Synchrony is a widespread phenomenon found in many ecological communities, where species’ abundances fluctuate in a positively correlated (synchronous) or negatively correlated (compensatory) manner across time due to underlying drivers such as environmental fluctuations and interspecific competition. However, as an emergent ecological field, the effects of invasion dynamics on synchronous communities have not yet been extensively studied. Therefore, the objective of this research was to determine if the levels of synchrony in a community, and its underlying drivers, alter a community’s resistance and resilience to invasion. We test this by developing a Lotka-Volterra competition model that we adapt from Loreau and de Mazencourt (2013). Using this model, we create a gradient of synchronous to compensatory two-species communities operating under a range of environmental and competition effects. We then simulate the invasion of a third species at different timesteps, to test the initial resistance of the communities. Additionally, we simulate two different levels of invader parameters, testing the underlying effect of invader demography. The model projects community patterns after successful invasions, to demonstrate the level of resilience that synchronous and compensatory communities may have to colonizers.
Results/Conclusions
Across 50 replicates of 500 timesteps each, our model yielded a wide range of dynamics, with variance ratios ranging from 0 (compensatory) to 2 (highly synchronous) across parameter combinations. In our model, as species’ responses to environmental fluctuations increases, synchrony increases; conversely, as the degree of competition increases, so does compensation. Furthermore, we determined that synchronous communities are more adept at resisting invasion attempts than compensatory communities, as they were able to resist invasion 18.25% - 89.25% of the time, depending on the invader’s demographic rates. This is possibly due to synchronous high biomass across species. Compensatory communities were occasionally more resistant to invaders with low intrinsic growth rates, but were extremely vulnerable to good invaders, where they were unsuccessful at resistance 100% of the time. Extending from resistance to resiliency, synchronous communities were able to better suppress the population growth of invaders, and were the only communities able to drive both good and bad invaders to extinction. These results highlight that communities can be both resilient or susceptible to invasions at different points in time depending on demographic and environmental factors, and yields key insights into which communities are most at-risk for the establishment of novel species.