Differential trophic traits between invasive and native anuran tadpoles

Olatz San Sebastián,Eudald Pujol-Buxó,Núria Garriga,Gustavo Llorente,Álex Richter-Boix

doi:10.3391/ai.2015.10.4.10

Abstract

How trophic resources are managed is a key factor in our understanding of the success of invasive species. In amphibians that usually occupy ephemeral ponds, the capacity to acquire resources and food selection are especially important because as a pond dries, the larval density increases and food resources are limited. Abundant and high-quality food can increase the final size and reduce the duration of development of amphibians. The aim of this work was to assess the trophic traits of tadpoles of the invasive (originally North African) anuran Discoglossus pictus compared to those of native European Epidalea calamita tadpoles under laboratory conditions. Food of two different levels of quality was supplied, and the feeding activity and food preference of the two species were analysed alone and in co-occurrence. D. pictus was capable of modifying its behaviour and food preferences; while E. calamita displayed much milder differences between treatments. Both alone and in co-occurrence with the native species, the invasive tadpoles obtained higher feeding activity values and showed a stronger preference for high-quality food. Additionally, when high densities of the two species shared food resources, the feeding activity results indicated potential displacement of the native tadpoles to lowquality resources. D. pictus thus presents trophic traits that are favourable for invasion and could limit the fitness of E. calamita when resources are limited or there is a risk of pond desiccation.

Highlights

Invasion by alien species is one of the most important threats to the balance of ecosystems and community structure, and the second most significant cause of biodiversity loss on the global scale (Levine et al 2003)
D. pictus presents trophic traits that are favourable for invasion and could limit the fitness of E. calamita when resources are limited or there is a risk of pond desiccation
The feeding activity of D. pictus ranged from 25% to 72%, while that of E. calamita did not exceed 20% in any treatment

Summary

Introduction

Invasion by alien species is one of the most important threats to the balance of ecosystems and community structure, and the second most significant cause of biodiversity loss on the global scale (Levine et al 2003). When an alien amphibian species is introduced, its efficiency at exploiting the available resources during larval stages can be a key factor for the successful establishment of the species and may define its invasiveness, because of the vulnerability during this phase and the crucial effect of food on the development of tadpoles and the subsequent development of toadlets (Werner 1986; Scott 1994; Tejedo et al 2000). The effects of diet on the breeding success and metamorphic fitness of amphibians have been repeatedly documented (Kupferberg 1997; Babbitt et al 2000; Álvarez and Nicieza 2002; Jefferson 2014) Both food quantity and food quality are crucial for their development: tadpoles cannot fully develop under desiccated conditions when food is scarce (Enriquez-Urzelai et al 2013), or low in protein content (Nathan and James 1972; Steinwascher and Travis 1983; McCallum and Trauth 2002; Richter-Boix et al 2007). Optimal exploitation of available resources by tadpoles ensures fast growth and high performance, favouring the establishment and spread of introduced amphibian species

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Conclusion