BENGALURU: One of the world’s worst invasive plant species - Lantana camara - is here to stay, thanks to its spread by avians. Researchers now say it cannot be eradicated totally but can be controlled at the local level.
A team of Indian ecologists have found that its complete eradication is going to be much harder than previously thought. In fact, removing lantana poses a major challenge in the Indian landscape owing to its easy dispersal by fruit-eating birds.
Researchers from the Nature Conservation Foundation, Wildlife Institute of India, Jawaharlal Nehru University, Indian Institute of Science and CSIRO Land and Water, Australia, have jointly conducted this study.
A systematic study of Lantana’s growth was undertaken in two protected areas — BRT Tiger Reserve, Karnataka, and Rajaji National Park, Uttarakhand, where forest personnel manage Lantana invasion.
Knowing that its plants bear fleshy fruits, which attract fruit-eating birds to disperse the seeds, they then proceeded to examine if birds could fly the distance needed to disperse the Lantana seeds from an area where it grows, to an area where it has been removed.
Through long hours of observation, the team counted the different species of birds that visited Lantana bushes and those that ate its fruit. Bulbuls were found to spend the longest time on bushes and consumed a relatively large number of fruits. The researchers then fed a single Bulbul bird with Lantana fruit for a period of time and measured the time the seeds took to pass through the bird’s gut.
The team further tagged two fruit-eating species of birds commonly found among Lantana bushes with radio collars — a red-vented Bulbul and two red whiskered Bulbuls.
Combining the readings from observed data and computer based modeling, they calculated if birds could indeed pass the seeds to distances sufficient to recolonise areas where Lantana had been removed.
Researchers say, “About half the number of seeds eaten by the Bulbuls could be carried to a distance of 30.2 meters while a majority of the seeds were displaced within a distance of 170 mts from the source plant. Finally, the data showed that birds could indeed carry the seeds from the source plant to managed areas where they could recolonise the source plant.”
Researchers feel that Lantana population should be locally controlled rather than eradicating it totally. “This would be a more realistic goal,” says Geetha Ramaswami, one of the authors of the study. She adds, “To ensure control of Lantana, one needs to account for how far it gets dispersed, and continue management action for as long as source plants and their dispersers exist.”