Boundaries

Cuatro Ciénegas is located in an intermontane valley in the Mexican state of Coahuila.

Topography

The ecoregion is located in an intermontane valley of the Sierra Madre Oriental, with elevations ranging between 750 and 2700 m above sea level.

Freshwater habitats

Cuatro Ciénegas in Spanish means "four marshes" and describes an extensive network of geothermal springs, lakes, and streams. Over 500 posas (spring pools) have been counted in the ecoregion. Other aquatic habitats include several sub-drainages, marshes, rivers, saline lakes (locally called lagunas or playas), canals, and terminal lagoons.

Waters in Cuatro Ciénegas have a wide diversity of qualities, from thermal to cool springs, clear to turbid, fresh to saline to gypsum loaded. This has resulted in great habitat diversity among the springs, with extreme variation often within small spatial scales.

Terrestrial habitats

The ecoregion falls primarily within the Chihuahuan Desert, but supports vegetation not entirely typical of this desert ecoregion. Vegetation communities range from halophilic, aquatic, and semi-aquatic to grasslands, gypsum dune assemblages, scrub, chaparral, and pine-oak forests.

Description of endemic fishes

The diversity of habitats, stable ecosystems, and geographical isolation has resulted in a high level of endemism through adaptive radiation and speciation. Endemic species within the ecoregion include Minkley’s cichlid (Cichlasoma minckleyi), Cuatro Ciénegas shiner (Cyprinella xanthicara), Bolson pupfish (Cyprinodon atrorus), Cuatro Ciénegas pupfish (C. bifasciatus), Tufa darter (Etheostoma lugoi), Cuatro Ciénegas gambusia (Gambusia longispinis), Cuatro Ciénegas killifish (Lucania interioris), and northern platyfish (Xiphophorus gordoni). Minkley’s cichlid is particularly interesting because it exhibits two distinct morphs.

Ecological phenomena

Waters in Cuatro Ciénegas have a wide diversity of qualities, from thermal to cool springs, clear to turbid, fresh to saline to gypsum loaded. This has resulted in great habitat diversity among the springs, with extreme variation often within small spatial scales.

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. The delineation of this ecoregion was based on high levels of endemism among the flora and fauna, probably expressed in nearly 200 species, including some genera, where fishes are one of the most interesting. The fish fauna is derived from Lower Rio Grande/Río Bravo [135] ecoregion fauna, and most species are endemic due to the ecoregion’s isolation, water quality, and high occurrence of springs. The Neotropical species of characid, poeciliids, and cichlid are relict and, with other endemics in Río Pecos, related to more southern groups. In contrast, the Nearctic forms of cyprinids, ictalurids, centrarchids and percids are close to Rio Grande stocks.

Level of taxonomic exploration

The ecoregion has been intensely studied, although it still harbors little known, undescribed, or unstudied taxa.