Discussion
Endemic species
Type localities
As discussed by Cala (1981) and evident from the information in the Checklist, many type ranges of species described by those authors remain missing despite efforts to locate that material by Cala and other Colombian ichthyologists.
Why so many species?
Further contributing to the species-level richness of the continental Colombian fish fauna is the diversity of water types in the country's drainages. The major types of drainage system include white water streams and rivers that carry significant suspended sediment loads eroded from the slopes of the Andes and the Piedmont highlands, various clear water drainages, and acidic black water rivers that flow through and drain the lowland rainforests. Many fish species are specialized physiologically and anatomically for life in particular types of water; a connection reflected in their geographical distributions.
This results in large shifts in the composition of fish faunas at both species and generic levels between rivers of different water types. Soil types not only affect water chemistry and levels of suspended solids, but directly affect the form of riparian vegetation (e.g., rainforest versus savanna) bordering watersheds; variation, which in turn has consequences for the ichthyofauna. Alternative vegetation types along the stream margin result in different degrees of shade, a factor that affects the presence versus absence of some fish species.
Many species of fish specialize in exploiting certain types of animals and plants that fall into streams and water bodies, with alternative foods leading to differences in the composition of fish communities. Similarly, differences in the types of plants bordering a water body result in differences in the substrates and complexity of subaquatic habitats (leaves and woody detritus of different scales; different degrees of submergence of terrestrial plant parts along water edges) used by different fish species. The range of topographic relief in Colombia creates marked differences in water conditions that go beyond water chemistry, and is another factor that contributes to the specific nature of the country's freshwater ichthyofauna.
Many species of freshwater fish in that fauna are specialized for lentic water conditions common in rivers, cienagas (ponds and marshes) and. Similar lentic systems are common in the llanos (floodplains) of the Rio Orinoco basin and in the Amazon lowlands. However, other species are adapted to life in the faster-flowing mid-altitude rivers and streams of the piedmonts of the Andean Cordillera and in isolated highlands such as the Sierra Nevada de Santa Marta and the Serranias de La Macarena and Chiribiquete.
At the other extreme are dozens of species with the morphological, physiological and behavioral adaptations prerequisite for living in the fast-flowing Andean rivers and streams in the western, central and eastern Cordilleras (Maldonado-Ocampo et al. 2005) and the Sierra Nevada de Santa Marta. Differences in stream structure often correlate with altitudinal gradients and further affect the distribution of many species. The sum of the differences in velocity, water temperature, and primary productivity across the drainage systems of Colombia results in fish communities that differ not only in species-level richness and composition, but also in overall fish biomass.
Future Directions
Underlying soil types that vary in acidity, dissolved solids, and available nutrients often result in dramatically different water chemistry, both between and within watersheds. These phenomena of varying community composition and relative biomass occur to varying degrees across the spectrum of large river systems (e.g., the blackwater Rio Negro, Goulding et al.). Different forms of riparian vegetation also determine the type and levels of immigrant animal and plant species. input into water bodies.
The sum of the differences in velocity, water temperature, and primary productivity across the drainage systems of Colombia results in fish communities that differ not only in species-level richness and composition, but also in overall fish biomass. . the multiple species in what was previously recognized as Creagrutus heni Vari & Harold 2001: 78). One example involves the 67 now recognized species of Creagrutus; a number three and a half times the 19 species recognized in the genus before 1994 (Harold &.
Conservation challenges
Freshwater ecoregions of the world: a new map of biogeographic units for freshwater biodiversity conservation. Seven new species of the Neotropical electric fish Gymnotus (Teleostei, Gymnotiformes) with a redescription of G. Phylogenetic relationships of the sucker-mouthed armored catfishes (Loricariidae) with emphasis on the Hypostominae and the Ancistrinae.
The genus Peckoltia with description of two new species and a reanalysis of the phylogeny of the genera of Hypostominae (Siluriformes: Loricariidae). Systematics of the neotropical catfish genera Nemuroglanis Eigenmann and Eigenmann 1889, Imparales Schultz 1944 and Medemichthys Dahl 1961 (Si-luriformes: Heptapteridae). Redescription of the type species of Odontostilhe Cope, 1870 (Teleostei: Characidae: Cheirodontinae), and description of three new species from the Amazon basin.
Detritivores of the South American fish family Prochilodontidae (Teleostei: Ostariophysi: Characiformes): a phylogenetic and revisional study. Three new species from the diverse, sympatric Gymnotus group of electric fishes (Gymnotiformes: Gymnotidae) in the Amazonian lowland basin, with notes on ecology. Molecular phylogeny of Austrofundulus Myers (Cyprinodontiformes: Rivulidae), with revision of the genus and description of four new species.
Revision of the Hyphessobrycon heterorhabdus group (Teleostei: Characiformes: . Characidae), with description of two new species from Venezuela. A review of the South American cichlid genus Cichla, with descriptions of nine new species (Teleostei: Cichlidae). An environmental reconstruction of the paleo-Amazon river system (Middle-Late Miocene, NW Amazonia.
Two new cis-Andean species of the South American catfish genus Megalonema allied to trans-Andean Megalonema xanthum, with description of a new subgenus (Siluriformes: Pimelodidae). Revision of the Neotropical fish genus Hydrolycus (Ostariophysi: Characiformes: Cynodontidae) with description of two new species. Phylogenetic study of the Neotropical fish genera Creagrutus Giinther and Piabina Reinhardt (Teleostei: Ostariophysi: . Characiformes), with a revision of the Cis-Andean species.