Abstract
In the tropical and subtropical regions, there is a large number of species which has not been yet described. The high possibility of extinction makes their inventory a priority. In this paper, 23 diatoms taxa from Andean lotic systems and lentic waterbodies localized in the Departments of Antioquia, Santander and Chocó, Colombia, are analyzed with light and scanning electron microscopy. Each taxon is described and information about environmental characteristic of the sites where they were collected and distribution in Colombia is given. The studied taxa belong to the orders Thalassiosirales (1), Aulacoseirales (1), Fragilariales (4), Cymbellales (7), Achnanthales (2), Naviculales (7), and Thalassiophysales (1). Fifteen of them are recorded for the first time in Colombia and Encyonema jemtlandicum in South America. A comparison with the diatom flora of the Colombian Amazonia showed that there were only three taxa in common to these two equatorial regions probably due to the influence of altitudinal gradient.
Highlights
The information about the Diatom flora of South America is incomplete and needs a careful revision on the basis of modern tools
Metzeltin and Lange-Bertalot (1998) pointed out that in warm or cold regions of South America there is a great number of species that are cosmopolitan or typical of temperate climatic zones, while in the tropical regions the flora is completely different, with exception of the areas with a high anthropogenic influence, and that many endemic taxa were found
The observations of Rumrich et al (2000) confirm these ideas with exception of many endemic taxa of high altitudes. These approaches are interesting as a start point of modern floristic studies in South America, but regional studies are still necessary for testing them because these analyses were based in a
Summary
The information about the Diatom flora of South America is incomplete and needs a careful revision on the basis of modern tools. The observations of Rumrich et al (2000) confirm these ideas with exception of many endemic taxa of high altitudes These approaches are interesting as a start point of modern floristic studies in South America, but regional studies are still necessary for testing them because these analyses were based in a. The geographical situation favors the existence of a great variety of geomorphologic and climatic situations in small areas as a consequence of high altitudinal gradients In this country, there are numerous records of diatom taxa in ecological studies about periphitic communities (Moreno 1989, Donato et al 1996, Montoya 1998), in paleoecological investigations (Lozano et al 1999), and studies about phytoplankton ecology (Ramírez and Machado 1982, Ramírez 1994, Ramírez and Díaz 1994, Asprilla et al 1998, Plata 2000, Ramírez et al 2000, among many others), the knowledge about morphology and taxonomy of freshwaters diatoms is scarce. The aim of this paper is to describe those taxa common to these three systems, and to give information about the conditions in which they were collected and about their distribution in Colombia
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