DNA evidence shows endangered Mexican cloud forests need unique protection

February 13th, 2013
Cover

The Azure-crowned hummingbird, Amazilia cyanocephala, is native to cloud forests including those in northern Veracruz, Mexico, pictured here. The forests are among the most threatened habitats worldwide.
Photos by Clementina Gonzalez (bird) and Eduardo Ruiz Sanchez

GAINESVILLE, Fla. — A new study co-authored by University of Florida researchers shows cloud forests in southern Mexico and northern Central America – among the most threatened habitats worldwide – require more specialized conservation than previously believed.

Cloud forests occur in mountainous regions and provide water downstream to towns and regions for healthy functioning of surrounding ecosystems. In northern Mesoamerica, which includes southern Mexico and Guatemala, 50 percent of original cloud forest habitat has been destroyed and it occupies less than 1 percent of the total geographic area today. Using DNA markers and computer programs designed to reconstruct the past, an international team of scientists determined that while populations of plant and animal species endemic to these forests have similar geographic distributions today, they show diverse patterns of genetic differentiation among their populations, reflecting differing past evolutionary histories.

The study published Thursday in PLOS One provides valuable information for developing management strategies for these threatened environments that house unknown biodiversity and numerous endangered native species.

“What this information means from a conservation standpoint is that you can’t pick one cloud forest area and say, ‘I’m just going to preserve what’s here in this one spot,’ ” said study co-author Doug Soltis, a distinguished professor at the Florida Museum of Natural History and UF’s biology department. “To preserve genetic diversity, you really need to conserve areas that represent different belts, or regions of cloud forest.”

Scientists have historically thought of cloud forests as a single habitat unit in northern Mesoamerica. However, genetic data show that endemic species of birds, rodents and plants actually comprise genetically distinct lineages, with different geographic areas home to genetically distinct populations. These differences among populations reflect periods of isolation and different histories of migration over the past several million years during environmental changes, such as glaciations.

In collaboration with colleagues from Mexico, Doug Soltis and Pam Soltis, also a distinguished professor at the Florida Museum of Natural History on the UF campus, conducted DNA analysis on five plant species: two trees, a shrub, a herbaceous plant and one epiphytic, from the group that includes mosses, orchids and bromeliads.

“Geographic breaks in different species at the same places may look like they were all caused by similar environmental factors, but when you add the time component, you can see that they actually occurred at different times,“ Pam Soltis said. “That’s one of the things I think is most fascinating about the results of the study.”

As the name implies, cloud forests are frequently or seasonally covered in clouds or mist. They occur on mountain slopes, where cooler temperatures cause clouds to form. The highlands of northern Mesoamerica are recognized as one of Conservation International’s ‘Biodiversity Hotspots,’ and the wide variety of plants and animals is a surprising contrast to the vast dry, arid plains typically associated with Mexico’s landscape, Doug Soltis said

“Even though we think of most of Mexico as having very dry-adapted organisms, in the cloud forests, you have a lot of very temperate or wet-adapted plants and animals,” Doug Soltis said. “A great example is the tree sweetgum, which we have growing here on the UF campus – it’s down in those cloud forests in southern Mexico even though it’s primarily a temperate plant from the eastern U.S. Beech trees are also there and you think of those as being in the northern United States, maybe in northern North Carolina or Virginia. It’s a very striking place.”

In 2011, study co-authors traveled to Veracruz, Mexico, to conduct phylogenetic analyses on the species in surrounding cloud forests. Researchers used comparative phylogeography, a field of genetics in which scientists collect sample populations and use genetic markers to reconstruct the past. “This is like CSI, but in natural populations,” Doug Soltis said.

Scientists hope these types of studies will help prompt the Mexican government to support conservation of cloud forest habitats in national or regional parks, he said.

“Most of this ecosystem has either been cut down or remains because you can grow coffee in these areas,” Doug Soltis said. “It is now a highly fragmented and damaged habitat that requires immediate protection before it is too late.”

Study co-authors include Juan Francisco Ornelas, Victoria Sosa, Clementina González, Carla Gutiérrez-Rodríguez, Alejandro Espinosa de los Monteros and Eduardo Ruiz-Sanchez of Instituto de Ecología, AC, Xalapa, in Veracruz, Mexico; Juan M. Daza of Universidad de Antioquia in Colombia; Todd A. Castoe of the University of Colorado School of Medicine; and Charles Bell of the University of New Orleans.

-30-

Writer: Danielle Torrent, dtorrent@flmnh.ufl.edu
Sources: Doug Soltis, office: 352-273-1963, dsoltis@botany.ufl.edu; Pam Soltis, office: 352-273-1964, psoltis@flmnh.ufl.edu
Media contact: Paul Ramey, pramey@flmnh.ufl.edu