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# of Endemic Species
207: Isthmus Caribbean
Major Habitat Type:
tropical and subtropical coastal rivers
William Bussing and Scott Smith contributed material to this text.
Costa Rica; Panama
This ecoregion extends from the Rio Sixaola drainage in Costa Rica to the Rio Calovebora drainage basin in Panama.
Drainages flowing into:
Main rivers or other water bodies:
The main river basins in the Isthmus Caribbean ecoregion include the Rio Sixaola, Rio San San, Rio Changuinola, Rio Uyama, Rio Robalo, Rio Guarumo, Rio Guariviara, Rio Cricamola, Rio Canaveral, and Rio Calovebora.
The Isthmus Caribbean ecoregion lies along the southwest corner of the Caribbean plate, and is bordered in the southwest by the mountains of the Cordillera Central, which are the highest in Panama (Kaufmann & Thompson 2005). Elevations reach over 3300 in the Cordillera Central, but quickly decline toward the Caribbean coast. Through most of its length the Cordillera Central runs much closer to the Caribbean Sea than to the Pacific Ocean, resulting in a Pacific slope that is much greater than the Caribbean slope (Angehr 2005).
This ecoregion encompasses the Archipelago of Bocas del Toro, which consists of a complex of islands, mainland bays, rivers, and forested mountain slopes on the Caribbean side of the Isthmus of Panama. The archipelago is naturally divided in two large semi-enclosed lagoons: the Chiriquí Lagoon and Almirante Bay (D\'Croz et al. 2005).
Average annual temperatures vary from as low as -8 oC in the mountains to around 25 oC at sea level (World Wildlife Fund 2001). The mean annual precipitation at Bocas del Toro is 3277 mm. Although there is no dry season, there is a relatively dry period in February and March, and another slightly drier period in September and October. The heaviest rain occurs in December, with high rainfall also occurring in July (Kaufmann & Thompson 2005).
There are numerous rapids along the rivers of the ecoregion as they descend quickly from the Cordillera Central to the coast. Floodplains and coastal lagoons occur along the lower portions of the rivers.
The Laguna de Chiriquí receives heavy freshwater discharge from several large rivers, resulting in high turbidity (Instituto Geografico Nacional Tomy Guardia 1988). Almirante Bay is home to numerous small islands, mangrove islets, and shoaling sand cays (D\'Croz et al 2005). The Damani wetlands, located in the southern part of the Laguna de Chiriquí, includes the freshwater lakes of Diablo, Jugli, and Samani, and extensive areas of freshwater swamp (Angehr 2005).
Talamancan montane forests occur at higher elevations where rainfall ranges from 2500-6000 mm per year. Lower elevations are dominated by Isthmian-Atlantic moist forests and mangroves along the coast (World Wildlife Fund 2001). Peat-swamp forest occurs along the coast of Almirante Bay.
Approximately 75% of the Talamancan montane forests are intact, although unprotected areas are being converted (World Wildlife Fund 2001). Deforestation is common in the lowlands and the larger islands in the Archipiélago de Bocas del Toro. Some old-growth forest still remains on Islas Colon and Bastimentos. Mangrove forests in the ecoregion occur along the mainland and larger islands, as well as on overwash islands within the Laguna de Chiriquí (Collin 2005).
Nearly 80 species of primary and secondary freshwater fishes inhabit the Isthmus Caribbean ecoregion. The majority of the freshwater fish fauna is composed of secondary freshwater fishes. However, there is a noticeable increase in the relative contribution of primary freshwater fishes to the Isthmus Caribbean ichthyofauna relative to the freshwater fish fauna of its northern counterpart, the San Juan ecoregion . The Characidae, a primary freshwater fish family, make up 20% of the freshwater fish fauna, wheras the Cichlidae and the Poeciliidae, secondary freshwater fish families, each constitute 13% and 14%, respectively, of the total species richness of this ecoregion. The ichthyofauna of the Isthmus Caribbean ecoregion is also characterized by the presence of a relatively large number of Rivulus species (10%).
Description of endemic fishes:
Molecular analyses and biogeographic distributional patterns of the lower Mesoamerican ichthyofauna indicate that the Isthmus Caribbean ecoregion is relatively isolated from its Caribbean slope neighbors, the San Juan  and Chagres  ecoregions. Speciation has clearly had a large impact on patterns of distribution and diversity in this region: 42% of the freshwater fish fauna is endemic to the province (Smith and Bermingham 2005). The faunal assembly of this ecoregion may contain species (e.g. Brachyhypopomus; see Bermingham and Martin 1998) derived from an early colonization event 7-4 Ma, followed by isolation from the rest of lower Mesoamerica approximately 3 Ma. Twelve of the 13 endemic species to this ecoregion are secondary freshwater fishes. There are five cichlids, including, Amphilopus bussingi, Archocentrus altoflavus, Archocentrus myrnae, Tomocichla asfraci, Archocentrus nanoluteus; 4 endemic species of rivulus, Rivulus birkhahni, R. kuelpmanni, R. wassamanni, R. monikae, and three poeciliids, Phallichthys quadripunctatus, Brachyrhaphis punctifer, Priapichthys puetzi. There is also one endemic primary freshwater fish species that is a characiid: Bryconamericus gonzalenzi.
Other noteworthy aquatic biotic elements:
This ecoregion spans two Endemic Bird Areas (EBAs): the Central American Caribbean Slope and Costa Rica and Panama Highlands. The western part of the ecoregion lies within the Amistad International Park, which contains nearly all of the endemics of the two EBAs (Montanez and Angehr 2007). The Damani wetlands and extensive areas of freshwater swamp are dominated by orey (Campnosperma panamensis) and a number of other wetland species.
More than 20 amphibian Red List species belonging to nine genera are found in this ecoregion, including species from the genera Isthmohyla, Craugastor, Duellmanohyla, Bufo, and Atelopus (GAA 2006).
Emydids of the genus Pseudemys occupy the widest distribution of any aquatic turtles in the area. Populations of the Pseudemys scripta series range throughout much of the Caribbean (McCoy 1982).
Justification for delineation:
Fish provinces from Bussing (1976) were revised and subdivided based on application of a similarity index to sub-basin fish presence/absence data.
Bussing, W. A. (1976)"Geographic distribution of the San Juan ichthyofauna of Central America with remarks on its origin and ecology" In Thorson, T.B. (Ed.). Investigations of Nicaraguan lakes. (pp. 157-175) Lincoln, Nebraska: University of Nebraska.
Smith, S. A.,Bermingham, E. (2005). "The biogeography of lower Mesoamerican freshwater fishes" Journal of Biogeography 32(10) 1835-1854.
World Wildlife, Fund (2001). "Terrestrial Ecoregions of the World" 2005 (2005; www.worldwildlife.org/science/ecoregions/biomes.cfm).