Stable isotope analysis of trophic niche in two co-occurring native and invasive terrapins, Emys orbicularis and Trachemys scripta elegans
- 284 Downloads
A trophic niche overlap in native and alien turtle species can lead to competitive interactions whereby allochthonous turtles may outcompete autochthonous individuals and eventually affect viability of natural populations. The European pond turtle (Emys orbicularis) is an autochthonous species threatened by habitat encroachment and competition with the red-eared slider (Trachemys scripta elegans). The latter is an invasive species introduced in Europe from midwestern United States as a pet and now widespread in the natural habitats of E. orbicularis. The extent of trophic competition between E. orbicularis and T. s. elegans in northern Italy was assessed by nitrogen and carbon stable isotope analysis (δ15N and δ13C). We used blood and claw samples in order to obtain information on diet components over a short- (3–4 months) and long-term (12 months) time frame, respectively. Analysis of claw samples showed a clear separation between the diets of adults of the two species, but suggested a trophic overlap among adult invaders and young autochthonous turtles. Blood samples, on the other hand, revealed a partial overlap between niches, indicating a short-term correspondence in diet composition between species. We found that, for specific life stages and times of the year, there is potential for trophic competition, which may have important consequences for the management and conservation of E. orbicularis in Italy.
KeywordsInvasive species Food competition Freshwater turtles Emys orbicularis Trachemys scripta elegans Carbon and nitrogen stable isotopes
We would like to thank F. Frizzi for his support during the preparation of the manuscript. We are also grateful to one anonymous reviewer for his/her helpful comments.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
- Aresco MJ, James FC (2005) Ecological relationships of turtles in northern Florida lakes: a study of omnivory and the structure of a lake food web. Florida Fish and Wildlife Conservation Commission, TallahasseeGoogle Scholar
- Ferrari V, Lavezzi F (1995) I fontanili e i bodri in provincia di Cremona. Centro di documentazione ambientale, Provincia di Cremona. Primastudio, CremonaGoogle Scholar
- Krawchuk MA, Brooks RJ (1998) Basking behavior as a measure of reproductive cost and energy allocation in the painted turtle, Chrysemys picta. Herpetologica 54:112–121Google Scholar
- Lara NRF, Marques TS, Montelo KM, de Ataìdes AG, Verdade LM, Malvasio A, de Camargo PB (2012) A trophic study of the sympatric Amazonian freshwater turtles Podocnemis unifilis and Podocnemis expansa (Testudines, Podocnemidae) using carbon and nitrogen stable isotope analyses. Can J Zool 90:1394–1401CrossRefGoogle Scholar
- Lefevre K, Brooks RJ (1995) Effects of sex and body size on basking behavior in a Northern population of the painted turtle, Chrysemys picta. Herpetologica 51:217–224Google Scholar
- Lowe S, Browne M, Boudjelas S, De Poorter M (2000) 100 of the world’s worst invasive alien species. A selection from the global invasive species database. Invasive Species Specialist Group, AucklandGoogle Scholar
- Pianka ER (1981) Competition and niche theory. In: May RM (ed) Theoretical ecology: principles and applications. Blackwell, Oxford, pp 167–196Google Scholar
- R Core Team (2014) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/
- Rollinat R (1934) La Vie des Reptiles de la France Centrale. Librairie Delagrave, ParisGoogle Scholar
- Sokal RR, Rohlf FJ (2012) Biometry: the principles and practice of statistics in biological research. WH Freeman and Co, New YorkGoogle Scholar
- Zuffi MAL, Gariboldi A (1995) Sexual dimorphism in Italian populations of the European pond terrapin, Emys orbicularis. In: Llorente GA, Montori A, Santos X, Carretero MA (eds) Scientia Herpetologica. Asociación Herpetológica Española, Barcelona, pp 124–129Google Scholar