Ecoregion Description

171: Papaloapan

Major Habitat Type:

tropical and subtropical coastal rivers

Author:

Salvador Contreras Balderas, Universidad Autónoma de Nuevo León. Additional text was modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment

Countries:

Mexico

Boundaries:

This coastal ecoregion encompasses the Río Papaloapan basin, which covers most of central Veracruz, two disjunct portions of eastern Puebla, and part of northern Oaxaca.

Drainages flowing into:

Gulf of Mexico

Main rivers or other water bodies:

The extent of the ecoregion is defined largely by the watershed of the Río Papaloapan and its tributaries that drain into the Gulf of Mexico. Major tributaries include Río Santo Domingo, Río San Juan, and Río Trinidad. There are also tributaries of the Laguna de Alvarado, including Río Blanco, Río Otopa, and some basins like Laguna Mandinga, Laguna de Catemaco, and Presa Miguel Alemán.

Topography:

The headwaters of the Papaloapan rise in the Sierra Madre Oriental in the western part of the ecoregion, and then drain towards the Gulf of Mexico. Elevations in the ecoregion range from sea level to over 3000 m asl. Sierra Madre de Oaxaca lies in the southwest and the Eje Volcánico lies at the northern border.

Climate:

The climate along the coastal plain in the state of Veracruz is tropical wet and dry and tropical monsoon. It experiences heavy but seasonal precipitation that averages 1750 mm annually, but exceeds 3500 mm in some places. The mean annual temperature is 22 ºC, mean minimum temperature is 13 ºC, and mean maximum temperature is 32 ºC.

Freshwater habitats:

Freshwater habitats include headwaters, springs, creeks, lakes, lagoons, falls, rapids, and pools.

In the northeastern part of the ecoregion is Laguna de Catemaco, a volcanic crater lake 335 m above sea level. A number of small streams flow down the interior face of the crater into the lake, which has an outlet to the northeast into a river known locally as the Río Grande. Twelve kilometers downstream of the outflow, a 45-meter high waterfall, the Salto de Eyiplanta, effectively isolates the lake from the lower reaches of the Río Papaloapan system. The lake is extremely turbid due to suspended particles of basaltic dust.

Terrestrial Habitats:

The ecoregion contains a variety of terrestrial ecoregions, including moist forests, dry forests, and mangroves along the coast and pine-oak forests, dry forests, and matorral at higher elevations.

Fish Fauna:

The ecoregion contains nearly sixty species. Poeciliids represent a third of the species in genera such as Xiphophorus, Poecilia, Poeciliopsis, Heterandria, and Priapella.

Description of endemic fishes:

The Papaloapan ecoregion is characterized by relatively high endemism within its ichthyofauna. Around 28 percent of the native fish species are endemic to this region. Endemics include the graceful priapella (Priapella bonita), Olmec priapella (P. olmecae), blindwhiskered catfish (Rhamdia reddelli), and species of Atherinella and Xiphophorus. Also within this ecoregion is Laguna de Catemaco, a remarkable lake with endemic fish such as the Catemaco characin (Bramocharax caballeroi).

Other noteworthy aquatic biotic elements:

The ecoregion contains 27 (26%) endemic aquatic herpetofauna species, such as Anotheca spinosa. Two crayfish also occur here.

Evolutionary phenomena:

There is speciation in the genera Atherinella, Xiphophorus, and cave-dwelling Rhamdia.

This is one of the areas where two forms of Astyanax exist in basically distinct habitats, usually headstreams (A. mexicanus) and low coastal areas (A. aeneus).

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. Although the Papaloapan, Coatzacoalcos, and Usumacinta rivers share genera or lower level species complexes, there are endemic and distinctive species for each basin, like the series of Priapella, Atherinella, Theraps, and Thorichthys. This justified the distinction of each basin as a separate ecoregion.

Level of taxonomic exploration:

Poor along the western mountainous headwaters and also around coastal lagoons, but regular within the middle ranges.

References/sources:

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

Chernoff, B. (1986). "Systematics of American atherinid fishes of the genus Atherinella. I. The subgenus Atherinella" Proc. Acad. Nat. Sci. Phila. 138(1) 86 - 188.

Contreras-Balderas, S., Obregón, H., et al. (1996). "Punta del Morro, an Interesting barrier for distributional patterns of continental fishes in North and Central Veracruz, México" Acta Biol. Ven. 16(4) 37-42.

Hubbs, C. L., Miller, R. R., et al. (1974)"Hydrographic history and relict fishes of the North-Central Great Basin" In Memoirs of the California Academy of Sciences, vol 7.. San Francisco: California Academy of Sciences.

Obregón-Barbosa, H., Contreras-Balderas, S., et al. (1994). "The fishes of Northern and Central Veracruz, México" Hydrobiologia (Belgium) 286 79-95.