Spiders follow an ideal free distribution based on traits of the plant community

Abstract

1. Understanding the distribution of organisms is a central issue in ecology. Some animal densities are directly determined by resource availability(i.e. the ideal free distribution model, IFD). Hence, animals freely occupy the available patches so that the payoff is ideally maximised according to resource exploitation and competition. Based on its assumptions, tests of the IFD should be made with animals presenting high motility and sensitivity to specific habitat characteristics.2. This study demonstrates how traits from the plant community influence the distribution of two cobweb spiders, Helvibis longicauda and Chrysso intervales, on a forest understory.3. Spider abundance was positively correlated to the availability of broadleaves (i.e. suitable sites) along patches. They show high topophilia (i.e. preferences based on microhabitat structural characteristics) for roof‐like leaves, which provide shelter to build webs underneath. Alternatively, higher numbers of pinnate fern fronds, a trait that is unsuitable to support the three‐dimensional webs of those species, translated to decreased abundance. Numbers of suitable and unsuitable sites were negatively correlated, indicating that their proportion on patches drives spider abundance. Finally, spider abundance along 22 suitable plant species was influenced by the number of microhabitats provided per species rather than by their phylogenetic identities.4. We corroborate the IFD, demonstrating that simple consumer–resource relationships may occur on complex/multi‐species environments, such as forests. Dispersion and topophilic microhabitat selection may be driven by substrate availability and competition. Importantly, we provide insights based on the whole plant community, while previous evidence was limited to a single or a few species.