus), onde bancos flutuantes de macrófitas foram amostrados. Um total de 49 taxa de macrófitas foi encontrado. Cinco espécies dominaram e três espécies foram raras. A riqueza de taxa, composição e diversidade de espécies diferiram mais entre os lagos do que dentro dos lagos. Pela alta diversidade beta encontrada nos lagos, esses lagos devem ser considerados importantes individualmente para manter a diversidade gamma de macrófitas dentro da planície de inundação do rio Purus. Esse fato deve ser considerado em planos de manejo desses lagos de planície.

The study of fractals among ecologists / O estudo dos fractais entre os ecólogos

Fractals seemed to have permeated most scientific fields, including ecology. In fact, biodiversity and ecological processes are affected by spatial complexity, and fractals can help understand patterns at multiple scales. In this paper we evaluated the main quantitative trends and the profile of ecology publications using fractals. Publications about fractals in Ecology experienced a high increase in the last two decades, and most articles were published in highly visible ecology journals. However, studies were authored mainly by US scientists, and researchers from developing countries had a minor contribution. In addition, studies were highly biased towards terrestrial environments, and empirical approaches were preferred.

Os fractais pareciam ter permeado a maioria das áreas científicas, incluindo a ecologia. De fato, a biodiversidade e os processos ecológicos são afetados pela complexidade espacial, e os fractais podem ajudar a compreender esses padrões em múltiplas escalas. Neste trabalho avaliaram-se as principais tendências do perfil ecológico, bem como foram quantificadas as publicações utilizando fractais. Publicação sobre fractais em ecologia sofreram grande aumento nas últimas duas décadas e muitos artigos foram publicados em revistas de alta circulação. No entanto, os estudos foram escritos, principalmente, por americanos, e os pesquisadores de países em desenvolvimento tiveram contribuição menor. Além disso, os estudos foram desenvolvidos em sua maioria em ambientes terrestres, e as abordagens empíricas foram preferidas.

Macrophytes in the Upper Paraná River floodplain: checklist and comparison with other large South American wetlands.

Neotropical aquatic ecosystems have a rich aquatic flora. In this report, we have listed the aquatic flora of various habitats of the upper Paraná River floodplain by compiling data from literature and records of our own continuous collections conducted during the period 2007-2009. Our main purposes were to assess the macrophyte richness in the Paraná floodplain, to compare it with other South American wetlands and to assess whether the number of species recorded in South American inventories has already reached an asymptote. We recorded a total of 153 species of macrophytes in the Upper Paraná River floodplain, belonging to 100 genera and 47 families. In our comparative analysis, a clear floristic split from other South American wetlands was shown, except for the Pantanal, which is the closest wetland to the Paraná floodplain and, therefore, could be considered a floristic extension of the Pantanal. The species accumulation curve provides evidence that sampling efforts should be reinforced in order to compile a macrophyte flora census for South America. The high dissimilarity among South American wetlands, together with the lack of an asymptote in our species accumulation curve, indicates that the sampling effort needs to be increased to account for the actual species richness of macrophytes in this region.

Macrophytes in the upper Paraná river floodplain: checklist and comparison with other large South American wetlands

Neotropical aquatic ecosystems have a rich aquatic flora. In this report, we have isted the aquatic flora of various habitats of the upper Paraná River floodplain by compiling data rom literature and records of our own continuous collections conducted during the period 2007-2009. Our main purposes were to assess the macrophyte richness in the Paraná floodplain, to compare it with other South American wetlands and to assess whether the number of species recorded in South American inventories has already reached an asymptote. We recorded a total of 153 species of macrophytes in the Upper Paraná River floodplain, belonging to 100 genera and 47 families. In our comparative analysis, a clear floristic split from other South American wetlands was shown, except for the Pantanal, which is the closest wetland to the Paraná floodplain and, therefore, could be considered a floristic extension of the Pantanal. The species accumulation curve provides evidence that sampling efforts should be reinforced in order to compile a macrophyte flora census for South America. The high dissimilarity among South American wetlands, together with the lack of an asymptote in our species accumulation curve, indicates that the sampling effort needs to be increased to account for the actual species richness of macrophytes in this region. Rev. Biol. Trop. 59 (2): 541-556. Epub 2011 June 01.

Los ecosistemas acuáticos neotropicales tienen una rica flora acuática. En este informe, hemos hecho una lista de la flora acuática de diversos hábitats de la alta planicie de inundación del río Paraná mediante la compilación de datos de la literatura y los registros de nuestras colecciones propias realizadas durante el período 2007-2009. Nuestros principales objetivos fueron evaluar la riqueza de macrófitos en la llanura aluvial del Paraná, para compararlo con otros humedales de América del Sur y evaluar si el número de especies registradas en los inventarios suramericanos ya han alcanzado una asíntota. Se registraron un total de 153 especies de macrófitas en la llanura de inundación del Río Alto Paraná, pertenecientes a 100 géneros y 47 familias. En nuestro análisis comparativo, se mostró una clara división florística de otros humedales de América del Sur, con excepción del Pantanal, que es el más cercano a los humedales de la planicie de inundación del Paraná y, por tanto, podría considerarse una extensión florística del Pantanal. La curva de acumulación de especies demuestra que los esfuerzos de muestreo deben ser reforzados con el fin de elaborar un censo de la flora de acrófitos para América del Sur. La alta disimilitud entre los humedales de América del Sur, junto con la falta de una asíntota en nuestra curva de acumulación de especies, indica que el esfuerzo de muestreo debe ser mayor para dar cuenta de la riqueza real de las especies de acrófitos en esta región.

Aquatic macrophytes in the large, sub-tropical Itaipu Reservoir, Brazil

In the last three decades, rapid assessment surveys have become an important approach for measuring aquatic ecosystem biodiversity. These methods can be used to detect anthropogenic impacts and recognize local or global species extinctions. We present a floristic survey of the aquatic macrophytes along the Brazilian margin of the Itaipu Reservoir conducted in 2008 and compare this with a floristic survey conducted ten years earlier. We used ordination analysis to determine whether assemblage composition differed among reservoir arms. Macrophyte species were sampled in each of the 235 sampling stations using a boat, which was positioned inside three places of each macrophyte stand to record species and search for small plants. We also collected submerged plants using a rake with the boat moving at constant velocity for ten minutes. We assigned individual macrophyte species to life form and identified representative species for each life form. A total of 87 macrophyte taxa were identified. The "emergent" life forms contained the highest number of species, followed by "rooted submerged" life forms. The extensive survey of macrophytes undertaken in September 2008 recorded more species than a survey conducted between 1995 and 1998. This could be due to changes in water physico-chemistry, disturbances due to water drawdown and the long period between surveys, which may have allowed natural colonization by other species. Additionally, differences in the classification systems and taxonomic resolution used in the surveys may account for differences in the number of species recorded. Assemblage composition varied among the arms and was affected by underwater radiation (as measured using a Secchi disk) and fetch. Five non-native species were found. Two of these non-native species (Urochloa subquadripara and Hydrilla verticillata) are of special concern because they have a high frequency of occurrence and occupy large marginal areas of the reservoir. Future surveys should be conducted to determine the habitat most frequently colonized by these species. This would allow management strategies to be developed to protect native aquatic biota and prevent interference with the recreational and commercial uses of the Itaipu Reservoir. Rev. Biol. Trop. 58 (4): 1437-1452. Epub 2010 December 01.

En las últimas tres décadas, las evaluaciones ecológicas rápidas se han convertido en un método importante para medir la biodiversidad de los ecosistemas acuáticos. Estos métodos se pueden utilizar para detectar los impactos antropogénicos y reconocer las extinciones locales o globales de las especies. Se presenta un estudio florístico de las macrófitas acuáticas a lo largo del margen brasileño del embalse Itaipú en 2008 y se compara con un estudio florístico realizado diez años atrás. Se utilizó un análisis de ordenamiento para determinar si hay diferencias en la composición de asociaciones de especies entre los brazos del embalse. Se tomaron muestras de las especies de macrófitos en cada una de las 235 estaciones de muestreo utilizando una embarcación, que fue colocada en tres lugares por punto para registrar las especies de macrófitos y buscar plantas pequeñas. También se recolectaron plantas sumergidas mediante un barrido con la embarcación, moviéndose a velocidad constante durante diez minutos. A las especies de macrófitas individuales se les asignó una forma de vida y se identificaron especies representativas de cada una. Un total de 87 táxones de macrófitas fueron identificados. Las formas de vida "emergentes" tienen el mayor número de especies, seguido por las formas de vida "con raíces sumergidas". Un estudio amplio de los macrófitos realizado en septiembre de 2008 registró más especies que el estudio realizado entre 1995 y 1998. Esto podría deberse a cambios físico-químicos del agua, perturbaciones debidas al nivel del embalse y el largo período de tiempo que hay entre ambos estudios, que pudo haber permitido la colonización natural por otras especies. Además, diferencias en la clasificación de los sistemas y la resolución taxonómica usada en los estudios, que podría producir diferencias en el número de especies registradas. La composición de la asociación de especies varió entre los brazos y se vio afectada por la radiación bajo el agua (medido utilizando un disco de Secchi) y la obtención de información. Se encontraron cinco especies no nativas. Dos no son nativas (Urochloa subquadripara y Hydrilla verticillata) son de especial preocupación debido a que tienen una alta frecuencia de ocurrencia y ocupan grandes zonas marginales del embalse. Se deben llevar a cabo futuros estudios para determinar el hábitat más frecuentemente colonizado por estas especies. Esto permitiría desarrollar estrategias de manejo para proteger la biota acuática nativa y evitar interferencias con los usos recreativos y comerciales del embalse Itaipú.

Aquatic macrophytes in the large, sub-tropical Itaipu Reservoir, Brazil.

In the last three decades, rapid assessment surveys have become an important approach for measuring aquatic ecosystem biodiversity. These methods can be used to detect anthropogenic impacts and recognize local or global species extinctions. We present a floristic survey of the aquatic macrophytes along the Brazilian margin of the Itaipu Reservoir conducted in 2008 and compare this with a floristic survey conducted ten years earlier. We used ordination analysis to determine whether assemblage composition differed among reservoir arms. Macrophyte species were sampled in each of the 235 sampling stations using a boat, which was positioned inside three places of each macrophyte stand to record species and search for small plants. We also collected submerged plants using a rake with the boat moving at constant velocity for ten minutes. We assigned individual macrophyte species to life form and identified representative species for each life form. A total of 87 macrophyte taxa were identified. The "emergent" life forms contained the highest number of species, followed by "rooted submerged" life forms. The extensive survey of macrophytes undertaken in September 2008 recorded more species than a survey conducted between 1995 and 1998. This could be due to changes in water physico-chemistry, disturbances due to water drawdown and the long period between surveys, which may have allowed natural colonization by other species. Additionally, differences in the classification systems and taxonomic resolution used in the surveys may account for differences in the number of species recorded. Assemblage composition varied among the arms and was affected by underwater radiation (as measured using a Secchi disk) and fetch. Five non-native species were found. Two of these non-native species (Urochloa subquadripara and Hydrilla verticillata) are of special concern because they have a high frequency of occurrence and occupy large marginal areas of the reservoir. Future surveys should be conducted to determine the habitat most frequently colonized by these species. This would allow management strategies to be developed to protect native aquatic biota and prevent interference with the recreational and commercial uses of the Itaipu Reservoir.