Boundaries

This ecoregion lies along the Caribbean coast of Panama, and extends from the eastern boundary of the Río Calovebora in the west to the eastern boundary of the Río Acla in the east. 

Topography

The interior boundary of the ecoregion runs along the end of the Cordillera Central, the Cordillera de San Blas, and part of the Serranía del Darién. Elevations range from over 1300 m above sea level (asl) in the Cordillera Central to only about 150 m asl in the east. The coastal plain is short throughout the Chagres ecoregion, but particularly short in the east where the mountains nearly meet the sea.

Freshwater habitats

Historically, the Chagres ecoregion was characterized by short and steep coastal rivers and longer coastal rivers with extensive floodplains and lagoons. Today, there are few inland aquatic habitats in Panama. The most extensive of these are around the artificial reservoirs of Lake Gatún and Lake Alajuela (Angehr 2005). The small lakes and swamps around these two large lakes produce large amounts of methane from decaying aquatic vegetation (Condit et al. 2001).

Rainfall influences stream flow in the ecoregion, with the driest months occurring from January through March (Angermeier & Schlosser 1989). The headwaters of the Río Chagres – Frijolito, Frijoles, and Quebrada Juan Grande – are small forest streams that typically have continuous flow, but can rapidly become hypoxic when stagnant in backwaters, flood channels, and pools of temporary tributaries. A less common phenomenon occurs during the late dry season when the main channels become stagnant, trapping fish in larger hypoxic pools (Kramer, unpubl. obs.; Kramer 1983).

Terrestrial habitats

Lowland moist forests (including Isthmian Atlantic moist forests and Chocó-Darién moist forests) historically covered most of the ecoregion (World Wildlife Fund 2001). Today, forests near the Atlantic coast have almost no deciduous trees (Condit et al. 2000). Talamancan montane forests are still found at higher elevations, and the remote forests east of Lake Alajuela are largely undisturbed, with extensive areas of near pristine old-growth trees.

Description of endemic fishes

There is one strictly endemic species that inhabits this ecoregion: the characiid Roeboides carti. Some near-endemics include the characids Brycon chagrensis, Odontostilbe mitoptera, and Guatemalan headstander (Roeboides guatemalensis); and the aplocheilid, Rivulus montium (Smith and Bermingham 2005).

Justification for delineation

Fish provinces from Bussing (1976) were revised and subdivided on the basis of application of a similarity index to sub-basin fish presence/absence data.

Level of taxonomic exploration

The level of taxonomic exploration in the Chagres ecoregion is particularly good in the Río Chagres basin, as well as in the Río Cocle del Norte , Río Miguel de la Borda, and the Río Indio. Many of the small drainage basins found in Kuna Yala have also been well explored.