Competition and predation in simple food webs: Intermediately strong trade-offs maximize coexistence

Competition and predation are fundamental interactions structuring food webs. However, rather than always following these neat theoretical categories, mixed interactions are ubiquitous in nature. Of particular importance are omnivorous species, such as intraguild predators that can both compete with and predate on their prey. Here, we examine tradeoffs between competitive and predatory capacities by analysing the entire continuum of food web configurations existing between purely predator-prey and purely competitive interactions of two consumers subsisting on a single resource. Our results show that the range of conditions allowing for coexistence of the consumers is maximized at intermediately strong tradeoffs. Even though coexistence under weak tradeoffs and under very strong tradeoffs is also possible, it occurs under much more restrictive conditions. We explain these findings by an intricate interplay between energy acquisition and interaction strength.
KEYWORDS: Food web; Community structure; Coexistence; Trade-off; Competition; Predation

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