Interaction Milieu Explains Performance of Species in Simple Food Webs along an Environmental Gradient

Abstract

Species interact with each other in a complex network of relationships that can be modeled as an interaction milieu, i.e. a biotic background with which the species interacts. The interaction milieu is given by the frequency distribution of traits that are important to a given interaction; hence this approach provides a direct link between organism performance, abiotic environmental conditions and interspecific interactions. In this study, we investigate how performance of component species is affected by the interaction milieu along an environmental gradient. We specifically addressed two questions: 1) can the interaction milieu shift species performance away from the niche optimum?, and 2) do species have a higher invasive potential if they have divergent trait values compared to the interaction milieu? We developed a model where a target species showing a given performance response curve to an environmental gradient, i.e., generalist or specialist, interacts with predators and competitors. The predictions of the model were compared with empirical findings on the abundance patterns of species along a salinity gradient in a green beach ecosystem. Green beaches are characterized by their strong gradients and spatial variability in abiotic factors, and their relatively simple food web consisting of Collembola species and their spider predators. First, our results showed that interaction milieu can displace species from their fundamental niche optimum. This led to abundance patterns that cannot be predicted by species performance response curves alone, emphasizing the importance to include ecological interactions. Second, species failed to invade their preferred part of the gradient if predators or competitors shared the target species' preference. Future studies should explore if the concept of interaction milieu can be generalized across trophic levels, and search for traits that are important on deciding the outcome of ecological interactions. Furthermore, the identification of the relevant response traits and their frequency distribution, in combination with trait plasticity of species in interaction milieus might be a step forward to link evolutionary principles to ecological networks, and vice versa.

Heated communities: large inter- and intraspecific variation in heat tolerance across trophic levels of a soil arthropod community

“…Our experiment was conducted on the southwest side of the barrier island of Schiermonnikoog (53.46896°N, 6.13914°E), The Netherlands. The ecosystem consisted of a vegetated beach which was characterized by a rather low diversity of plant species and a relatively low species richness of the arthropod community compared to other terrestrial ecosystems (van Wingerden and den Hollander 1981 ; Ellers et al 2011 ). This allowed us to collect individuals from all the dominant taxa living on the soil surface and include them in our study.…”

Handbook of protocols for standardized measurement of terrestrial invertebrate functional traits

“…In addition, functional traits, such as species temperature tolerance and drought resistance, are often missing or inferred from the abiotic conditions at the (micro)habitats where they have been observed and not measured directly on individuals. However, (micro)habitat selection of species and realized niche in general might result from interactions between species rather than physiological and phenological characteristics of single individuals and populations (Colwell & Fuentes ; Ellers, Dias & Berg ; Araujo et al . ; Colas et al .…”

“…In addition, functional traits, such as species temperature tolerance and drought resistance, are often missing or inferred from the abiotic conditions at the (micro)habitats where they have been observed and not measured directly on individuals. However, (micro) habitat selection of species and realized niche in general might result from interactions between species rather than physiological and phenological characteristics of single individuals and populations (Colwell & Fuentes 1975;Ellers, Dias & Berg 2010;Araujo et al 2013;Colas et al 2014;He & Bertness 2014), but see also Warren, Giladi & Bradford (2010). The use of such inferred traits as predictors of community and ecosystem processes has been strongly discouraged (Violle et al 2007), advocating for traits to be measured on individual organisms.…”

Environmental niche and functional role similarity between invasive and native palms in the Atlantic Forest

“…Archontophoenix cunninghamiana has the potential to expand its environmental niche into areas with less seasonal precipitation. This expansion suggests that invasive species can expand their niche quickly and occupy different environmental conditions in invaded areas (Broennimann et al 2007;Ellers et al 2011;Frost et al 2019). Nonetheless, areas that are predicted as areas of potential invasion but have high uncertainty in the prediction, such as the northwest areas of the Atlantic forest (São Francisco biogeographical region), should be interpreted with caution (Pearson et al 2006).…”