Diet of the gracile mouse opossum Gracilinanus agilis (Didelphimorphia: Didelphidae) in a neotropical savanna: intraspecific variation and resource selection

Oliveira

Ribeiro

et al. 2019

Ecology and Evolution

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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.

Section: Methodsmentioning

confidence: 99%

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

Oliveira

Ribeiro

et al. 2019

Ecology and Evolution

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“…Its diet is composed mainly of insects, although fruits may act as an important food source during the dry season, especially for reproductive females (Lamberto 2011;Camargo et al 2014). Reproduction is usually synchronized among individuals and a biased sex-ratio toward males has already been reported in previous populations (Aragona and Marinho-Filho 2009;Andreazzi et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Semelparity in a population of Gracilinanus agilis (Didelphimorphia: Didelphidae) inhabiting the Brazilian cerrado

Lopes¹,

Leiner²

2015

Mammalian Biology

a b s t r a c tAlthough reproducing once in a lifetime (i.e. semelparity) is considered rare among vertebrates, it has evolved at least five times in two distantly related marsupial families; the Australian Dasyuridae and South American Didelphidae. The major aim of this research was to describe the population dynamics, reproductive strategy and associated life-history traits of the agile gracile mouse opossum, Gracilinanus agilis, in order to position the species along the fast-slow life-history continuum. Sampling was carried out through mark-recapture, from August 2010 to April 2013, in a Brazilian area of cerrado. Reproductive activity was seasonal and synchronized among females, and occurred from July to January/February. After mating, population size decreased due to male disappearance, which seems to be explained by postmating male die-off. Phylogenetic predisposition toward semelparity in Gracilinanus lineage and intense competition for females may contribute to male die-off, as indicated by several evidences such as malebiased sex ratio, signs of aggression in reproductive males, and a pronounced gain in male body mass and size prior to mating. Although two litters were produced, most females disappeared after weaning their young, indicating post-reproductive senescence and resulting in discrete, non-overlapping generations, characterizing semelparity in this population of G. agilis.

“…In the present study, we investigated the role of both inter‐ and intra‐individual variation of niche width on the patterns of population niche variation of the gracile mouse opossum Gracilinanus agilis on an intra‐annual timescale. This insectivore–omnivore marsupial (Camargo et al ., ) occurs in a highly seasonal, savanna‐like vegetation type (i.e. the Brazilian Cerrado).…”

Section: Introductionmentioning

confidence: 99%

Intra- and inter-individual variation show distinct trends as drivers of seasonal changes in the resource use of a neotropical marsupial

Ribeiro

et al. 2014

Biol J Linn Soc Lond

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Individual specialization can influence important ecological and evolutionary traits and both inter‐ and intra‐individual variation in resource use can drive niche shifts in natural populations. We evaluated the predominance of these two factors for determining seasonal differences in the trophic niche of the didelphid marsupial Gracilinanus agilis (Burmeister, 1854) in the highly seasonal Brazilian savanna. In the three sampled sites, the population of G. agilis increased its dietary niche width in the warm–wet season, when food resources are more abundant, and there were no differences between sexes and no interaction between season and sex. However, the evaluation of intra‐individual variation indicated that females reduce the number of items consumed during the warm–wet season, whereas males show no seasonal differences. Inter‐individual variation nonetheless followed the overall population pattern because both sexes increased their spread with respect to food‐item consumption in the warm–wet season. Additionally, we found positive relationships between body length and diet only in the warm–wet season, when larger animals fed more on invertebrates and less on fruits than the small ones. Our results show a previously unknown pattern for mammals, in which the trophic niche is wider during the high‐resource season as a result of inter‐individual variation along the body‐size axis. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 737–747.