Chihuahuan Freshwater - A Global Ecoregion

Globally outstanding evolutionary radiations

The Rio Conchos is the main source of irrigation water for crops grown in the state of Chihuahua, Chihuahua Desert, Mexico.

Snapshot: Ecoregion 194

Size:
898,000 sq. km (350,000 sq. miles)

Habitat type:
Xeric Basins

Geographic Location:
North America: southeast Arizona across New Mexico and west Texas and southward deep into Mexico

Conservation Status:
Critical/Endangered

Did You Know!

Some aquatic species of this ecoregion have the unique ability to tolerate extremely high temperatures in thermal springs.

For example, in San Diego Springs, the bighead pupfish and an undescribed Gambusia species survive in water temperatures as high as 44^oC, the highest known temperatures in the world inhabited by freshwater fish!

About the Area
The Chihuahuan freshwater habitats support a diverse subtropical desert basin fauna with a high degree of local endemism. The river basins of this xeric ecoregion are remarkably different from one another, each containing unique species that have evolved overtime following a series of tectonic events and resulting geographic isolation.

Local Species
Within Cuatro Ciénegas, an interior basin containing hundreds of spring-fed pools in a desert environment, about half of the 20 species of fish, and 23 of the 34 species of freshwater mollusks are endemic. Some of these fish and mollusk species are restricted to individual pools of only a few square meters in size. Others have not changed appreciably from ancestral forms and are important relict species.

Species here include the aquatic box turtle (Terrapene coahuila), the endemic black softshell turtle (Trionyx ater), pond slider (Pseudemys scripta), plain-bellied water snake (Nerodia erythrogaster), and Cuatro Ciénegas cichlid (Cichlasoma minckleyi).

Three endangered endemic fishes are Cuatro Ciénegas shiner (Notropis xanthicara), Cuatro Ciénegas darter (Xiphophorus gordoni), and Sardinilla (Lucania interioris). Other endemic fishes are Cuatro Ciénegas gambusia (Gambusia longispinis), Robust gambusia (G. marshi), Yellowfin gambusia (G. alvarezi), Conchos pupfish (Cyprinodon eximius), Comanche springs pupfish (C. elegans), Bighead pupfish (C. pachycephalus), Devil's River minnow (Dionda diaboli), and Roundnose minnow (D. episcopa).

Tiny fish called Pecos gambusia give birth to live offspring rather than laying eggs. They also feed on mosquito larvae, helping to keep the mosquito population in check.

Among the endemic invertebrates, which are found predominantly in spring-fed habitats, are a number of aquatic snails and amphipods such as the Pecos assiminea (Assiminea sp.), Phantom Spring cochliopa (Cochliopa texana), Phantom Lake tryonia (Tryonia cheatumi), Phantom Spring amphipod (Gammarus hyalelloides), San Solomon amphipod (G. sp.), and Noel's amphipod (G. desperatus).

Threats
Water withdrawals as a result of population growth and agricultural activities, leads to the loss of critical habitat in this water-poor environment. Overgrazing, introduced species (e.g., cichlid Hemichromis guttatus and the crayfish Procambarus clarkii), potential large-scale tourism, mining, and pollution also threaten many freshwater communities.

Resources
• NationalGeographic.com