GRADUATE STUDENTS

Julissa Rojas-Sandoval

by Suzanna Engman

Doctoral student Julissa Rojas-Sandoval is studying an endangered cactus, Harrisia portoricensis, endemic to Mona and nearby Desecheo and Monito islands.

What are the dynamics that cause a plant species to decline? Sometimes the answer is easily discernible—habitat loss, for example. Other times the answer is more complex, involving climate change, insect predation, disease, and other factors. Doctoral student Julissa Rojas-Sandoval is studying an endangered cactus, Harrisia portoricensis, endemic to Mona and nearby Desecheo and Monito islands, and the answer is proving to be complex.

First, Rojas-Sandoval must find, identify, and map individual cacti. She does this with the help of GPS. She also gathers data from their reproductive phenology, counting the number of flowers and fruits. From her data she is able to determine the time period involved in fruit production and the plant requirements during reproductive periods. She also examines the cacti and records their state of health. She has observed that some seem to be suffering from infected lesions stimulated by insects that eat holes in the stems, which later become infected by fungi and bacteria.

In the second stage of her research, she will gather samples at Mona Island and then analyze the lesions—looking for bacteria, fungus and larva—at the Tropical Ecology and Evolution Laboratory at the University of Puerto Rico, Río Piedras. Rojas-Sandoval acknowledges that she has a long way to go to complete her dissertation. “We have big holes in knowledge of this cactus. We don’t know the pollinators, how seeds are dispersed, the consumers of the cactus fruit, the soil conditions it grows best in, and other factors that affect population,” she says. She hopes that her dissertation will supply the answers to these questions and data that can be applied to a management strategy to stop the extinction of this species.

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