The invasive ctenophore, Mnemiopsis leidyi, which had its first mass occurrence in Limfjorden (Denmark) . During that period, copepods and other mesozooplankton organisms were virtually absent while ciliates were a substantial part of the zooplankton biomass. In "pre-Mnemiopsis years", there seems to have been large variability in the grazing impact on zooplankton depending on the seasonal abundance of A. aurita. With the addition of the second carnivore M. leidyi, however, additional predation pressure caused the zooplankton stocks to be severely depressed throughout 2008 and 2009 when copepods and cladocerans no longer showed the high seasonal peaks in abundance typical of previous years.

No abstract

Variación genética deRESUMEN. Dentro de la familia Cambaridae el género Procambarus es especialmente importante debido al número de especies que contiene y a su amplia distribución en el continente americano. Procambarus (Austrocambarus) llamasi es una especie endémica de la península de Yucatán, distribuyéndose en cuerpos de agua epicontinentales, incluyendo lagos, pantanos y planicies de inundación, que pueden estar relativamente aislados. Debido a la naturaleza fragmentada de su hábitat se esperaría encontrar poblaciones muy estructuradas con haplotipos únicos. Para describir la variación genética de las diferentes poblaciones de P. llamasi y su patrón de distribución se realizó un análisis filogeográfico usando el gen mitocondrial COI. Se secuenció un fragmento de 643 pares de bases de 53 organismos en diez poblaciones. Se identificaron los diferentes haplotipos y se construyó una red usando parsimonia estadística para realizar un análisis de clados anidados. Se encontró un total de 14 sitios variables, de los cuales 12 fueron informativos; todos los cambios nucleotídicos fueron transiciones y la diversidad nucleotídica fue de π = 0,0045. Se encontraron 10 haplotipos con una diversidad haplotípica de HD = 0,532, con uno de ellos ampliamente distribuido. El análisis de clados anidados muestra que los haplotipos actuales son el resultado de una expansión contigua del intervalo de distribución, sugiriendo que el origen de la expansión se ubicó en el sector sur de la península. Esto puede ocurrir debido a las inundaciones estacionales en la región, que pueden crear conexiones temporales entre poblaciones. Palabras clave: Procambarus llamasi, variación poblacional, COI, dispersión, península de Yucatán, México. Genetic variation inProcambarus llamasi (Crustacea: Decapoda: Cambaridae) from the Yucatan Peninsula: evidence of connectivity in a fragmented landscape ABSTRACT. Within the family Cambaridae, the genus Procambarus is especially important due to the number of species it contains and its wide distribution in the American Continent. Procambarus (Austrocambarus) llamasi is endemic to the Yucatan Peninsula, distributed in epicontinental water bodies, including lakes, marshes and flood plains, which may be relatively isolated. Due to the fragmented nature of its habitat, it might be expected to find highly structured populations with unique haplotypes. To describe the genetic variation of the different populations of P. llamasi and their distribution pattern, a phylogeographic analysis was performed using the mitochondrial COI gene. A 643 base pair fragment was sequenced from 53 individuals of ten populations. Different haplotypes were identified and a haplotype network was built using statistical parsimony for nested clade analysis. A total of 14 variable sites were found, 12 of which were informative; all nucleotide changes were transitions and nucleotide diversity was π = 0.0045. Ten haplotypes were found with a diversity of HD = 0.532, with one of them widely distributed. The nested clade analysis shows tha...

RESUMEN. Se comunica el hallazgo de una nueva especie de origen sur Pacífico, Pinnixa valdiviensis Rathbun, 1907 (Decapoda, Pinnotheridae) en bahía de San Julián (49°17'48"S, 67°43'30"W), provincia de Santa Cruz, Argentina. Se registra la relación de comensalismo existente con el equiúrido Pinuca chilensis (Max Müller, 1852). Se amplía su área de distribución geográfica hacia el océano Atlántico sudoccidental y se incorpora como una nueva especie para el mar argentino. Se proporcionan datos morfométricos.

Forest soils respond dramatically to management changes compared to other soils influenced by different land-use forms. This work aimed to compare the soil conditions in four different zones in a temperate forest in a biosphere reserve in Mexico, using a minimum data set (MDS) based on volcanic soils properties to develop a soil quality index (SQI). For this purpose, two different MDSs were used, one obtained from an expert opinion and the other through a multivariate principal component analysis (PCA). The soil quality assessment was conducted in a biosphere reserve in Mexico, where volcanic soils predominate. Four different areas were studied. Overall, six different types of SQI were calculated for each area, for which linear and nonlinear functions were used and the additive and weighted method. The six SQI showed a significant difference between the four areas of study. The zone with the highest SQI values was the zone with a preserved pine forest, followed by the zone with a pine forest managed by the population, and the zones with a pine forest and grassland in recovery showed the lowest SQI. The linear score indices obtained by the PCA indicated the better ability to differentiate the calculated SQI values, which would provide information to contribute to the stakeholder management and decision making in the protection, conservation and management of the ecosystems present in the biosphere reserve.