Individual‐based networks reveal the highly skewed interactions of a frugivore mutualist with individual plants in a diverse community

Abstract

While plant-animal interactions occur fundamentally at the individual level, the bulk of research examining the mechanisms that drive interaction patterns has focused on species or population levels. In seed-dispersal mutualisms between frugivores and plants, little is known about the role of space and individual-level variation among plants in structuring patterns of frugivory and seed dispersal in a plant community. Here we use a zoocentric approach to examine how space and variation between individual plants affect movement and visitation by frugivores foraging on individual fruiting plants. To do this, we used a spatially explicit network approach informed by observations of the movement and foraging of a frugivorous lemur species Eulemur rubriventer among individual plants in a diverse plant community in Madagascar. The resulting hierarchical networks show a few individual plants receiving the bulk of the interactions, demonstrating that a generalist frugivore species could act as an individual-plant specialist within a plant community. The few individual plants that dominated interactions with lemurs shaped the modular spatial structure of frugivory interactions in the community and facilitated visitation to near neighbors. This interaction structure was primarily driven by extrinsic factors, as lemur movements among plants were significantly influenced by the individual plant's spatial position and the fruiting plant richness in its immediate neighborhood. Individual plants in central spatial locations with large fruit crops received the most visits. The observed inequality in the interactions of a generalist frugivore within a highly diverse plant community highlights the importance of considering individual-level variation for essential ecosystem processes such as seed dispersal.

Reciprocity and interaction effectiveness in generalised mutualisms among free-living species

“…Other factors not analysed here, such as secondary compounds, fruit accessibility or fruiting neighbourhood could also be affecting consumption patterns (Moermond & Denslow 1985; Cipollini & Levey 1997; Carlo et al . 2007; Tonos et al . 2021).…”

“…These traits are well known to affect frugivory (Sallabanks 1993;Ortiz-Pulido et al 2007;Schupp et al 2019) and are as well related to the ontogeny, growth and size hierarchies in plant populations (Weiner & Solbrig 1984). Other factors not analysed here, such as secondary compounds, fruit accessibility or fruiting neighbourhood could also be affecting consumption patterns (Moermond & Denslow 1985;Cipollini & Levey 1997;Carlo et al 2007;Tonos et al 2021).…”

Drivers and consequences of structure in plant–lemur ecological networks

“…Additionally, rather than intrinsic functional traits, plant-lemur interactions may be driven by extrinsic factors (e.g. plant richness, Tonos et al, 2021). Effects of plant traits on connectivity were smaller than lemur traits, possibly because we did not include feeding preference traits (e.g.…”

“…Although widely used in social network analyses, ERGMs have only recently been applied to ecological networks (e.g. Arroyo‐Correa et al, 2021; Fuzessy et al, 2022; Tonos et al, 2021). In this study, we extend previous ecological applications of ERGMs that focused on one trophic level, jointly analysing attributes of both trophic levels and incorporating phylogenetic effects to improve our understanding of plant–animal interactions in complex networks.…”

Pollinator individual‐based networks reveal the specialized plant–pollinator mutualism in two biodiverse communities

“…Tur et al (2014) suggested that individual flower visitor‐plant species pollen transport networks were more specialized than species–species networks, and generalist pollinator species often comprised specialist pollinator individuals. The two limited cases strongly suggest that pollination networks based on pollinator individual level could be more specialized than those based on pollinator species level (Araújo et al, 2011; Des Roches et al, 2018; Tonos et al, 2021), indicating that pollination networks based on pollinator individual level could fill the gap between high pollinator fidelity and the highly generalized pollination networks (Arceo‐Gómez et al, 2016; Lázaro et al, 2008).…”