Niche differences between two sympatric whiptail lizards (Cnemidophorus abaetensis and C. ocellifer, Teiidae) in the restinga habitat of northeastern Brazil

Ejr Dias,Cfd Rocha

doi:10.1590/s1519-69842007000100006

Abstract

Differences among sympatric lizard species usually result from differences in the use of three resources: space, time and food or some combination of these three. However, differences in resource utilization among sympatric species may simply reflect their specific ecological needs rather than competitive pressures. In this study, we analyzed the temporal, spatial and food niche of two congeneric teiids (Cnemidophorus abaetensis and C. ocellifer) living sympatrically in the "restinga" habitat of Abaeté in the Salvador Municipality, Bahia State, Brazil to assess the degree of niche differentiation among them. The whiptail species overlapped considerably in an hourly activity (Ojk = 0.93), in microhabitat use (Ojk = 0.97) and in the prey items consumed (Ojk = 0.89). Differences in amount of vegetation in the microhabitats used by both lizard species may have contributed to differences in the activity period and in the distribution of the main prey eaten by these lizards which may, in turn, facilitate their coexistence in Abaeté. Although sympatric C. ocellifer and C. abaetensis in Abaeté differed only slightly in their use of microhabitats, period of activity and diet, the most important niche dimension segregating the two species seemed to be the food niche.

Highlights

Related sympatric species, by using similar resources and potentially competing, are usually expected to diverge on one of three niche axes to coexist (Pianka, 1973, 1986)
The first active C. ocellifer was sighted at 8 hours and, following that, the number of active lizards increased until reaching a maximum between 10 and 11 hours
The differences in activity period for these two whiptail lizards may be related to the differences in vegetation coverage in the microhabitats used (e.g. Grover, 1996)

Summary

Introduction

By using similar resources and potentially competing, are usually expected to diverge on one of three niche axes (space, time or food) to coexist (Pianka, 1973, 1986). If species were always packed as tightly together as they could be presumably they would differ by the minimum (limiting) amount (Begon et al, 1996). These differences in resource use may not necessarily indicate the occurrence of competition (Schoener, 1968; Pianka, 1973; Vitt, 1995; Vitt and Carvalho, 1995). Differences in resource utilization among sympatric species may reflect their specific ecological needs rather than competitive pressures

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Conclusion