Flora Mesoamericana, the first major regional flora ever written in Spanish, is a collaborative effort of the Missouri Botanical Garden, the National Autonomous University of Mexico (UNAM), and the Natural History Museum in London. The Flora describes, for the first time, all the vascular plants growing in the five southernmost states of Mexico (including the Yucatán Peninsula) and all the Central American republics. The first volume of Flora Mesoamericana was published by the UNAM in early 1994 and the latest by the Missouri Botanical Garden.

Hundreds of botanists specializing in tropical taxonomy from around the world are collaborating on the Flora, an extraordinarily important project for botany and for the cooperating institutions.

A total of 11 volumes are planned. All the information is being entered into Tropicos®, the massive botanical database of the Missouri Botanical Garden. The first volumes published are Volume 6 (grasses, sedges, bromeliads, and 25 smaller families of monocots), Volume 4.1 (milk weeds, cucurbits, melastomes, and 30 other smaller families), and Volume 1 (ferns and fern allies). The fern volume is the largest fern flora ever published. Volume 4.2 (coffee, mint, and nine other families) is in press and scheduled for publication in early 2012. The Flora Mesoamericana (http://www.tropicos.org/Project/FM) as of January 2012 provides detailed information on more than 10,000 species.

“Regional flora projects can more accurately reflect natural patterns of plant distribution than projects restricted to a single country,” says Gerrit Davidse, John S. Lehmann Curator of Grasses at the Garden and co-organizer of the project. “Plants pay no attention to political borders.” Davidse coordinates the U.S. effort on the project, which has received its primary funding from the National Science Foundation and The Taylor Fund for Ecological Research. “The Flora is an indispensable and authoritative reference for botanists, ecologists, foresters, horticulturists, agronomists, students, and anyone else interested in the rich diversity of Mesoamerican plants.”

The Mesoamerican region described in Flora Mesoamericana is extremely diverse and interesting. It includes not only rain forests, but also dry forests, alpine areas, and grasslands. Researchers estimate that 18,000 plant species occur in the 800,000-square-kilometer region. The project involves intensive plant collecting as well as writing and editing. Previously published data has been reviewed and synthesized with abundant newly discovered information. In the 20 years since the formal initiation of the project, two new plant families, over a dozen new genera, and hundreds of new species have been described.

One of the most interesting discoveries of the project involves a tiny threadlike plant from southern Mexico. Discovered by Esteban Martínez of UNAM, this plant turned out to be absolutely unique among the quarter-million plant species known to science. Named Lancandonia schismatica and classified in its own family by its discoverer, it is the only plant ever discovered in which the orientation of the sex organs is reversed: the stamens rise within several rings of pistils.

Another new family that was discovered and described by Costa Rican botanists Gómez-Laurito and Gómez during the early years of the Flora Mesoamericana project is Ticodendraceae, a family consisting only of the single species of the genus Ticodendron. A tree with alder-like leaves, it has been found throughout the length of the Mesoamerican region. Haptanthus, found only in one place of now destroyed forest in Honduras, was originally published as a new genus. Recent molecular work has now established that it belongs to the small family Buxaceae.

During their botanical investigations, botanists Barry Hammel and Nelson Zamora described Ruptiliocarpon caracolito, a new genus and species of tree in Costa Rica, and classified it in a plant family that was previously thought to occur only in Africa. The discovery of the relationship between these two groups of plants has led Garden scientists and associates to conclude that they both have descended from an ancestor that was probably present in both Africa and South America when the two continents were much closer together, between 100 and 50 million years ago.

Included in the latest Volume 4.2 are 23 new species scientifically named and described for the first time during the year 2011, so it is absolutely certain that the discovery part of the process is still very active for this part of the world.

“These discoveries are absolutely sensational botanically and unprecedented for any Flora in the world,” says Dr. Peter H. Raven, president emeritus of the Garden. “This project represents a major commitment on the part of the three institutions to studying plants in a region of the world whose flora has been very poorly understood.”

Flora Mesoamericana will provide much useful information about the plants of the region: scientific and common names, technical botanical descriptions, distributions, taxonomic notes and identification keys.