Lions, elephants, and giraffes may be relatively minor players when it comes to shaping the African savanna ecosystem. “The real king of the savanna appears to be the termite,” say researchers.
“These humble creatures contribute mightily to grassland productivity in central Kenya via a network of uniformly distributed colonies. Termite mounds greatly enhance plant and animal activity at the local level, while their even distribution over a larger area maximizes ecosystem-wide productivity,” Harvard University says in a news statement about the study, published this week in the journal PLoS Biology.
“Often it’s the small things that matter most.”
The research “affirms a counterintuitive approach to population ecology: Often it’s the small things that matter most,” the university adds.
A soldier Odontotermes termite patrols a bit of fungal comb that has been removed from a mound. “Although these termites spend their lives underground and are rarely seen, their activities support the charismatic biodiversity of African savannas,” says a Harvard study.
Photo courtesy of Public Library of Science
“It’s not always the charismatic predators–animals like lions and leopards–that exert the greatest control on populations,” says Robert M. Pringle, a research fellow at Harvard. “As E.O. Wilson likes to point out, in many respects it’s the little things that run the world. In the case of the savanna, it appears these termites have tremendous influence and are central to the functioning of this ecosystem.”
This satellite photo shows the uniform distribution of termite mounds. Small red regions are indicative of rapid plant growth.
Image provided by Robert M. Pringle
Prior research on the Kenya dwarf gecko initially drew Pringle’s attention to the peculiar role of grassy termite mounds, which in this part of Kenya are some 10 meters in diameter and spaced some 60 to 100 meters apart, Harvard said.
“Each mound teems with millions of termites, who build the mounds over the course of centuries.
“After observing unexpectedly high numbers of lizards in the vicinity of mounds, Pringle and his colleagues began to quantify ecological productivity relative to mound density. They found that each mound supported dense aggregations of flora and fauna: Plants grew more rapidly the closer they were to mounds, and animal populations and reproductive rates fell off appreciably with greater distance.”
This is a soldier termite in a fungal comb. These termites are rarely seen above ground, but their subterranean activities support the productivity and biodiversity of African savannas.
Photo by Robert M. Pringle
What was observed on the ground was even clearer in satellite imagery.
Each mound–relatively inconspicuous on the Kenyan grassland–stood at the center of a burst of floral productivity, Harvard said.
“More importantly, these bursts were highly organized in relation to one another, evenly dispersed as if squares on a checkerboard. The result, says Pringle, is an optimized network of plant and animal output closely tied to the ordered distribution of termite mounds.”
“In essence, the highly regular spatial pattern of fertile mounds generated by termites actually increases overall levels of ecosystem production. And it does so in such a profound way,” says Todd M. Palmer, assistant professor of biology at the University of Florida and an affiliate of the Mpala Research Centre in Nanyuki, Kenya.
“Seen from above, the grid-work of termite mounds in the savanna is not just a pretty picture. The over-dispersion, or regular distribution of these termite mounds, plays an important role in elevating the services this ecosystem provides.”
Termite mounds, seen here in Kenya’s Masai Mara as an oasis of green in a sea of brown, help support savanna biodiversity at all levels, from tiny insects to this family of cheetahs.
Photo by Robert M. Pringle
The mechanism through which termite activity is transformed into far-reaching effects on the ecosystem is a complex one, Harvard said.
“Pringle and Palmer suspect termites import coarse particles into the otherwise fine soil in the vicinity of their mounds. These coarser particles promote water infiltration of the soil, even as they discourage disruptive shrinking and swelling of topsoil in response to precipitation or drought.
“The mounds also show elevated levels of nutrients such as phosphorus and nitrogen. All this beneficial soil alteration appears to directly and indirectly mold ecosystem services far beyond the immediate vicinity of the mound.
“While further studies will explore the mechanism through which these spatial patterns of termite mounds emerge, Pringle and Palmer suggest that the present work has implications beyond the basic questions of ecology.”
“Termites are typically viewed as pests, and as threats to agricultural and livestock production,” Pringle says. “But productivity — of both wild and human-dominated landscapes — may be more intricately tied to the pattern-generating organisms of the larger natural landscape than is commonly understood.”
Implications for conservation
The findings also have important implications for conservation, Palmer says.
“As we think restoring degraded ecosystems, as we think about restoring coral reefs, or restoring plant communities, this over-dispersed pattern is teaching us something,” he says. “It’s saying we might want to think about doing our coral restoration or plant restoration in a way that takes advantage of this ecosystem productivity enhancing phenomenon.”
Pringle and Palmer’s co-authors on the PLoS Biology paper are Daniel F. Doak of the Mpala Research Centre and the University of Wyoming; Alison K. Brody of the Mpala Research Centre and the University of Vermont; and Rudy Jocqué of the Royal Museum for Central Africa in Tervuren, Belgium. Their work was supported by the Sherwood Family Foundation and the National Science Foundation.