Boundaries

This ecoregion encompasses a small part of southern Nayarit, southern Jalisco, northwestern Michoacán, and the entire state of Colima. Its extent is determined by the watersheds of the Río Ameca in the north and the Río Ahuijallo in the south.

Topography

The ecoregion is mountainous, and traversed by numerous canyons. Elevations range from sea level to nearly 4000 m.

Freshwater habitats

Freshwater habitats are characterized by coastal or short course rivers, with narrow or non-existent floodplains, especially in the northern areas.

Terrestrial habitats

Terrestrial habitats include primarily dry forests and pine-oak forests, with stands of mangroves along the coast.

Description of endemic fishes

The Ameca-Manantlán is distinctive because of its endemism, especially among fish. Over half of its fish are endemic, and it has one endemic species of aquatic herpetofauna. Endemics usually occupy only one of the small basins within the ecoregion, except for Poeciliopsis, which is known to extend throughout the ecoregion in highly saline waters. There are a large number of endemic splitfins (Goodidae), including whitepatched splitfin (Allodontichthys hubbsi), finescale splitfin (A. polylepis), tuxspan splitfin (A. tamazulae), bandfin splitfin (A. zonistius), butterfly splitfin (Ameca splendens), goldbreast splitfin (Ilyodon furcidens), Limones splitfin (Ilyodon xantusi), golden skiffia (Skiffia francesae), leopard splitfin (Xenotaenia resolanae), black splitfin (Xenotoca melanosoma), and Tequila splitfin (Zoogoneticus tequilae). Some endemics in the Poeciliidae family include dwarf molly (Poecilia chica), golden livebearer (Poeciliopsis baenschi), and blackspotted livebearer (P. turneri). An endemic minnow, Algansea aphanea, is also found in the ríos Coahuayana and Armerìa.

Justification for delineation

Ecoregion delineations were based on qualitative similarity/dissimilarity assessments of major basins, using the standard administrative hydrographical regions of the Mexican federal government. This ecoregion represents a transition between the Río Santiago [164] to the north and Río Balsas [169] to the south. It also harbors a number of endemics.

Level of taxonomic exploration

Poor, until recently. Explorations are continuing in the ecoregion.