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La Santisima Trinidad, Bolivia

The inventory of fish species of the río Mamoré sub-drainage in the Bolivian Amazon is far from being complete. This article informs about a small scale species inventory in the close vicinity of the town Santa Ana del Yacuma (drained by the río Yacuma, a left side tributary of the río Mamoré). Sampling four habitat types, 615 fish specimens belonging to 101 species were collected. Four species were reported for the first time from the río Mamoré sub-drainage: Aphyocharax rathbuni, Apistogramma erythrura, Apistogramma similis and Hyphessobrycon elachys. Differences in species composition among sampled habitats stress the importance of including a high number of collecting sites across biotic and abiotic environmental gradients to reliably survey species diversity. Source

Hablutzel P.I.,Autonomous University of Beni | Hablutzel P.I.,Catholic University of Leuven | Pantel J.H.,CNRS Center of Evolutionary and Functional Ecology

In freshwater ecosystems, spatial turnover in fish assemblages is often attributed to dispersal limitation imposed by fragmentation of water bodies. Other factors like environmental properties or biotic interactions have often been assumed to be minute relative to dispersal limitation when hydrogeological barriers are abundant. This study aims to describe the spatial differentiation of cichlid fish assemblages in the upper río Madera in Bolivia, Brazil and Perú, a large drainage system characterized by the absence of significant hydrogeological barriers. We assessed the relative importance of spatial, climatic and geological predictors in the observed biogeographic structure using an integrative combination of cluster analyses, elements of metacommunity structure analysis, variation partitioning, and network analysis. Our results show that distinct assemblages of cichlid fish species replace each other across the landscape and that this turnover is partially determined by climate and geological gradients. A considerable fraction of the cichlid assembly structure could not be assigned to either space, climate or geology and might be explained by unmeasured parameters such as habitat structure or biotic interactions. Incorporating knowledge on spatial turnover of species assemblages into conservation strategies will be essential for the biodiversity management of the diverse aquatic fauna of the upper río Madera. © 2016 Springer International Publishing Switzerland Source

The causes of fish community organization in a system of habitat patches with different environmental conditions were described using a data set of 65 sites sampled during the dry season. Incorporating the patchy heterogeneous structure, variation partitioning allowed us to specifically evaluate the fine-scale neutral processes produced by spatial autocorrelation within habitat patches, and the broad-scale dispersal limitations between patches. Only the second subset of spatial variables was significant; dispersal limitation was relatively low between habitat patches of varzea lakes. An analysis of functional ecology allowed an empirical description of the functional mechanisms of alpha and beta niche differentiation, and an assessment of the phylogenetic signal. The trait-convergence assembly pattern among habitat patches indicated that fish in turbid river channels were better adapted to low light than fish in transparent black and clear water bodies. Also, fish in varzea lakes had a wider ecological range; this association indicated phylogenetic niche conservatism. The trait-divergence assembly pattern was almost expressed by body weight and was prominent in varzea lakes; combined with ecological range and sensory adaptation, this association indicated a marginal phylogenetic signal. These results suggest the radiation of species-rich clades with a high degree of sensory adaptation may have occurred in the seasonal environment of varzea lakes. This resulted in larger ecological distribution and innovative life histories tightly synchronized with periodic flooding. The lineage-specific sensory adaptation and subsequent landscape and evolutional history of habitat specialization were also found to actually contribute to the fish metacommunity dynamic in the Bolivian Amazonian lowland. © 2016 Springer Science+Business Media Dordrecht Source

Soliz-Gamboa C.C.,University Utrecht | Soliz-Gamboa C.C.,Autonomous University of Beni | Rozendaal D.M.A.,University Utrecht | Rozendaal D.M.A.,Autonomous University of Beni | And 4 more authors.
Trees - Structure and Function

Knowledge on juvenile tree growth is crucial to understand how trees reach the canopy in tropical forests. However, long-term data on juvenile tree growth are usually unavailable. Annual tree rings provide growth information for the entire life of trees and their analysis has become more popular in tropical forest regions over the past decades. Nonetheless, tree ring studies mainly deal with adult rings as the annual character of juvenile rings has been questioned. We evaluated whether juvenile tree rings can be used for three Bolivian rainforest species. First, we characterized the rings of juvenile and adult trees anatomically. We then evaluated the annual nature of tree rings by a combination of three indirect methods: evaluation of synchronous growth patterns in the tree-ring series, 14C bomb peak dating and correlations with rainfall. Our results indicate that rings of juvenile and adult trees are defined by similar ring-boundary elements. We built juvenile tree-ring chronologies and verified the ring age of several samples using 14C bomb peak dating. We found that ring width was correlated with rainfall in all species, but in different ways. In all, the chronology, rainfall correlations and 14C dating suggest that rings in our study species are formed annually. © 2010 The Author(s). Source

Rozendaal D.M.A.,University Utrecht | Rozendaal D.M.A.,Autonomous University of Beni | Rozendaal D.M.A.,Michigan State University | Zuidema P.A.,University Utrecht | Zuidema P.A.,Autonomous University of Beni
Trees - Structure and Function

Over the last decade the field of tropical dendroecology has developed rapidly and major achievements have been made. We reviewed the advances in three main themes within the field. First, long chronologies for tropical tree species were constructed which allowed climate reconstructions, revealed sources of climatic variation and clarified climate-growth relations. Other studies combined tree-ring data and stable isotope (13C and 18O) measurements to evaluate the response of tropical trees to climatic variation and changes. A second set of studies assessed long-term growth patterns of individual trees throughout their life. These studies enhanced the understanding of growth trajectories to the canopy, quantified autocorrelated tree growth and yielded new estimates of tree ages. Such studies were also used to reconstruct the disturbance history of tropical forests. The last set of studies applied tree-ring data to growth models. Tree-ring data can replace diameter measurements from research plots, provide additional information to construct population models, improve timber yield models and validate model output. Based on our review, we propose two main directions for future research. (1) An evaluation of the causes and consequences of growth variation within and among trees and their relation to environmental variation. Studies evaluating this directly contribute to improved understanding of tropical tree ecology. (2) The simultaneous measurement of widths and stable isotope fractions in tree rings offers the potential to study responses of trees to climatic change. Given the major role of tropical forests in the global carbon cycle, knowing these responses is of high priority. © 2010 The Author(s). Source

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