What was done
Working with Drosophila subobscura flies -- which they collected from a swampy area on the bank of the Danube river near the town of Apatin, approximately 200 km northwest of Belgrade, Serbia -- the authors analyzed inversion polymorphisms in them, comparing their results (from 2008 and 2009) with results obtained from flies collected at the same site in June 1994, because, as they put it, "genes located within inversions are associated with a variety of traits including those involved in climate adaptation," citing Hoffmann and Rieseberg (2008) in this regard.

What was learned
Zivanovic and Mestres determined there was a significant increase in the frequency of certain chromosomal arrangements characteristic of southern latitudes, which they describe as "warm adapted," and a significant decrease in the frequency of such arrangements characteristic of northern latitudes, which they describe as "cold adapted."

What it means
The two researchers say their observations suggest they have detected "the effect of selection on chromosomal polymorphism composition," and, therefore, that "some form of natural selection appears to be acting as a reaction to the increase in temperature associated with [the] many heat waves that have markedly affected the Balkan Peninsula," especially over the past decade and a half. They also note that their results "agree with those from southwestern and central European populations (Rodriguez-Trelles and Rodriguez, 1998; Sole et al., 2002; Balanya et al., 2004, 2006, 2009)." In addition, they note that similar things have been observed in D. melanogaster in Australia, citing Anderson et al. (2005) and Umina et al. (2005), and in D. robusta in North America, citing Levitan and Etges (2005). In fact, they report that "the climate change of recent decades has led to heritable genetic changes in animal species as diverse as birds, squirrels and mosquitoes (Bradshaw and Holzapfel, 2006)." Thus, it would appear that many forms of animal life may be well equipped to evolve with sufficient rapidity to survive the challenges of rapid global warming.

References
Anderson, A.R., Hoffmann, A.A., McKechnie, S.W., Umina, P.A. and Weeks, A.R. 2005. The latitudinal cline in the In(3R) Payne inversion polymorphism has shifted in the last 20 years in Australian Drosophila melanogaster populations. Molecular Ecology 14: 851-858.

Balanya, J., Sole, E., Oller, J.M., Sperlich, D. and Serra, L. 2004. Long-term changes in the chromosomal inversion polymorphism of Drosophila subobscura. II. European populations. Journal of Zoological Systematics and Evolutionary Research 42: 191-201.

Balanya, J., Oller, J.M., Huey, R.B., Gilchrist, G.W. and Serra, L. 2006. Global genetic change tracks global climate warming in Drosophila subobscura. Science 313: 1773-1775.

Balanya, J., Huey, R.B., Gilchrist, G.W. and Serra, L. 2009. The chromosomal polymorphism of Drosophila subobscura: A micro evolutionary weapon to monitor global change. Heredity 103: 364-367.

Bradshaw, W.E. and Holzapfel, C.M. 2006. Evolutionary response to rapid climate change. Science 312: 1477-1478.

Hoffmann, A.A. and Rieseberg, L.H. 2008. Revisiting the impact of inversions in evolution: From population genetic markers to drivers of adaptive shifts and speciation? Annual Review of Ecology, Evolution, and Systematics 39: 21-42.

Levitan, M. and Etges, W.J. 2005. Climate change and recent genetic flux in populations of Drosophila robusta. BMC Evolutionary Biology 5: 10.1186/1471-2148-5-4.

Rodriguez-Trelles, F. and Rodriguez, M.A. 1998. Rapid microevolution and loss of chromosomal diversity in Drosophila in response to climate warming. Evolutionary Ecology 12: 829-838.

Sole, E., Balanya, J., Sperlich, D. and Serra, L. 2002. Long-term changes in the chromosomal inversion polymorphism of Drosophila subobscura. I. Mediterranean populations from southwestern Europe. Evolution 56: 830-835.