Highly nested diets in intrapopulation monkey–resource food webs

Abstract

Recently several studies have focused on the structure of ecological networks to provide insights into ecological and coevolutionary dynamics of interacting species. However, rarely have the tools of ecological networks been used to understand how feeding relationships vary among individuals of the same population. Here we use 7 years of data and network analyzed to examine the intrapopulation diet variation in a group of howler monkeys (Alouatta palliata). We show that individual monkey-resource food webs are nested, but not modular and the stability of these patterns is independent of time of day or season. Our findings indicated that individuals do not forage randomly when compared to null models and that the diets of more selective monkeys represent subsets of the diets of other individuals. Moreover, there are no subgroups that eat a particular set of available plant species more frequently than other sets, suggesting that the spatial strategy of group foraging plays an important role in the feeding ecology of each group given that individuals of the same group tend to share similar resources while the group remains at a feeding site. Since the diets of more selective individuals are a subset of other monkeys, we suggest that more selective monkeys are able to outcompete others for preferred foods. Additionally, we did not observe differences in nutritional content or spatial abundance of more frequently eaten plant species when compared with less frequently eaten species, but in most cases, the more frequently eaten plant species were Ficus (Moraceae). This reinforces the important role that Ficus trees play in howler monkey feeding ecology, likely due to its year-round availability.

Tropical Forest Fragmentation Affects Floral Visitors but Not the Structure of Individual-Based Palm-Pollinator Networks

“…Variation in pollinator visitation frequency to flowers can generate complex networks among individuals of the same plant species. Similar studies have been conducted involving individual-based networks in other interaction systems using an intrapopulation approach, such as sea otters-prey, didelphid marsupials-arthropods, snails and fruits, monkeys-fruiting plants, frogs, ant-plants, and lizards-diets [ 28 , 29 , 30 , 31 , 32 , 33 ]. However, to our knowledge only two studies have evaluated the networks of plant-pollinator interactions among individuals within populations [ 26 , 27 ].…”

Peer Review #1 of "The role of sex and age in the architecture of intrapopulation howler monkey-plant networks in continuous and fragmented rain forests (v0.1)"

“…Adults, though, consumed the greatest variety of plant species and items. Male and female infants tended to consume more plant species in continuous forest than in fragments, whereas adult females were the most extreme "generalists" in the resulting networks (Dáttilo et al 2014). This study is the first one to show that the specialized diets of male and female infants determined the nested structure of primate-plant networks in howler monkey populations.…”

“…In our intrapopulation networks, plant species and monkeys are depicted as nodes, and their feeding interactions are depicted by links describing the use of plant species by individuals. Our qualitative approach in calculating nestedness decreases the probability of overestimating the amount of resources (e.g., leaves vs. fruits) ingested by monkeys (Dáttilo et al, 2014).…”

The role of sex and age in the architecture of intrapopulation howler monkey-plant networks in continuous and fragmented rain forests

“…In our intrapopulation networks, plant species and monkeys are depicted as nodes, and their feeding interactions are depicted by links describing the use of plant species by individuals. Our qualitative approach in calculating nestedness decreases the probability of overestimating the amount of resources (e.g., leaves vs. fruits) ingested by monkeys ( Dáttilo et al, 2014 ). Biologically, nestedness describes the organization of niche breadth in which more nested networks tend to have the highest niche overlap ( Blüthgen, 2010 ).…”

“…Several studies have used tools derived from network analysis to describe the dietary variation found in populations of animals with a focus on individual-based plant-animal networks ( Pires et al, 2011 ; Tinker et al, 2012 ; Cantor et al, 2013 ). Recently, it has been shown that intrapopulation primate-resource networks are highly nested: diets of specialist individuals are a subset nested within the diets of generalist individuals ( Dáttilo et al, 2014 ). There is no information, however, about potential factors determining such network structure.…”