Abstract
Background. Microorganisms have traditionally been considered cosmopolitan. Nevertheless, recent studies of diverse groups demonstrated that this is an erroneous concept. Reviews of diatoms from the Neotropics have shown high biodiversity and numerous endemic species. Colombia has great habitat diversity in relatively small areas due to its latitudinal position and topography, so it is an ideal site for biogeographic studies. One of the better represented genera in lowlandrivers, Eunotia and Eunotia parasiolii, a Neotropical species, was reported in several countries in the region. Goals. In order to establish whether the three morphotypes found are discrete taxonomic entities, their morphometric data, fine morphology and geographical distribution were analyzed. Methods. 170 periphyton samples corresponding to 83 lotic systems were analyzed. Samples were prepared following the CENT/TC 230 (2002) protocol. They were observed with light (LM) and scanning electronic microscope (SEM). Distribution maps were made using GIS and a Moran’s I autocorrelation spatial index was applied. Results. The analyses of several specimens collected at 83 lotic systems allowed us to differentiate a priori 3 morphotypes based on the valve outline, development of subapical costae, and striae density. The species was extensively distributed in the study area, in basins with different hydrogeomorphology and chemical characteristics. The morphological characteristics that distinguish these morphotypes varied gradually; besides, the morphotypes were randomly distributed. Conclusions. We conclude that Eunotia parasiolii is a species with a great morphological variability and wide distribution. We propose to emend the description of the species, since the original diagnosis does not include characteristics of the fine structure of the frustules and therefore is insufficient to differentiate it from its allied taxa.
Highlights
Vistas generales de las valvas mostrando el rango de variación; se indican las costillas subapicales, el engrosamiento en el extremo proximal del rafe y las helictoglossae. 40-45) microscopio electrónico de barrido (MEB). 40) Vista valvar interna, las puntas de flecha blancas marcan el engrosamiento silíceo en el extremo proximal del rafe
Los resultados obtenidos a partir del análisis con microscopía óptica y electrónica de más de 100 ejemplares provenientes de diferentes regiones de Colombia, permitieron conocer nuevos detalles de la ultraestructura del frústulo, incluyendo características de la vista conectival y de las valvas en vista interna
Summary
En la figura 1 se describe la ubicación de los sitios de muestreo en cada una de las cuencas, de donde se tomó la información para el presente análisis. Los ríos pertenecientes a las unidades RCO_VOR, RCO_VOC, RCC_VOR son sistemas típicos de piedemonte, que se caracterizan por una alta variación temporal del flujo, con lechos dominados por sustratos duros (bloques principalmente), con presencia de rápidos y flujo turbulento, así como altos valores de pH (= 8.0). Los ríos de la región del Putumayo (RAMAZ), se caracterizan por presentar alta cobertura vegetal, con predominio de zonas de corriente con lechos dominados por gravas, pH neutro ( = 6.7) y baja conductividad ( = 88.2 μS.cm). Las muestras fueron tratadas con H2O2 al 40% para retirar la materia orgánica, se siguió el protocolo CENT/TC 230 (2002) para análisis con microscopía óptica (MO) y microscopía electrónica de barrido (MEB); las mismas se depositaron en el Laboratorio de Biotecnología del Instituto Colombiano del Petróleo, con los números detallados en la tabla 2
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