Complementary Effects of Species Abundances and Ecological Neighborhood on the Occurrence of Fruit-Frugivore Interactions

Abstract

Species interactions are traditionally seen as the outcome of both ecological and evolutionary mechanisms. Among them, the two most frequently studied are the neutral role of species abundances in determining encounter probability and the deterministic role of species identity (traits and evolutionary history) in determining the compatibility of interacting species. Nevertheless, the occurrence of pairwise interactions also depends on the spatio-temporal context imposed by the ecological neighborhood (i.e., the indirect effect of other local species sharing traits and interaction potential with the focal ones). Although a few studies have begun to examine neighborhood effects on community interactions, these have not incorporated neighborhood structure as a complementary driver of pairwise interactions within an integrative approach. Here we describe the spatial structure of pairwise interactions between three fleshy-fruited tree species and six frugivorous thrush species within the same locality of the Cantabrian Range (Iberian Peninsula). Using a spatio-temporally fine-grained dataset sampled during 3 years, we aimed to detect spatial patterns of interactions and to evaluate their concordance across years. We also evaluated the simultaneous roles played by species abundance, species identity and the ecological neighborhood in determining the pairwise interaction frequencies based on fruit removal. Our results showed that the abundances of fruit and bird species involved in plant-frugivore interactions, and the spatial patterns of these interactions, varied among years, and this was mainly due to different fruiting landscapes responding to masting events of distinct plant species. Despite high interannual differences in species abundances and pairwise interaction frequencies, the main mechanisms underpinning the occurrence of pairwise interactions remained constant. Most of the variability in pairwise interactions was always explained by interacting fruit and bird species' abundances. Ecological neighborhood, characterized as the net quantity of forest cover, heterospecific fruit crops, and heterospecific bird abundances in the immediate surroundings, also affected pairwise interaction frequency through its indirect Donoso et al.Predicting Pairwise Interactions effects on the abundance of interacting bird species. Our results highlight the prevalence of neutral forces in highly generalized plant-frugivore assemblages as well as the influence of indirect interactions (competition and/or facilitation with other local species) as another important driver to consider when predicting pairwise interactions.

Frugivore biodiversity and complementarity in interaction networks enhance landscape‐scale seed dispersal function

“…On the other hand, frugivore biodiversity effects varied across components of seed dispersal, which may be partly associated with the occurrence of complex interactions between frugivore abundance and diversity (e.g., stronger effects of diversity at small abundances, Rumeu et al, ), though the present data do not facilitate testing this (but see Rodríguez‐Pérez, García, Martínez, & Morales, ). Even so, our results showed positive effects of diversity irrespective of abundance, probably related to sampling effects (the incorporation of functionally dominant frugivores, Schleuning et al, ), spatial complementarity (with a greater diversity meaning a higher variety of spatial behaviours after fruit consumption; Morales, García, Martínez, Rodríguez‐Pérez, & Herrera, ) or even interspecific interactions (with a greater diversity leading to facilitation in, e.g., fruit resource tracking; Donoso, García, Martínez, Tylianakis, & Stouffer, ).…”

The Strength and Drivers of Bird-Mediated Selection on Fruit Crop Size: A Meta-Analysis

“…Our results suggest that the number of fruit removed is the principal fitness component, at least at this reproductive stage. From the plant's perspective, fruit production should be maximized at the limit of the costs of fruit production to guarantee seed dispersal in a competitive scenario for seed dispersers (Howe and Estabrook, 1977;Albrecht et al, 2015;Donoso et al, 2017). It is worth mentioning that a greater dispersal success (absolute and relative) does not necessarily entails greater recruiting success, due to uncoupling between successive recruitment stages (Jordano and Herrera, 1995;Wang and Smith, 2002;Palacio et al, 2014; but see Blendinger et al, 2011).…”

Species temporal persistence promotes the stability of fruit–frugivore interactions across a 5‐year multilayer network

“…This suggests that there are interannual fluctuations in the frequency of interactions that may result from changes in relative fruit availability, for example due to variations in plant phenology constraining seed dispersers' preferences (Carlo & Morales, 2008;Donoso, García, Martínez, Tylianakis, & Stouffer, 2017;Rumeu et al, 2019).…”