Boundaries

This ecoregion extends from the Rio Sixaola drainage in Costa Rica to the Rio Calovebora drainage basin in Panama.

Topography

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).

Freshwater habitats

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).

Terrestrial habitats

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).

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 [205] and Chagres [209] 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.

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.