by Suzanna Engman

What can humans do to help an endangered species regain a healthy population count? What is the best management strategy to maintain a healthy population? Will invasive species compete with endangered species? If so, should they be eradicated? The answers to these questions are remarkably complex, and scientists are using both traditional scientific techniques and new computer-generated models based on genetic evidence to answer them. The solutions they are coming up with for problems created by humans—land use change, loss of habitat, pollution, invasive species, and climate change—must be tailor-made because each individual species has become endangered for very specific reasons. In Puerto Rico, scientists estimate that there are about 70 legally designated endangered species, most of them of plants, says Professor of Biology Eugenio Santiago-Valentín, Ph.D., who helped to compile the list. The professor is one of the primary investigators for CATEC’s Species Population Management (SPM) area.

“The Caribbean is one of the ten hottest hotspots in the world. It has about 12,000 species of plants, and roughly half of them are endemic to the region. There’s a lot of diversity here, but we face big challenges in terms of conservation. For example, there’s a lot of pressure from human use—development,” says Santiago-Valentín.

CATEC’s SPM area is collecting baseline data necessary to create successful management plans for endangered species. In some cases, they have found that invasive species might even help to restore endangered endemic species populations. For example, a study conducted by graduate student Marcos Caraballo on the effect of africanized european honeybees, an exotic species, on Goetzea elegans, an endangered endemic tree, found that the bees help in tree pollination, and their activity may aid in tree population recovery.

But the solution to population recovery isn’t quite as simple as that.

In order to develop an effective management plan, other factors need to be taken into consideration, such as the maximum distance between trees at which pollination remains feasible. Many of the estimated 100-150 Goetzea elegans trees left on the island grow far apart from each other and on unprotected land. “We have coordinated with the Department of Natural and Environmental Resources (DRNA by its Spanish acronym) to establish new populations of these rare species within DRNA forests or protected areas. Many of these endangered species are not within protected forests. We’re trying to establish self-sustaining populations in protected areas,” says Santiago-Valentín.

Conservation of the Goetzea tree is just one branch of research in which Santiago-Valentín is involved. The roots of his investigative work are in determining the origins of this plant as well as other plant groups in the region. “My main interest is the study of the flora of Puerto Rico and the Caribbean to understand evolution and geographic relationships among plant groups in the Caribbean—how the species on the island are related to continental lineages and species on other islands.” One of the ways to retrace the evolution of a plant is to construct a genealogy, an evolutionary tree, using molecular information. Since the 1990s botanists have used information in the DNA sequences to reconstruct these evolutionary trees.

Through molecular testing, Santiago was able to discern that Goetzea and other Antillean relatives, which were once thought to form the only endemic plant family in the Caribbean, was actually part of the Solanaceae family. This ethnobotanically important family includes the Datura or jimson weed, eggplant, mandrake, deadly nightshade or belladonna, capsicum (jalapeños, ají, paprika, chile pepper, green peppers), potato, tobacco, and tomatoes. It also includes ornamental plants such as petunias and the “yesterday today and tomorrow” plant, featured on the front cover of this issue of Inventio.

“With molecular data we were able to identify the closest continental lineage of Goetzea and its Antillean relatives as South American,” says Santiago-Valentín. “In this case it was a Brazilian genus. Furthermore, additional data from other colleagues have confirmed that the Antillean species also have a relative in Madagascar. The Antilles-South America-Madagascar relationship reflects part of the common history of most continental masses in the southern hemisphere of our planet. Many millions of years ago, these land masses were part of a large continent, known by scientists as Gondwana. Therefore, the original lineage that gave rise to Goetzea and other Antillean, and South American plant species may be relatively old, and had been part of the Gondwanan flora.”

DNA sequence data have been applied to the field of plant classification in the last 15-20 years, and since then it has gone through a revolution. “Morphological data are still necessary to interpret evolution and adaptation, and the combination of both types of datasets—molecules and morphology—allows what scientists call ‘reciprocal illumination.’ At present, plant classification is far from being old, boring, fossilized. It’s becoming exciting with big changes.”

goetzea@yahoo.com

Graduate student Marcos Caraballo’s CATEC-sponsored research found that an exotic species could actually aid in the survival of an endangered species. “This is one of the most complete studies on pollination biology available for any endangered tree in Puerto Rico, and probably for any endangered tree species in the Caribbean,” says Caraballo’s thesis advisor, Eugenio Santiago-Valentín. Caraballo found that the Goetzea elegans requires cross-pollination (pollination from tree to tree) with an experiment in which he covered the flowers with cloth bags to control flower visitation pollinators. He left the bags on when he wasn’t there then unbagged them when he returned to observe the flowers with binoculars and a spotting scope. He identified the two primary pollinators of the tree—the native bird Coereba flaveola, known locally as the reinita or bananaquit, and the exotic africanized european honeybee—after he performed a series of manipulations to understand the effect of pollen transfer in reproduction. For example, to see if a flower could pollinate itself, he transferred the pollen from the masculine part of the flower to the feminine part and then bagged it. He also eliminated the masculine part of some flowers. Caraballo found that Goetzea exhibit a combination of different reproductive strategies. While some may self-pollinate but reproduce mainly through outcrossing, very few could produce fruits asexually. Caraballo then compared the pollination effectiveness of the birds with the bees and concluded that the native species and the exotic pollinator exhibit similar levels of effective pollination. The results of Caraballo’s study are being used to develop a five-year review of the U.S. Fish & Wildlife plan for several endangered species in Puerto Rico, including Goetzea elegans. Carballo and Santiago-Valentín are advisors for the review and will provide comments on the draft of the recovery plan for the species.