Analysis of an alternative formulation of the Lotka-Volterra competition model yields new insights into coexistence

Background/Question/Methods

Existing theory suggests that in well-mixed populations competitive coexistence occurs when species inhibit themselves more than they inhibit each other, while in spatially structured populations, coexistence can occur even when interspecific competition between species intraspecific competition within patches when species vary along life history tradeoffs. Species outcompeted in a patch because they are more sensitive to interspecific competition can persist by colonizing newly disturbed patches more quickly. Here we analyze an alternative formulation of the Lotka-Volterra competition model, one in which the competitive impact on species’ population growth rates does not necessarily scale with intrinsic growth rates. This allows us to see the role that tradeoffs involving variation in intrinsic growth rates may play in coexistence even in well-mixed populations.

Results/Conclusions

We find that in this model two competitors can stably coexist through a variation along a life history tradeoff. One species that is more sensitive to competition from the other species (relative to its intraspecific competition) can coexist with the other if it has a higher intrinsic growth rate. This highlights that coexistence through such tradeoffs does not require spatial structure and may be of even more widespread importance than previously thought. It also highlights that coexistence can occur when measures of intraspecific competition are less than of interspecific competition, even in well-mixed populations. We also present arguments that this alternative formulation of the Lotka-Volterra model may in many circumstances be more appropriate. This work suggests an alternative perspective on the potential nature of niche differentiation and the role of spatial structure in coexistence.