Dispersal success of the European Treefrog in habitat connectivity projects

A genetic control project in the Reuss and Thur River valleys

European Treefrog (Hyla arborea) Photo: T. Reich (WSL)

DNA sampling on a European Treefrog Photo: P. Guldener

Species and habitats of conservation value are financially supported by Swiss Cantons and the Federal Government within the scope of habitat connectivity projects. Their aim is to enhance the dispersal of individuals (and gene flow) among remnant populations within fragmented landscapes. These processes are essential for the long-term survival of endangered species as they counteract the negative effects of genetic erosion. Habitat connectivity projects create new habitats (stepping stones) or connecting elements among habitats (corridors).

Controlling the success of connectivity measures is of great interest for nature conservation practice and is required by Swiss law. As connectivity projects also enhance habitat quality, the direct effects of habitat connectivity and habitat enhancement, are often indistinguishable. Control of success of actual habitat connectivity also raises a methodological problem for practical management, because surveys of dispersal are technically demanding and often cost, time and labor-intensive (e.g. capture-recapture of marked individuals). Furthermore, corresponding methods do not allow assessing whether migrating individuals also reproduced at new places and, consequently, whether gene flow occurred.

The goal of this project is to test the effect of ongoing habitat-connecting projects on an endangered species and, simultaneously, investigate the genetic structure of its remnant populations. The European Treefrog serves as a model species, and the exchange of individuals among habitat patches will be assessed with molecular genetic markers of high resolution. In addition to genetic analysis, a landscape analysis using data from a geographic information system (GIS) will be performed. In doing so, landscape elements structures will be evaluated with respect to their promotional or inhibitory impact on Treefrog dispersal. In order to determine fitness differences between the remaining Treefrog populations, tadpoles will be raised in a common garden experiment.

This project is supported by the Cantons of Argovia, Thurgau and Zurich as well as the MAVA foundation for nature conservation, the U.W. Linsi foundation, the Wolfermann-Nägeli foundation and the Seebachtal foundation.

Contact

• Rolf Holderegger