Included here are the forests of the tropical lowlands of Mexico and all other parts of Central America south of Mexico including Guatemala, Honduras, San Salvador, Nicaragua, Costa Rica and much of Panama. Two broad categories of forest have been described but there are probably several other types.

Yucatan Tropical Forest

Until recently these forests were thought to be relatively homogenous, but are now known to comprise several communities depending on soil type, terrain and rainfall levels. In the low rainfall areas on relatively shallow calcareous soils in northern parts of Quintana Roo, the forest exclusive to this zone is characterized by Agave angustifolia, Plumeria obtusa and the Yucatan endemic Sebestiana adenophora (family?). These low stature forests rarely exceed about 7 m but typically have a shrub layer up to 2 m and an herb layer up to 1 m. Other common species include Bromelia karatas, Esenbeckia pentaphylla, Eugenia mayana, Rhoeo discolor and the Yucatan endemics Beaucarnea pliabilis (Ruscaceae), Bourreria pulchra (Boraginaceae), Caesalpinia yucatanensis (Fabaceae) and Trichilia minutiflora (Meliaceae). Where rainfall is slightly higher the forests are characterized by Manilkara zapota and the Yucatan endemic palm Coccothrinax readii (Arecaceae). These forests cover many parts of Quintana Roo and can have canopy trees reaching 30 m or so. Other typical species include Bursera simarouba, Laetia thamnia, Malmea depressa, Neea psychotriodes and the Yucatan endemics Hampea trilobata (Malvaceae) and Ottoschulzia pallida (Icacinaceae).

The under storey consists largely of saplings and climbers, but shrubs such as Abutilon permolla, Byttneria aculeata and Malvaviscum arboreus may be encountered together with herbs such as Anthurium schlechtendalii, Lasiacis divaricata and the endemic Olyra yucatana (Poaceae). With increasing rain dense forests typified by Bursera simaruba and the Yucatan endemics Hampea trilobata (Malvaceae) and Metopium brownei (Anacardiaceae) occur. These forests have a central distribution in Quintana Roo. Common understory species include Casearia nitida, Chamaedorea seifrizii, Lonchocarpus rugosus and Randia aculeate, but a special feature of these forests is the rich arboreal flora with herbaceous species such as Ichnanthus lanceolata and Zamia loddigesii, shrubs such as Malvaviscus arboreus and climbers like Arrabidaea floribunda, Passiflora coriacea and the Yucatan endemic Desmonicus quasillarius (family?). In the highest rainfall areas where annual precipitation exceeds 1400 mm the forests normally have three distinct stories. In south-central Quinttana Roo the characteristic species are Caesalpinia gaumeri and Vitex gaumeri. Other typical species include Byrsonima bucidaefolia, Diospyros verae-crucis, Spondias mombin and the Yucatan endemics Acacia gaumeri (Fabaceae) and Alseis yucatanensis (Rubiaceae). Vitex gaumeri is one of the most abundant trees on the peninsula. In the wettest areas in southern Quintana Roo the dense forest have a well-developed vertical structure with canopy trees reaching heights of up to 30 m. Here the most abundant trees are Brosimum alicastrum, Orbignya cohuna and Trichilia glabra. However, the forests throughout the Yucatan are extremely diverse and contain many of the species endemic to the peninsula. In addition to the ones already mentioned these include Acacia cedilloi (Fabaceae), Coccoloba reflexiflora (Polygonaceae), Croton campechianus (Euphorbiaceae), Cryosophila stauracantha (Arecaceae), Diospyros cuneata (Ebenaceae), Erythroxylum bequaertii (Erythroxylaceae), Exothea diphylla (Sapindaceae), Jatropha gaumeri (Euphorbiaceae), Lonchocarpus xuul (Fabaceae), Platymiscium yucatanum (Fabaceae), Sideroxylon foetidissimum subsp. gaumeri (Sapotaceae) and Thouinia paucidentalis (Sapindaceae).

Costa Rican Tropical Forest

The La Selva Biological Station located where the foothills of Costa Rica’s central volcanic mountains give way the Caribbean coastal plain has compiled detailed descriptions of these forests. They are characterized by irregular canopies ranging in height from 30-55 m and dominated by the endemic Pentaclethra macroloba (Mimosoidaceae). Palms are a distinctive feature of the sub canopy which are made more conspicuous by the long leaves of Welfia georgii, the high stilt roots of Iriartea deltoidea and Socratea exorrhiza, and the long spines of the endemic Astrocaryum confertum (Arecaceae). Typical dicot species of the sub canopy include Dendropanax arboreus, Dystovomita paniculata and the endemic Protium panamensis, P. pittieri (Burseraceae) and Unoniopsis pittieri (Annonaceae). However, below the sub canopy the under storey is more difficult to define, but a story of small trees ranging in height from 5-15 m can often be distinguished. These include Anaxagorea crassipetala, Cassipourea elliptica, Rinorea deflexiflora, Symphonia globulifera and the endemic Guarea rhopalocarpa (Melicaceae). A story that can be broadly described as a shrub layer usually occurs growing to a height of about 5 m. Palms are again characteristic here with species such as Asterogyne martiana and the endemic, multi-stemmed Geonoma congesta (Arecaceae), while common dicots are Carpotroche platyptera, Mabea occidentalis, Miconia simplex and the endemic Herrania purpurea (Sterculiaceae). Tree seedlings and woody lianas rather than herbaceous plants dominate much of the ground layer, but with occasional perennial herbs. These include Asplundia uncinata, Besleria columneoides, Danaea wendlandii and the endemic Calathea cleistantha (Marantaceae) and Spathiphyllum fulvovirens (Araceae). There are a number of other interesting endemic species found in these forests. Pariana parvispica (Poaceae) is a bambusoid grass endemic to the Caribbean lowland forests of Costa Rica, and represents the northernmost example of this South American genus. Zamia skinneri (Zamiaceae) is an endemic under story cycad with no noticeable difference between the sexes.

References

Bijleveld, C. F. A. 1998. The Vegetation of Shipstern Nature Reserve (Corozal District, Belize, Central America). A structural and floristic approach. International Tropical Conservation Foundation.

Clewell, A. E. 1986. Observations on the vegetation of the Mosquitia in Honduras. Sida, 11: 258-270.

D’arcy, W. G. 1987. Flora of Panama. Part 1: The Introduction and Checklist. Missouri Botanical Garden, Saint Louis, Missouri.

Durán, R., Trejo-Torres, J. C. & Ibarra-Manríquez, G. 1998. Endemic phytotaxa of the Peninsula of Yucatán. Harvard Papers in Botany, 3: 265-316.

Frankie, G. W., Baker, H. G. & Opler, P. A. 1974. Comparative phenological studies of trees in tropical wet and dry forests in the lowlands of Costa Rica. Journal of Ecology, 62: 881-919.

Gómez-Pompa, A. 1973. Ecology of the vegetation of Veracruz. In: Vegetation and vegetational history of northern Latin America. Elsevier Scientific Publishing Company.

Hartshorn, G. S. 1989. Tropical and subtropical vegetation of meso-America. In: North American Terrestrial Vegetation. Eds. M. G. Barbour and W. D. Billings. Cambridge University Press.

Janzen, D. H. 1983. Costa Rican Natural History. The University of Chicago Press.

Johnston, I. M. 1931. The flora of the Revillagigedo Islands. Proceedings of the California Academy of Sciences, 20: 9-104.

Leopold, A. S. 1950. Vegetation zones of Mexico. Ecology, 31: 507-518.

Lieberman, D., Lieberman, M., Peralta, P. & Hartshorn, G. S. 1996. Tropical forest structure and composition on a large-scale altitudinal gradient in Costa Rica. Journal of Ecology, 84: 137-152.

Lira, R., Villasenor, J. L. & Ortiz, E. 2002. A proposal for the conservation of the family Cucurbitaceae in Mexico. Biodiversity and Conservation, 11: 1699-1720.

McDade, L. A., Bawa, K. S., Hespenheide, H. A. & Hartshorn, G. S. 1994. Le Selva. Ecology and Natural History of a Neotropical Rain Forest. The University of Chicago Press.

Nee, M. H. & Atha, D. E. 1999. Checklist of the vascular plants of Belize: with common names and uses. Memoirs of the New York Botanical Garden, 85: 1-246.

Ramamoorthy, T. P., Bye, R., Lot, A. & Fa, J. 1993. Biological Diversity in Mexico: Origins and Distribution. Oxford University Press.

Ricketts, T. h. et al. 1999. Terrestrial Ecosystems of North America - a conservation assessment. World Wildlife Fund, USA and Canada. Island Press, Washington.

Sanchez-Sanchez, O. & Islebe, G. A. 2002. Tropical forest communities in southwestern Mexico. Plant Ecology, 158: 183-200.

Sawyer, J. O. & Lindsey, A. A. 1971. Vegetation of life zones in Costa Rica. Indiana Academy of Science, Monograph 2: 1-214.

Seymour, F. C. 1980. A checklist of the vascular plants of Nicaragua 1968-1976. Phytological Memoirs, 1: 1-314.

Standley, P. C. 1928. Flora of the Panama Canal zone. Smithsonian Institution United States of America. Contributions from the United States National Herbarium. Volume 27.

Sutherland, C. H. N. 2001. Plantas descritas originalmente de Honduras y sus nomenclaturas equivalentes actuales. Ceiba, 42: 1-71.

Taylor, B. W. 1963. An outline of the vegetation of Nicaragua. Journal of Ecology, 51: 27-54.

Zuchowski, W. 2007. Tropical Plants of Costa Rica. A Zona Tropical Publication from Comstock Publishing Associates.