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25 August 2020 Diet and Trophic Niche of Two Sympatric Physalaemus Species in Central Brazil
Priscilla Guedes Gambale, Marlene Rodrigues da Silva, Fabrício Hiroiuki Oda, Rogério Pereira Bastos
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Abstract

Given the increasing use of sympatric species to investigate niche differentiation and resource partition in biological communities, our study analyzes diet composition differences and trophic niche overlap between the sympatric species Physalaemus cuvieri and P. atim in the municipalities of Silvânia and Leopoldo Bulhões, Brazil. We used stomach flushing to obtain stomach contents from each individual and identified 11 prey categories for P. cuvieri and 17 for P. atim. Isoptera had the highest proportional volume in both species. No difference was found in the mean prey volume per stomach. Detrended correspondence analysis distribution scores indicated a greater diet breadth for P. atim than P. cuvieri, which is consistent with a higher trophic niche breadth in P. atim than P. cuvieri. According to a multi-response permutation procedure analysis, P. cuvieri and P. atim have different diet compositions. Our findings suggest that these congeneric species occupy sufficiently different dietary niches to enable them to persist in sympatry.

INTRODUCTION

Ecologists have applied sympatric species models seeking to understand species coexistence and community structure by investigating niche differentiation and resource partitioning in biological communities. Coexistence of sympatric species derives from coevolution through their process of adapting to a habitat by avoiding competition with reduced overlap of resource use regarding at least one niche dimension (Leibold and McPeek, 2006). Thus, spatial and temporal dimensions as well as food availability are regarded as the most important factors in niche differentiation (Pianka, 1974; Schoener, 1974).

Many studies have found differences in the trophic niches of sympatric species of tropical anurans, including findings on food resource overlap (e.g., de Paula-Lima et al., 2010; Sabagh et al., 2012; Oliveira et al., 2015) and identification of food resource partitioning in prey size, feeding time period, and predator size classes (e.g., Lima and Magnusson, 1998; Menin et al., 2005). These studies are useful to determine ecological differences of closely related species.

Physalaemus Fitzinger, 1826 is one of the most speciose genera of Leptodactylidae Werner, 1896 (1838), with 48 recognized species widely distributed throughout South America, including from the Guianas, the lowlands of southern Venezuela, the llanos of southeastern Colombia, western Ecuador, Bolivia, Paraguay, Uruguay, northern and central Argentina, and Brazil (Nascimento et al., 2005; Lourenço et al., 2015; Frost, 2020). Brazil harbors 44 species of Physalaemus (Frost, 2020). Physalaemus cu– vieri Fitzinger, 1826 is widely distributed throughout South America, while P. atim Brasileiro and Haddad, 2015 has been recorded only in the municipalities of Campo Limpo de Goiás (type locality) and Terezópolis de Goiás (Brasileiro and Haddad, 2015; Frost, 2020). Distributions of both species overlap in central Brazil, with sympatry in open Cerrado areas of Goiás state. Detailed studies on the diet of P. cuvieri have been carried out in some localities (Moreira and Barreto, 1996; Becker et al., 2007; Araújo et al., 2009; Menin et al., 2015; Leivas et al., 2018), but no studies on the diet of P. atim have been conducted.

Our study provides information on the diet and trophic niche overlap of Physalaemus cuvieri and P. atim in aquatic habitats of open Cerrado areas in central Brazil and report on (1) the diet composition of the species at the study site and (2) the food niche overlap between them. Physalae– mus species are morphologically, behaviorally, and phylogenetically similar, which suggests that sympatric species of the genus might show similar dietary compositions, as has been reported for other sympatric anuran species (Sabagh et al., 2012; Oliveira et al., 2015). However, we expect to find differences in dietary composition, as this would enable their sympatry by way of low trophic niche overlap.

MATERIALS AND METHODS

Study site

Our study encompassed nine cattle ranches (Table 1) located in the municipalities of Silvânia and Leopoldo Bulhões, central Goiás state, central Brazil (Fig. 1). The ranches are characterized by Cerrado sensu lato physiognomies (campo limpo, areas without shrubs or trees; campo sujo, areas with scattered small trees and shrubs; Oliveira-Filho and Ratter, 2002) surrounded by extensive pasture areas. We surveyed one water body per ranch, totalling nine water bodies (Fig. 2), which were selected due to the sympatric occurrence of Physalaemus cuvieri and P. atim in those locations.

Figure 1.

Map of the study sites. Distribution of the surveyed water bodies (survey points) in nine cattle ranches in the municipalities of Silvânia and Leopoldo Bulhões, Goiás state, central Brazil. See general views of the surveyed water bodies in Figure 2.

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Table 1.

Surveyed water bodies in nine cattle ranches in the municipalities of Silvânia and Leopoldo Bulhões, Goiás state, central Brazil.

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DATA COLLECTION

We conducted 29 expeditions between December 2013 and February 2014 during the breeding season of most anuran species of the region, using randomized order to avoid temporal pseudoreplication. Nocturnal surveys (18:00–00:00)