Santiago R. Duque

Diatoms from the Colombian Amazon: some species of the genus Eunotia (Bacillariophyceae)

This research was carried out in three of the most important basins of the Colombian Amazon (Upper Solimoes, Ica and Japura Rivers). The creeks and lakes that were studied contain abundant diatom species, particularly those of the genus Eunotia. Ten species are described; five of them are registered for the first time in the Amazon basin, and six in all of Colombia. All taxa were photographed with scanning electron microscopy. Fine valve morphology of E. anamargariate, E. pseudoindica, E. triodon, and E. zydodon var. compacta is described for the first time.

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.

Brachysira (Naviculales, Bacillariophyceae) in lowland waters from Colombia

This study focuses on the genus Brachysira Kützing from lowland waters as part of the diatom flora investigation of Colombia. Periphyton samples were collected in lentic and lotic waterbodies from different Amazonian basins and the Ayapel swamp system in the northern Atlantic plain of Colombia. Diatoms were analysed with light and scanning electron microscopy. Two new taxa, B. guarrerai and B. huitotarum, are described. These species were differentiated from their allied taxa based on the combination of: the shape of the central area; the shape and number of the areolae that delimit the central area; stria position; presence or absence of papillae on the interstriae; and degree of silicification of the ribs that delimit the raphe. In addition, five other taxa are reported and described: B. microcephala (Grunow) Compère and B. subrostrata Lange-Bertalot are recorded for the first time from Colombia, while B. manfredii Lange-Bertalot was previously found in the Sierra Nevada. The other two taxa were identified as B. aff. brebissonii Ross and B. aff. microcephala because the Colombian specimens differ slightly from the type material of these cosmopolitan species.

A taxonomic and ultrastructural study of naked Euglenophyta from Colombia

A fl oristic and ultrastructural study on naked green Euglenophyta was performed in the Amazonian and Caribbean regions of Colombia, where a large number of taxa are contained in several freshwater bodies. A total of 37 taxa were recorded, 1 belonging to the genus Cryptoglena Ehr., 9 to Lepocinclis Perty, 1 to Monomorphina Meresch., and 26 to Phacus Duj. From the identifi ed taxa, 22 were recorded for the fi rst time in Colombia, 2 in the Amazonian region, and 14 in the Caribbean region. Among the taxa described in this work we propose Phacus sesquitortus var. longicauda as a new variety. In addition, 9 taxa were examined by scanning electron microscopy (SEM) to illustrate in detail their ultrastructure; 3 of them were examined for the fi rst time under this method.

Amino acid composition reveals functional diversity of zooplankton in tropical lakes related to geography, taxonomy and productivity

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.

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

Abstract 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.