Ecoregion Description

173: Grijalva - Usumacinta

Major Habitat Type:

tropical and subtropical coastal rivers

Author:

Salvador Contreras Balderas, William Bussing. Additional text was modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment. Island Press, Washington,

Reviewers:

Allison Pease, Texas A&M University, Dept. of Wildlife & Fisheries Sciences

Countries:

Guatemala; Mexico

Boundaries:

This ecoregion is bordered by the Sierra Madre del Sur in the west and the Gulf of México in the north. It extends across the Mexican states of Tabasco, Chiapas, and Campeche, as well as small parts of Veracruz and Oaxaca. Two disjunct areas, including the southern tip of the ecoregion, cross into Guatemala. The boundaries of this ecoregion are largely defined by the watersheds of the Grijalva and lower Usumacinta rivers and their tributaries and the watersheds of the Laguna de Términos and Río Champotón.

Drainages flowing into:

The Grijalva and Usumacinta rivers lie north of the Continental Divide and drain into the Gulf of Mexico.

Main rivers or other water bodies:

This region is composed of the large rivers Grijalva and Usumacinta, plus small basins like Río San Pedro y San Pablo, Laguna de Términos and its drainages, and Río Champotón.

Topography:

The topography of the ecoregion is characterized by high mountains along the Sierra Madre de Chiapas in the southwest, flat coastal plains in the northeast, and the flats of the southern Yucatán Peninsula to Alta Vera Paz in Guatemala.

Climate:

This ecoregion has a tropical climate with a pronounced dry season. The mean annual temperature is 24 ºC. Maximum summer temperatures are around 33 ºC on average, whereas mean minimum winter temperatures average 15 ºC. Total annual precipitation is roughly 1700 mm.

Freshwater habitats:

The Grijalva-Usumacinta ecoregion is characterized by a wide variety of different water habitats. It has fairly extensive riparian habitats, huge expanses of wetlands, mountain creeks, springs, canyon pools, coastal plain rivers, freshwater and brackish lagoons, and even endorheic basins. Freshwater habitats in the ecoregion include mountain creeks, springs, canyon pools, coastal plain rivers, freshwater and brackish lagoons, and swamps. The Pantanos de Centla lies at the delta of the Grijalva and Usumacinta rivers, and includes seasonal flooded forests and wetlands.

Terrestrial Habitats:

Terrestrial habitats in the ecoregion range from the lowland Petén-Veracruz forests and Yucatán moist forests to montane moist forests, dry forests, and pine-oak forests of the Sierra Madre de Chiapas and Chiapas Plateau. The ecoregion also includes riparian habitats and wetlands of the Pantanos de Centla around Laguna de Términos.

Fish Fauna:

The ecoregion contains highly speciose genera. Some of these, such as Profundulus, Theraps, Thorichthys and Vieja, have diversified widely in the ecoregion.

Description of endemic fishes:

Endemic fishes include Rhamdia laluchensis, Olmec blind catfish (R. macuspanensis), widemouth gambusia (Gambusia eurystoma), Grijalva gambusia (Heterophallus milleri), sulphur molly (Poecilia sulphuraria), Upper Grijalva livebearer (Poeciliopsis hnilickai), Palenque priapella (Priapella compressa), Chiapas swordtail (Xiphophorus alvarezi), Chiapas killifish (Profundulus hildebrandi), Theraps coeruleus, Chiapas cichlid (Thorichthys socolofi), Angostura cichlid (Vieja breidohri), tailbar cichlid (V. hartwegi), and the Pantano cichlid (Herichthys pearsei), and Cichlasoma grammodes.

Many species are endemic to the larger Usumacinta drainage, especially the poeciliids Carlhubbsia kidderi, Heterandria attenuata, H. cataractae, H. dirempta, H. obliqua, Scolichthys greenwayi, S. iota, Xenodexia ctenolepis, Xiphophorus alvarezi, and X. signum; and cichlids Amphilophus nourissati, ‘Cichlasoma grammodes’, ‘C.’ ufermanni, Theraps lentiginosus, Thorichthys pasionis, Vieja bifasciata, and V. heterospila.

Other noteworthy fishes:

The Usumacinta endemic poeciliids Scolichthys greenwayi, S. iota and Xenodexia ctenolepis, and the characid Bramocharax baileyi appear to represent relict populations, the former which may have a close relationship to South American poeciliids. The Mayan tetra (Hyphessobrycon compressus) is the northernmost species of this large South American genus.

Evolutionary phenomena:

Poeciliids and cichlids show high adaptive radiation within coastal plain rivers. Fragmentation has also contributed to divergence and endemism.

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 combines a high number of species as well as high endemism. Although Papaloapan [171], Coatzacoalcos [172], and Usumacinta [173, 174] share genera or lower level complexes, the species are endemic and distinctive for each basin. For example, the series of Priapella, Atherinella, Theraps, and Thorichthys justify the distinction of these basins as separate ecoregions.

Level of taxonomic exploration:

Poor, especially in the middle and high regions, where most tributaries have not been explored. 

References/sources:

Abell, R. A., Olson, D. M., et al. (2000). "Freshwater Ecoregions of North America: A Conservation Assessment" Washington, DC, USA: Island Press.

Barrientos-Medina, R. C. (2004)"Diversidad de Mojarras (Teleostei: Cichlidae) en el suroeste de Campeche, México" In Lozano-Vilano, M.L.;Contreras-Balderas, A.J. (Ed.). Libro Homenaje al Dr. Andrés Reséndez-Medina. (pp. 735-250) Monterrey, México: UANL.

Contreras-Balderas, S.,Rivera-Teillery, R. (1983). "Bramocharax (Catemaco) caballero subgén. Et sp. nv., del Lago de Catemaco, Veracruz, México" Publ. Biol.. U.A.N.L., Méx. 1 7-29.

Doadrio, I. (1994). "Freshwater fish fauna of North Africa and its biogeography" Annales du Musée Royal de l'Afrique Centrale, Zoologique 275 21-34.

Doadrio, I., Carmona, J. A., et al. (1999). "Genetic variation and taxonomic análisis of the subgenus Profundulus" J. Fish Biol. 55 751-766.

Lozano-Vilano, M. L.,Contreras-Balderas, S. (1987). "Lista zoogeográfica y ecológica de la ictiofauna continental de Chiapas, México" Southwest. Nat. 32(2) 22-236.

Lozano-Vilano, M. L.,Contreras-Balderas, S. (1990). "Astyanax armandoi, n. sp. From Chiapas, México (Pisces, Ostariophysi: Characidae) with a comparison to the nominal species A. aeneus and A. mexicanus" Universidad y Ciencia (Méx.) 7(14) 95-107.

Rodiles-Hernández, R., Hendrickson, D. A., et al. (2005). "Lacantunia enigmatica (Teleostei: Siluriformes): a new and phyllogenetically puzzling freshwater fish from Mesoamerica" Zootaxa 1000 1-24.

Rosen, D. E. (1970). "A new tetragonopterine characid fish from Guatemala" Am. Mus. Novit. 2435 1-17.

Rosen, D. E. (1979). "Fishes from the uplands and intermontane basins of Guatemala: Revisionary studies and comparative geography" Bull. Amer. Mus. Nat. Hist 162 267-376.

Rosen, D. E. (1972). "Origin of the characid fish genus Bramocharax and a description of a second, more primitive, species in Guatemala" Am. Mus.Novit. 2500 1-21.