Keystone species are organisms that are crucial to an ecosystem’s survival. Although they might not be the most plentiful or largest species in an ecosystem, other species still rely on them to survive. Most often, a keystone species plays a critical role in the food web. If a keystone species is removed, the structure and biodiversity of the ecosystem can change drastically.

The five broad categories of keystone species are predators, prey, ecosystem engineers, mutualists, and plants. Predators keep the population and range of their prey in check, and prey are a critical food source for predators. Ecosystem engineers help define the biodiversity of the habitat by creating, modifying, or maintaining the landscape. Mutualists are two or more species that engage for each other’s benefit, while plants can provide food and shelter to other species.

The longleaf pine ecosystem is home to incredible biodiversity, with approximately 900 unique plant species and over 20 threatened or endangered species. One of those threatened species is the gopher tortoise, which is also a keystone species to the longleaf pine. Other keystone species include the red-cockaded woodpecker, Cooley’s meadowrue, and the eastern indigo snake. (1, 2)

Image by Randy Browning/USFWS from Flickr

Gopher tortoise (Gopherus polyphemus)

Longleaf pine forests make ideal habitats for gopher tortoises because of the abundance of sunlight, grassy forest floors, and sandy soils. The only tortoise naturally found east of the Mississippi River, gopher tortoises grow to an average length of 9 to 11 inches long and can live between 40 and 60 years. Gopher tortoises spend 80% of their lifetime in burrows, using multiple throughout their lives. These burrows are typically 15 feet long and 6.5 feet deep, providing protection from threats like fire and hurricanes, along with protection from the elements. They also maintain a steady temperature and humidity year-round. 350 other species, including mice, snakes, frogs, and small mammals, rely on the burrows dug by the gopher tortoise. (2, 3)

Red-cockaded woodpecker (Picoides borealis)

This territorial, non-migratory species is around 7 inches long, with a 15-inch wingspan. Currently endangered, the red-cockaded woodpecker used to be fairly common in the southeastern U.S., but their ideal habitat of mature pine woods in longleaf pine forests has become scarce due to deforestation. They nest in cavities in older pines (usually over 80 years old) infected with fungus called red heart disease, which makes the inner wood soft. The red-cockaded is the only woodpecker to excavate cavities in living pine trees. These cavities provide spaces for at least 27 species of vertebrates to roost or nest. (4, 5)

Image by James Henderson from Wikimedia Commons

Cooley’s meadowrue (Thalictrum cooleyi)

Native to the southeastern U.S. in Florida, North Carolina, and Georgia, Cooley’s meadowrue is currently endangered due to the destruction and alteration of its habitat by fire suppression. Controlled burns can help species such as Cooley’s meadowrue and the longleaf pine make a comeback. When forests have species such as Cooley’s meadow, there is greater biodiversity, and forests are healthier. Cooley’s meadowrue stems are typically 3.3 feet tall, but can grow up to 6.6 feet tall on recently burned sites. This perennial herb grows in circumneutral soils in wet pine savannas and savanna-like areas. (6, 7)

Eastern indigo snake (Drymarchon couperi)

One of the largest snakes in North America, eastern indigo snakes can reach lengths of 8 feet. Non-venomous, they have blue-ish black colored scales with a white or orange chin and throat. Eastern indigo snakes are currently a threatened species, facing habitat loss from urbanization and fragmentation from housing and road development. As a top predator of the longleaf pine habitat, they help keep the ecosystem healthy and balanced by preventing the overpopulation of other species. They also depend on another keystone species for their own survival as they take shelter in gopher tortoise burrows in the winter. (8, 9)

Citations

(1) Denchak, M. (2019, September 9). Keystone species 101. Natural Resources Defense Council. https://www.nrdc.org/stories/keystone-species-101#whatis

(2) Holewinski, B. (n.d.). Restoring longleaf pine forests and keystone species habitat. National Forest Foundation. https://www.nationalforests.org/blog/restoring-longleaf-pine-forests-and-keystone-species-habitat

(3) Florida Fish And Wildlife Conservation Commission. (n.d.). Gopher tortoise. https://myfwc.com/wildlifehabitats/profiles/reptiles/gopher-tortoise/

(4) U.S. Fish and Wildlife Service. (2020, November 17). Red-cockaded woodpecker recovery. https://www.fws.gov/rcwrecovery/rcw.html

(5) Audubon. (2020, January 13). Red-cockaded woodpecker. https://www.audubon.org/field-guide/bird/red-cockaded-woodpecker

(6) Mansberg, L. (2021, May 13). Cooley's Meadowrue. NatureServe Explorer. https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.137457/Thalictrum_cooleyi

(7) U.S. Fish and Wildlife Service. (2020, November 10). Cooley’s Meadowrue. https://www.fws.gov/raleigh/species/es_cooleys_meadowrue.html

(8) The Orianne Society. (2018, August 30). The eastern indigo snake. https://www.oriannesociety.org/about/the-eastern-indigo-snake/

(9) Florida Fish And Wildlife Conservation Commission. (n.d.). Eastern indigo snake. https://myfwc.com/wildlifehabitats/profiles/reptiles/snakes/eastern-indigo-snake/

Keystone Species Spotlight: Gopher Tortoise, Red-cockaded Woodpecker, Cooley’s Meadowrue, and Eastern Indigo Snake

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