Surprising effects of cascading higher order interactions

Abstract

Most species are embedded in multi-interaction networks. Consequently, theories focusing on simple pair-wise interactions cannot predict ecological and/or evolutionary outcomes. This study explores how cascading higher-order interactions (HOIs) would affect the population dynamics of a focal species. Employing a system that involves a myrmecophylic beetle, a parasitic wasp that attacks the beetle, an ant, and a parasitic fly that attacks the ant, the study explores how none, one, and two HOIs affect the parasitism and the sex ratio of the beetle. We conducted mesocosm experiments to examine these HOIs on beetle survival and sex ratio and found that the 1st degree HOI does not change the beetle’s survival rate or sex ratio. However, the 2nd degree HOI significantly reduces the beetle’s survival rate and changes its sex ratio from even to strongly female-biased. We applied Bayes’ theorem to analyze the per capita survival probability of female vs. male beetles and suggested that the unexpected results might arise from complex eco-evolutionary dynamics involved with the 1st and 2nd degree HOIs. Field data suggested the HOIs significantly regulate the sex ratio of the beetle. As the same structure of HOIs appears in other systems, we believe the complexity associated with the 2nd degree HOI would be more common than known and deserve more scientific attention.

Combining intransitive and higher‐order effects in a coupled oscillator framework: A case study of an ant community

“…That is, the actual density‐mediated predatory effect (odonate eats tadpole) may be trivial compared with the indirect action on competition by means of the very presence of the predator (tadpole smells predator and hides, leaving resources available for its competitor). The importance of these higher‐order effects has been long appreciated (Polis, 1991; Vandermeer, 1969) and recently gained prominence theoretically (Angulo et al, 2021; Bairey et al, 2016), complementing a substantial number of empirical examples (Barbosa et al, 2023; Hsieh et al, 2012, 2022; Hsieh & Perfecto, 2012; Offenberg, 2015; Schifani et al, 2020; Werner & Peacor, 2003).…”