Availability of food resources and habitat structure shape the individual‐resource network of a Neotropical marsupial

Abstract

Spatial and temporal variation in networks has been reported in different studies. However, the many effects of habitat structure and food resource availability variation on network structures have remained poorly investigated, especially in individual‐based networks. This approach can shed light on individual specialization of resource use and how habitat variations shape trophic interactions. To test hypotheses related to habitat variability on trophic interactions, we investigated seasonal and spatial variation in network structure of four populations of the marsupial Gracilinanus agilis in the highly seasonal tropical savannas of the Brazilian Cerrado. We evaluated such variation with network nestedness and modularity considering both cool‐dry and warm‐wet seasons, and related such variations with food resource availability and habitat structure (considered in the present study as environmental variation) in four sites of savanna woodland forest. Network analyses showed that modularity (but not nestedness) was consistently lower during the cool‐dry season in all G. agilis populations. Our results indicated that nestedness is related to habitat structure, showing that this metric increases in sites with thick and spaced trees. On the other hand, modularity was positively related to diversity of arthropods and abundance of fruits. We propose that the relationship between nestedness and habitat structure is an outcome of individual variation in the vertical space and food resource use by G. agilis in sites with thick and spaced trees. Moreover, individual specialization in resource‐rich and population‐dense periods possibly increased the network modularity of G. agilis . Therefore, our study reveals that environment variability considering spatial and temporal components is important for shaping network structure of populations.

Seasonal isotopic niche of a rodent: High between‐individual variation but no changes in individual niche width during the rich‐resource period

“…The frugivorous R. macrurus exhibited a dynamic trophic niche across seasons. In the Cerrado, the warm-wet season usually supports a higher abundance and diversity of fruit and arthropod resources (Gouveia & Felfili, 1998;Pinheiro et al, 2002;Silva et al, 2011), a pattern previously documented in our study area (see Camargo, Oliveira, et al, 2019, Our results indicated that the arboreal forest-specialist R. macrurus feeds mostly on fruit, with little contribution of insects to its diet. It was understood that this species is a frugivore and granivore (Paglia et al, 2012), but this is now verified based on fecal content measured in the present study.…”

“…Understanding individual specialization can be particularly useful to elucidate population niche patterns for animal species that experience intense inter-and intraspecific competition and marked seasonality regarding food-resource availability (Bolnick et al, 2010;Camargo, Oliveira, et al, 2019;Svanbäck & Bolnick, 2007).…”

“…For our study species, we expected competition to be higher during the warm-wet season. During this season, resource availability (of both arthropod and fruits) is greater (Camargo, Oliveira, et al, 2019;Gouveia & Felfili, 1998;Pinheiro et al, 2002;Silva et al, 2011), and most small mammal species (including R. macrurus) exhibit population peaks (Mares & Ernest, 1995). These coinciding peaks potentially increase intra-and interspecific competition due to the increase in forager densities.…”

Wing morphology predicts individual niche specialization in Pteronotus mesoamericanus (Mammalia: Chiroptera)

“…However, it is hard to predict how behaviorally flexible individuals with different wing shapes can be during transitions between seasons. Changes in habitat structure and food availability in a Neotropical seasonal dry forest has been linked with differential spatial and resource use between individuals in a mammal species [81]. Thus, it is possible that both variables play a role on how bats with different wing morphologies explore and specialize in their environment.…”

“…Network approaches can provide useful insights into inter-individual variation in resource use [23][24]. The existing studies that have examined networks composed of individuals within a population have reported different levels of specialization [25][26], in which the diets of specialist individuals are nested within the diets of the generalists [7,27].…”