Ecologists Solve Biodiversity Puzzle

UCSB’s Jonathan Levine claims to have put the last doubts to rest in a long-standing ecological debate with the result of a study, by himself and colleague Dr. Janneke Hille Ris Lambers, proving that niche differences are the key to biodiversity. “Our study provided some of the first field-based evidence that niche differences were truly driving species diversity, resolving a big controversy in ecology,” said Levine, an associate professor in the Department of Ecology, Evolution, and Marine Biology at UCSB.

The study, published August 12 in the journal Nature, was inspired by a “century-old biodiversity puzzle,” according to Levine. Ecologists had not found definitive evidence explaining how different species are able co-exist without all the lesser equipped competition being overtaken by the strongest competitor. Ecologists had pondered what allowed different species to survive in the same environment, when they are tapping into the same pool of resources, but their theories lacked the support of evidence from the field. Ecologists were focused on two main theories: Either species are able to co-exist because niche differences allow them to share an environment and its resources, or they are so equally suited to their environment that no one species is able to topple the competition. When the latter theory was posed about 10 years ago, said Levine, “there was little evidence from the field to support the classic niche ideas. Our study changed this.” The niche theory was assumed to be correct based on mathematical models, Levine said, but until this study it had never actually been tested, either in the lab or out in the field.

The study, conducted in the San Rafael mountains, simulated the elimination of niche differences within experimental communities of annual plants, and watched as species diversity declined quickly in the face of the change. According to Levine, this is the most telling evidence ever provided for the theory that niche differences are key in biodiversity. Examples of these niche differences can be found in many places in nature, including Santa Barbara’s own backyard. “[One] can turn to local oak savannas, where large oak trees with deep roots co-occur with short annual grasses. But how all the different types of annual grasses co-occur is bit of mystery, and could result from each of the species being roughly equal competitors,” Levine said. “Alternatively, less obvious niche differences might control their abundance too, like differences in rooting depth or the seasonality of their growth.” Although the study was conducted mainly for the advancement of pure science, Levine added, it is also true that understanding biodiversity will play a pivotal role in its conservation. The loss of biodiversity in plant systems is extremely detrimental to humans, he said, and this study sheds light on how biodiversity can be preserved.