08 July 2010

An experiment among a pile of rocks — then and now

Back in the summer of 2006 when I and Tim Pearce were on a series of field trips in western Turkey, I wanted to run a field experiment to test the colonization ability of the land snails in the genus Albinaria. My bright idea was to introduce the local species to areas where they did not exist to determine if they would form long-term colonies and also to determine if 2 species coexisting at the same spot would hybridize. Initially, Tim resisted to the idea of moving species to places where they did not exist, but eventually agreed to help me with the experiment after I argued that the locations of introduction would be within the ranges of the species and that their topographical characteristics would prevent the spread of the snails beyond a few tens of meters.

The 2 Albinaria species we worked with were A. caerulea and A. lerosiensis. And one of the 2 localities we picked for the test was a low hill of limestone rocks*. The marshy plain surrounding the hill provided an effective barrier against the spread of the snails beyond the hill. Albinaria lerosiensis already existed on the hill. All we did was plant a handful of live, but dormant A. caerulea, originally from about 10 km away, at a spot on the hill. I then took pictures of the release spot and recorded its coordinates.

Our initial plan was to return within a year or 2 to see how the introduced A. caerulea was doing. But even though I went back to Turkey in 2007 and 2008, I did not have a chance to go to the test area. Finally, on a hot and sunny day this past June, I climbed up the hill with my GPS receiver in hand. Soon I reached the release area, but could not recognize the exact spot until I took out a pictureof the spot I had brought with me and started comparing the rock formations around me to those in the picture.

Here is what the release spot looked like on 3 July 2006. The small pile of rocks in the foreground was meant to be a long-term marker.

And here is the same spot almost exactly 4 years later. The rock pile had disappeared.

I did not see any live Albinaria, which estivate on rock surfaces and are, therefore, easy to spot. But there were many empty shells, all of which I collected. Most were of A. lerosiensis, but a few, including one juvenile, belonged to A. caerulea. All of the snails we had introduced were adults; so the juvenile shell meant that some reproduction of the introduced species had taken place. But the lack of live snails is preventing me from making any definite conclusions for the time being.

The experiment is still running. I plan to return to both release sites in the future.

*The other spot was a cemetery about which I may write in a future post.

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