Incorporating alternative interaction modes, forbidden links and trait‐based mechanisms increases the minimum trait dimensionality of ecological networks

Abstract

1. Individual-level traits mediate interaction outcomes and community structure. It is important, therefore, to identify the minimum number of traits that characterise ecological networks, that is, their 'minimum dimensionality'. Existing methods for estimating minimum dimensionality often lack three features associated with increased trait numbers: alternative interaction modes (e.g. feeding strategies such as active vs. sit-and-wait feeding), trait-mediated 'forbidden links' and a mechanistic description of interactions. Omitting these features can underestimate the trait numbers involved, and therefore, minimum dimensionality. We develop a 'minimum mechanistic dimensionality' measure, accounting for these three features. 2. The only input our method requires is the network of interaction outcomes. We assume how traits are mechanistically involved in alternative interaction modes. These unidentified traits are contrasted using pairwise performance inequalities between interacting species. For example, if a predator feeds upon a prey species via a typical predation mode, in each step of the predation sequence, the predator's performance must be greater than the prey's. We construct a system of inequalities from all observed outcomes, which we attempt to solve with mixed integer linear programming. The number of traits required for a feasible system of inequalities provides our minimum dimensionality estimate.

Ant protection effectiveness in myrmecophytes and extrafloral nectary plants

“…We are aware that some interactions in the plant–ant network may be forbidden links, that is, interactions that are likely to not occur (Kiziridis et al., 2020). Given the spatial scale of our data (information retrieved from 56 papers that bait‐tested ants in eight countries), the forbidden links were expected to occur.…”

The best plant-guarding ants in extrafloral nectaried plants and myrmecophytes according to baiting tests

“…We are aware that some interactions in the plant-ant network may be forbidden links, i.e., interactions that are likely to not occur (Kiziridis et al, 2020). Given the spatial scale of our data (information retrieved from 56 papers that bait-tested ants in eight countries), the forbidden links were expected to occur.…”