Entomologica Romanica Vol. 21 / 2017
2017
Table 1. Number of individuals of Biston betularia forms in the year 1987 and 2012 dominant in 1987, reaching 100%, whereas in 2012 the percentage of the black carbonaria form had declined drastically (60%), the intermediates insularia is 35% and we encounter even the black and white typica form (Fig. 1). The decline of the carbonaria form is also found in the medium polluted forest stands, where the insularia form was the most common in 2012 (Fig. 2). Percentages of the melanic forms in medium and unpolluted sites are very similar, in the past and now. Comparing the overall situation between 1987 and 2012, the insularia form is dominating now; percentages of 75% and 80% were recorded in the medium and unpolluted sites. In the medium damaged stands only half the percentage of carbonaria can be found in 2012 and in the unpolluted sites the percentage of carbonaria decreased by 33% (Fig. 3). The typica form specimens are absent in 2012 in the medium polluted sites; this might be an effect of natural selection and also low trapping success. It should be mentioned that the insularia form specimens are morphologically diverse; we can encounter individuals that resemble with typica form and specimens with the carbonaria form. The decline of carbonaria was encountered in Britain and North America where measures to prevent the atmospheric pollution had been taken (Clarke and Sheppard 1966, Grant et al. 1998). The pollution levels from Copșa Mică area had been gradually decreasing after 2009 when the nonferrous plant SOMETRA was closed; this led to changes to the vegetation. The occurrence of melanic forms in the Copșa Mică area can be explained according to some authors to gene flow (Lees and Creed 1977); others linked rise and fall of melanic forms from Britain and America with the increase and decrease of atmospheric pollution (Grant 1999, Grant and Wiseman 2002). Predation has a substantial role in the decline of melanic forms in the post-industrial areas, the melanic moth being selectively eaten by birds given the fact that they are more visible on the trunks of the trees (Cook and Turner 2008, Cook et al. 2012, Cook and Saccheri 2013, vanT Hof et al. 2013, vanT Hof et al. 2016, Eacock et al. 2017). Conclusions Our data indicate a decline of the carbonaria form in the Copșa Mică area. Used as a bioindicator in the past, this decline suggests that the pollution level is lower now, and the health of the forest habitats has improved. The insularia form, which is independent of the pollution level (Rákosy and Rákosy 1997), is more frequent in 2012. Probably, the carbonaria form will continue to decline in the future and the typica form will become more abundant; additional research is needed to prove this hypothesis. Aknowledgements The authors would like to thank the anonymous referees for improving the preliminary manuscript and for their useful comments. We are grateful to Ilik Saccheri for linguistic corrections and for his constructive comments on the earlier version of this manuscript. Special thanks to Petre Crețu, Nicolae Crețu, Elena Törők and Cornel Törők for their help during fieldworks. This work was possible with the financial support of the Sectoral Operational Programme for Human Resources Development 2007- 2013, co-financed by the European Social Fund, under the project number POSDRU/107/1.5/S/76841 with the title „Modem Doctoral Studies: Internationalization and Interdisciplinary”. References Barbu C.H. (2006) Preliminary study. Screening assessment of the existing data and studies concerning the Copșa Mică industrial area. Proposal of actions to be taken for the accurate determination of the degree of pollution and estimated costs, Lucian Blaga University of Sibiu Publishing House, Sibiu, Romania. Cook L.M. and Turner J.R.G. (2008) Decline of melanism in two British moths: Spatial, temporal and interspecific variation. Heredity 101: 483-489. Cook L.M. and Saccheri I. J. (2013) The peppered moth and industrial melanism: evolution of a natural selection case study. Heredity 110: 207-212 Cook L.M., Grant B.S., Saccheri I.J. and Mallet J. (2012) Selective bird predation on the peppered moth: the last experiment of Michael Majerus. Biology Letters 8 (4): 609-612. Clarke C.A. and Sheppard P.M. (1966) A local survey of Unpolluted sites 19877 20121 3 16 6