Underlying mechanisms maintain diversity while increasing susceptibility to invasion?

"In an ecosystem where lynxes prey on hares, a growing lynx population eventually overhunts and crashes the hare population, which then results in food scarcity and the decline of lynxes, which allows hares to recover, and so on. 

"The researchers wondered if this model could also explain their fluctuating microbial ecosystems.

"When they ran a version of a Lotka-Volterra model modified to introduce an outside species to the community, they found that population fluctuations made the more diverse communities more likely to be invaded. 

"To be able to replicate their surprising results within a simple, time-tested model was comforting, Gore said. 'It’s telling you that you don’t need to invoke additional weird mechanisms' to explain how their microbes behaved, he said. 'It may be a surprising emergent property of these complex dynamical systems.'

"However, those dynamics may not operate equally everywhere. For example, Levine, who mainly studies plant ecosystems, doubts that the rapid population fluctuations found in Gore’s microbes play a major role in ecosystems such as forests or grasslands, which are dominated by organisms such as trees and perennial grasses that can live for decades. But he thinks they could be influential in communities where generations are shorter, such as those of insects or plankton.

"A next step, Levine said, could be to examine what lies beneath the population swings Gore’s team observed. Those fluctuations, he said, are driven by as-yet unknown interactions between species or with their environment. Teasing out exactly how those underlying mechanisms maintain diversity while increasing susceptibility to invasion, Levine said, 'would be fascinating'."