Effect of oil palm (Elaeis guineensis Jacq.) plantations on individual-level diet variation of Hylaeamys megacephalus (G. Fisher 1814) (Rodentia, Cricetidae) in eastern Amazon Forest

Simone Almeida Pena,Ana Cristina Mendes-Oliveira

doi:10.1590/1676-0611-bn-2018-0597

Abstract

Abstract: In this study we described the diet of Hylaeamys megacephalus (G. Fisher, 1814) and investigated the degree of individual variation in the diet of this species among the Amazon Forest and the oil palm plantation. We analyzed the stomach contents of 36 individuals, of whom 11 were collected in the forest and 25 captured in the palm oil palm plantation. The H. megacephalus diet consisted of 18 food items, of which 12 were animal composition and eight were vegetable composition. The niche amplitude of the species was narrower in the forest area (Baforest = 0.013) compared to the palm tree plantation area (Bapalm = 0.478). This shows that individuals have greater niche overlap in forest areas, while in the plantation areas the animals expand their food niche. In addition, the values of the mean of the individual diet in relation to the diet of the entire population were lower in the palm oil palm plantation environment (ISpalm = 0.164) than in the Forest environment (ISforest = 0.357), indicating a high specialization in the palm oil plantation. These results indicate a population mechanism to reduce intraspecific competition in response to scarce resources.

Highlights

IntroductionThe individual specialization has been considered as an endogenous mechanism of population in response to several factors, such as environmental variations (eg. habitat changes, seasonality or daily periods), ecological pressures (eg. predation, competition, reproductive period) and resource polymorphisms (Skulason & Smith 1995, Bolnick et al 2003)
The individual specialization has been considered as an endogenous mechanism of population in response to several factors, such as environmental variations, ecological pressures and resource polymorphisms (Skulason & Smith 1995, Bolnick et al 2003)
The H. megacephalus diet is composed of 18 food item of which 10 are of animal origin (Orthoptera, Coleoptera, Dermaptera, Heteroptera, Lepdoptera, Blattaria, Formicidae, Curculionidae, Cerambycidae and Araneae) and eight are of vegetal origin, as plants fragments and oil palm fragments (Table 1)

Summary

Introduction

The individual specialization has been considered as an endogenous mechanism of population in response to several factors, such as environmental variations (eg. habitat changes, seasonality or daily periods), ecological pressures (eg. predation, competition, reproductive period) and resource polymorphisms (Skulason & Smith 1995, Bolnick et al 2003). The individual specialization would be a mechanism to reduce intraspecific competition (Roughgarden 1972, Svanbäck & Persson 2004) in populations with high rates of individual specialization, where each individual typically uses a resource set significantly smaller than the set of resources used by the population as a whole and with less overlap of individual niches (Bolnick et al 2003). Most of these theories have been commonly studied in communities of fish, insects and amphibians (Araújo & Gonzaga 2007, Araújo et al 2009, Hannah et al 2013, Bolnick et al 2014, Costa et al 2015), but in mammalian species the knowledge about individual specialization and polymorphism of resources is scarce (Olsson et al 2007, Martins et al 2008, Camargo et al 2013, Pires et al 2013, Svanbäck et al 2015)

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