Ecogeographic Regions of Guatemala
Guatemala was divided into eight natural regions or biotic areas by Stuart (1943b, 1957); subsequently some of these were considered to be districts (Stuart, 1964). Originally, these areas were devised on the basis of the salamander fauna. Campbell and Vannini (1989) modified Stuart's regions on the basis of all species of amphibians and reptiles occurring in that country. These region have been further divided below and are useful in describing the distributions of the herpetofauna of Guatemala.
Petén Area. This region encompasses the northern portion of Guatemala, most of Belize, and the lower Polochic and Motagua valleys. This area lies below 600 m and is the largest faunal area in Guatemala. At one time most of the Petén area was heavily forested; that portion lying roughly south of Lake Petén Itzá is tropical humid forest, to the north the terrain is covered with tropical dry forest. As reflected by the vegetation, there is a clinal increase of rainfall from north to south. For the most part, the species characterizing the Petén area are widespread in the Mexican and Central American Caribbean lowlands, and there are few endemic species in this region, although Rhadinaea anachoreta is known from only the type-locality near Laguna Yaxhá. Some relatively dry habitats extend as isolated grassland savannas across northern and central El Petén (map).
Mayan Area. The Maya Mountains of Belize and east-central El Petén contain several peaks that exceed 1,000 m. The windward side of the Maya Mountains is covered with wet forest and contains a herpetological assemblage with many similarities to that of the adjacent lowlands and the southern portion of El Petén. Few endemics occur in this forest, but at least one frog (Rana juliani) appears to be limited to the Maya Mountains. The leeward side of these mountains tends to be much drier and is covered with what has been referred to as pine (Pinus caribaea) parkland or palm (Orbignya cohune) and pine savanna (map).
Cuchumatan Area. This area encompasses most of the northwestern Guatemalan highlands. The Cuchumatan area extends over a considerable area above 2,000 m, and the Sierra de los Cuchumatanes is the most extensive highland region in Middle America with some 1,500 km2 lying above 3,000 m elevation. Most of the Cuchumatan area is covered with lower montane and montane humid forest consisting mainly of pines and oaks. However, in the higher windswept slopes and peaks lower montane wet forest is present and in the extreme northern portion of the Sierra de los Cuchumatanes a spectacular subtropical pluvial forest covers the landscape. In this latter forest, over 6,000 mm of rainfall is received annually. The Cuchumatan area contains numerous endemic species, particularly amphibians, including many species of salamanders (Bolitoglossa jacksoni, Dendrotriton cuchumatanus) and the frogs (Hyla dendrophantasma, Plectrohyla tecunumani and Hyla perkinsi), but shares much of its fauna with the Cuilcan, Chimaltenangan, and Minan Areas (map).
Quecchian Area. Many mountain ranges make up this physiographically complex region which extends from about the level of Purulhá, Baja Verapaz, northward to the Sierra de Chamá, eastward through the Sierra de Santa Cruz, and westward to the deeply entrenched Río Chixoy. This region is covered principally by montane forests that include subtropical wet forest, lower montane wet forest or cloud forest, and subtropical humid forest. Elevations exceed 2,100 m in some of the ranges and rainfall along the windward slopes may exceed 5,000 mm annually. Species characterizing this area include many salamanders, leptodactylid and hylid frogs, lizards of the genera Abronia, Norops, and Xenosaurus, and many snakes. This area shares much of its herpetofauna with the Sierran Area (map).
Chuacús Area. This area included the Sierra de Chuacús that trends extend east-west through central Guatemala, Surprisingly, the Sierra de Chuacús, which has had relatively easy access for the longest period of time, probably remains the most poorly known herpetologically. Unfortunately, it also has suffered greatly from human disturbance. The main crest of the Sierra de Chuacús extends unbroken above 2,100 m for over 50 km. This range narrows and barely exceeds 1,500 m in its eastern portion to the south of the Salamá Basin. Its vegetation is principally lower montane humid forest and consists largely of pines and oaks (Quercus sp.)(map).
Minan Area. This region includes the Sierra de las Minas. The crest of this range extends for about 50 km above 2,100 m, but peaks attain higher elevations than those in the Sierra de Chuacús; Cerro Pinalón and Cerro Raxón are about 3,000 m. Lower montane humid forest covers the leeward (south) side of this range. Near the crest and on the upper portion of the windward (north) side cloud forest prevails. On the lower northern slopes subhumid wet forest is present. Some of the endemics species that have been discovered in this range include Cryptotriton veraepacis, Eleutherodactylus daryi, Abronia gaiophantasma, and Chapinophis xanthocheilus. The herpetofauna of the Minan area shares many species with the Quecchian area (map).
Merendón Area. The Sierra de Merendón (sometimes referred to as the Sierra de Espíritu Santo along its southern terminus) of eastern Guatemala possesses several ridges that lie between 1,000 m and 1,600 m. The upper slopes are covered with subtropical wet forest (for a consideration of life zones, see Holdridge, 1964) and cloud forest conditions prevail on the highest ridges. The Sierra de Merendón is isolated from other highland mesic forests in Guatemala by the Motagua River. Although the portion of this mountain system entering Guatemala is quite small, nevertheless a number of species of the Guatemalan herpetofauna are known in Guatemala only from this range. For example, Cryptotriton wakei, Duellmanohyla soralia, Diploglossus montanus, and Bothriechis thalassinus occur there (map).
Mican Area. The Montañas del Mico in eastern Guatemala are a small isolated range lying to the northeast of the Sierra de las Minas. The Montañas del Mico do not attain a high elevation; Cerro San Gil is the highest peak at 1,267 m. In spite of this relatively low elevation, cloud forest-like conditions are present in the Montañas del Mico, and species sometimes considered indicators such as tree ferns (Cyatheaceae) and emerald toucanets (Aulacorhynchus prasinus) descend almost to sea level. Many species of amphibians and reptiles in the Montañas del Mico are shared with the adjacent mesic lowlands and/or the eastern portion of the Sierra de las Minas (e.g., Ptychohyla panchoi, Amastridium veliferum, and Hydromorphus concolor). However, several species of frogs of the genus Eleutherodactylus appear to be endemic to these mountains (e.g., E. aphanus)(map).
Grijalvan Area. The upper tributaries of the Río Grijalva in western Guatemala including the Río Lagartero, Río Selegua, and Río Cuilco provide important dispersal routes for some dry-land inhabitants such as Cnemidophorus deppii, Heloderma horridum, and Crotalus durissus. These interior valleys form the western part of Stuart's Subhumid Corridor (Stuart, 1954b)(map).
Cuilcan Area. The Montañas de Cuilco are isolated in western Guatemala by the deep entrenchments of the upper tributaries of the Río Grijalva. This range attains elevations of about 3000 m and is covered with pine-oak forest at moderate to high elevations. It shares faunal similarities with the Cuchumatan and Chimaltenangan Areas (map).
Salaman Area. The upper Río Chixoy Valley and associated Salamá Basin (see Schmidt and Stuart, 1941, for description) are interior valleys that form the central portion of Stuart's Subhumid Corridor (Stuart, 1954b), and have been an important dispersal route for some dry-land inhabitants. Most of the area is below 1200 m, however, dry conditions are prevalent the Río Chixoy Valley and Salamá Basin to elevations exceeding 1,500 m (map).
Zacapan Area. This region includes the middle and upper Río Motagua Valley and associated tributaries in the Zacapan area. These interior valleys form the eastern portion of Stuart's Subhumid Corridor (Stuart, 1954b), and have been an important dispersal corridors for certain species. The eastern portion of the Jalapan area, which is contiguous with part of this subhumid corridor, is xeric and effectively provides a dispersal route by which many species gained access into the Motagua Valley from the subhumid Pacific coast (Escuintlan area). Reptiles that apparently have used this avenue to disperse include Rhinoclemmys pulcherrima, Heloderma horridum, Loxocemus bicolor, and Porthidium ophryomegas. Elevations in these dry interior valleys tend to be low, usually ranging from about 100 m to 1,000 m. Along rivers a gallery forest occurs predominated by Salix. The tropical arid and subtropical dry forest vegetation on the floor and lower slopes of these valleys consists of deciduous trees, columnar cactus, and often grassy plains. At slightly higher elevations oaks and pines become interspersed with various species of deciduous trees characteristic of the lower slopes. Additional herpetofaunal elements listed by Stuart (1945b) as typical of this area include Ctenosaura palearis. Sceloporus squamosus, Sceloporus variabilis, Cnemidophorus motaguae, and Leptodeira annulata (map).
Chimaltenangan Area. The Chimaltenangan subarea includes the region west of Guatemala City and south of the headwaters of the Río Cuilco and the Sierra de Chuacús. Many peaks and ridges in this area extends above 2,000 m. Most of the Chimaltenangan area is covered with lower montane and montane humid forest consisting mainly of pines and oaks. A few endemic species are present in the Chimaltenangan Area such as the snake Adelphicos ibarrorum, but the region shares much of its fauna with the Cuchumatan, Fuegan, and Cuilcan Areas (map).
Jalapan Area. This area sometimes has been considered part of the Chimaltenangan subarea. However, the highlands in southeastern Guatemala are not nearly as extensive as, nor do they attain the elevations of, the highlands to the west. A reasonably distinct break between these two highland regions is provided by the Las Vacas Valley in which Guatemala City is located. The Jalapan Area is a land of distinct contrasts, including isolated high peaks covered with lower montane humid forest and subtropical humid or wet forests. Most of these montane forests restricted to the western portion of this area. To the east most of the terrain lies at relatively low elevations and is covered with subtropical or tropical dry forest. This subhumid region has served as a dispersal route for and contains many species adapted to dry conditions. Only a few endemics occur in this area, most notably Pseudoeurycea exspectata Adelphicos daryi, and these are restricted to the higher elevations (map).
Fuegan Area. As is characteristic of piedmonts and regions where highland areas arise abruptly from adjacent lowlands, the Fuegan area receives abundant rainfall. This area is composed of south-facing volcanic slopes and ridges, extending from the Mexican border through south-central Guatemala to past Escuintla. At the lower elevations subtropical wet forest prevails, whereas at high elevations lower montane wet forest is encountered. Elevationally, this area extends from about 600 m to the tree line (at about 3,500 m) on the higher volcanoes. Rainfall is highest in the western portion of this region. A number of wet-forest-adapted species are shared between this area and the wet forests of the Atlantic drainages. However, a moderate number of species are restricted to the Fuegan area, including many species of salamanders, several members of the frog genera Eleutherodactylus and Plectrohyla, the toad Bufo tacanensis, several lizards of the genus Norops, the snake Geophis immaculatus, several other colubrid snakes of the genera Rhadinaea and Tantilla, and the pitviper Bothriechis bicolor (map).
Escuintlan Area. This area lies below 600 m and extends from the Mexican border in the west to El Salvador in the east. Similar to the Fuegan area, the Escuintlan area receives more precipitation in the west than in the east. Two major types of forest are present: tropical humid forest extends as a wide band adjacent to and parallel with the Fuegan area, and tropical dry forest covers the more coastal areas and is contiguous with the Jalapan area in the east. No species are endemic to this area, most being widespread lowland forms occurring also in the adjacent lowlands of western Middle America and the Caribbean. Other species have vertical distributions that extend well into the Fuegan area. Species that are restricted to the area in Guatemala, but that range to the north or south, include Gastrophryne usta, Staurotypus salvinii, Caiman crocodilus, and Ungaliophis continentalis (map).