Intricate trophic links between threatened vertebrates confined to a small island in the Atlantic Ocean.

Ricardo J Lopes,Raquel Vasconcelos,Catarina J Pinho,Bárbara Santos,Bastian Egeter,Vanessa A Mata,Mariana Seguro

doi:10.1002/ece3.5105

Abstract

Trophic networks in small isolated islands are in a fragile balance, and their disturbance can easily contribute toward the extinction vortex of species. Here, we show, in a small Atlantic island (Raso) in the Cabo Verde Archipelago, using DNA metabarcoding, the extent of trophic dependence of the Endangered giant wall gecko Tarentola gigas on endemic populations of vertebrates, including one of the rarest bird species of the world, the Critically Endangered Raso lark Alauda razae. We found that the Raso lark (27%), Iago sparrow Passer iagoensis (12%), Bulwer's petrel Bulweria bulwerii (15%), and the Cabo Verde shearwater Calonectris edwardsii (10%) are the most frequent vertebrate signatures found in the feces of the giant wall gecko. This work provides the first integrative assessment of their trophic links, an important issue to be considered for the long‐term conservation of these small and isolated island ecosystems.

Highlights

Small islands, due to their size, long‐lasting barriers to dispersal and occurrence of small populations adapted to these atypical environ‐ ments, are exposed to climatic, environmental and an‐ thropogenic pressures that increase the probability of extinction of native populations (Whittaker & Fernández‐Palacios, 2007)
Raso lark was present in 27% of the sam‐ ples, while the Iago sparrow was present in 12%
Bulwer's petrel was present in 15% and Cabo Verde shearwater present in 10%

Summary

| INTRODUCTION

Due to their size, long‐lasting barriers to dispersal and occurrence of small populations adapted to these atypical environ‐ ments, are exposed to climatic, environmental and an‐ thropogenic pressures that increase the probability of extinction of native populations (Whittaker & Fernández‐Palacios, 2007). A considerable egg predation was re‐ corded, without a clear identification of the predator(s), the researchers hypothesize the giant wall gecko T. gigas as being the most likely candidate (Donald et al, 2005; Donald, Ponte, Groz, & Taylor, 2003) This large nocturnal gecko, with an average snout‐ vent length >10 cm (Vasconcelos, Perera, Geniez, Harris, & Carranza, 2012) presently only occurs on Raso and nearby Branco islets. The evidence to date lead to the hypoth‐ esis that this gecko is the major (and perhaps only) natural predator of eggs of the Raso lark (Donald et al, 2005, 2003), and possibly of the Iago sparrow Passer iagoensis, the other abundant resident pas‐ serine species. The aim of the present study was to further characterize the ver‐ tebrate portion of the diet of giant wall geckos, using all samples col‐ lected in Raso across both the wet and dry seasons, with the primary goal of clarifying the trophic links, especially between these two spe‐ cies of conservation concern: the giant wall gecko and the Raso lark

| MATERIALS AND METHODS

| DISCUSSION

Findings

CONFLICT OF INTEREST