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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

174: Upper Usumacinta

Major Habitat Type:

tropical and subtropical upland 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:

The upper Usumacinta ecoregion lies within eastern Chiapas and southeastern Tabasco within Mexico, and northwestern Guatemala. It covers the upper Usumacinta basin above the confluence with the San Pedro River near the town of Multé.

Drainages flowing into:

The Usumacinta drains into the Gulf of Mexico.

Main rivers or other water bodies:

Tributaries to the Usumacinta include the Lacanjá, Pasión, Chixoy (Salinas), Lacantún, and Tzaconeja rivers.

Topography:

The western part of the ecoregion is bounded by the rugged Sierra Madre de Chiapas in Mexico, and Sierra de los Cuchumatanes in Guatemala. Along the eastern edge of the ecoregion lie the western slopes of the Maya Mountains in Guatemala. The center and northern part of the ecoregion lie at lower elevations, sloping toward the Gulf of Mexico in the north.

Climate:

The ecoregion experiences a tropical climate, with total annual precipitation that exceeds 2100 mm on average.  The mean annual temperature is 23 ºC, with the mean minimum and maximum temperatures around 15 ºC and 31 ºC, respectively.

Freshwater habitats:

Freshwater habitats in this ecoregion include mountain streams, lowland rivers, periodically flooded wetlands, springs, cenotes, and freshwater lagoons. In many areas, especially within the expansive Montes Azules Biosphere Reserve of Mexico, aquatic habitats are surrounded by relatively pristine moist forests. 

Terrestrial Habitats:

The terrestrial habitats are dominated by Petén-Veracruz moist forests at lower elevations and pine-oak forests and montane forests at higher elevations.

Fish Fauna:

The ecoregion harbors over sixty species, a majority of which are in the Poeciliidae, Cichlidae, and Characidae families. Some of the primary fishes include the near-endemic Bramocharax baileyi and B. dorioni. Some euryhaline species include the near-endemic white cichlid (Vieja argentea), Usumacinta cichlid (V. ufermanni), and Grijalva studfish (Xenodexia ctenolepis).

Description of endemic fishes:

Lacantuniidae, represented by the Chiapas catfish (Lacantunia enigmatica), is endemic to the Usumacinta drainage in both the Upper Usumacinta and Grijalva-Usumacinta [173] ecoregions. Other near-endemics include Scolichthys greenwayi, S. iota, Grijalva studfish (Xenodexia ctenolepis), Heterandria attenuata, H. dirempta, H. cataractae, and H. oblique, Amphilophus nourissati, ‘Cichlasoma grammodes’, ‘C.’ ufermanni, Theraps lentiginosus, Thorichthys pasionis, Vieja bifasciata, and V. heterospila. Many of these are restricted to tributaries in Guatemala.

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.

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.

References/sources:

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

Miller, R. R., Minckley, W. L., et al. (2005). "Fishes of México" Chicago Univ. Press.

Miller, R. R., Minckley, W. L., et al. (2005). "Fishes of México" Chicago Univ. Press.

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.

Rodiles-Hernández, R., Pardo, E. Díaz, et al. (1999). "Patterns in the species diversity and composition of the fish community of the Lacanjá River, Chiapas, Mexico" J. Freshwater Ecol. 14(4) 455 - 468.

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