Pondberry Seed Fate: Animal Dispersers, Animal Predators

Results of research study on the Delta National Forest

Student intern Andreza Martins (l.) and SRS biological science technician Carl Smith (r.) focusing video camera on pondberry plot to record animal visits. Photo by Collin Tidwell.
Student intern Andreza Martins (l.) and SRS biological science technician Carl Smith (r.) focusing video camera on pondberry plot to record animal visits. Photo by Collin Tidwell.

Although pondberry can still be found in nine southern states, it is vanishingly rare. “Pondberry is an endangered species,” says Andreza Martins. “In most states, only one or two populations of the shrub are known to exist.”

Currently a forest engineer in Brazil, Martins interned at the U.S. Forest Service Southern Research Station (SRS) in 2005 and worked with research ecologist Margaret Devall and emeritus wildlife biologist Paul Hamel at the SRS Center for Bottomland Hardwoods Research. Martins and her colleague Fernanda Abilio, who was also a student intern at SRS, are principal authors of a recent study on pondberry published in the journal Global Ecology and Conservation.

Scientists at the SRS Center for Bottomland Hardwoods Research have studied pondberry for more than 15 years. Martins and Abilio worked on the most recent study, which focuses on the birds and mammals that eat pondberry seeds and leaves. Because pondberry is so rare, it is critical for managers and policy makers to understand how it reproduces and is dispersed naturally on the landscape.

Pondberry only grows in seasonally flooded bottomland hardwood forests or on the edges of ponds and wetlands, and this type of habitat is increasingly rare in the southern U.S. due to timber cutting, clearing of land, and local draining or flooding of wetlands. The recent pondberry study took place in the Delta National Forest in Mississippi. The forest is one of the largest remaining bottomland hardwood tracts in the U.S., and is home to about 273 pondberry colonies, making it the largest known pondberry habitat in the world.

Pondberry (Lindera melissifolia) with ripe fruit. Photo by Prisceilla deO. Antonelli.
Pondberry (Lindera melissifolia) with ripe fruit. Photo by Prisceilla deO. Antonelli.

To study behaviors of animals without disturbing them, scientists aimed video cameras at study plots. Each plot was approximately a square yard, and researchers placed pondberry seeds or seedlings in the plots. The video cameras recorded continuously throughout the study period; animals visiting the plots were later identified from the recordings.

Many bird and mammal species were recorded eating pondberry seeds. Scientists paid special attention to how the animals ate pondberry seeds – species that chewed and crushed the seeds were identified as seed predators, while species that ate the fruits without destroying the seeds were identified as seed dispersers because they later release the whole seeds elsewhere on the landscape.

Dispersers included birds like the hermit thrush, while northern cardinals, tufted titmice, and other birds seemed to destroy the seeds when they ate them. Squirrels, swamp rabbits, armadillos, white-tailed deer, and other animals also appeared to damage seeds, but in some cases, these animals may help disperse seeds by forgetfully caching them.

Pondberry has a knack for growing in places that other shrubs can’t, such as periodically flooded forests. The scientists also compared seed survival in plots with low and high cover in the understory. “We found that pondberry seeds are more likely to survive in areas with low cover,” says Devall. “The low cover may limit the numbers of seed and seedling predators.”

Read the full text of the article.

For more information, email Margaret Devall at mdevall@fs.fed.us.

 

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