NATURA MONTENEGRINA, Podgorica, 2013, 12(3-4): 1025-1034 1 ORIGINAL RESEARCH PAPER TEMPORARY PATTERNS OF SPATIAL VARIABILITY IN A HYBRID ZONE OF TWO LAND SNAIL SPECIES FROM GENUS BREPHULOPSIS (GASTROPODA; PULMONATA; ENIDAE) Sergej KRAMARENKO 1 and Igor DOVGAL 2 1 Mykolayiv National Agrarian University, Paryzka Komuna Str., 9, 54020, Mykolayiv, Ukraine. E-mail: KSS0108@mail.ru 2 Schmalhausen Institute of Zoology, B. Khmelnitsky str., 15, 01601, Kiev, Ukraine. E-mail: dovgal@izan.kiev.ua Key words: land snail, Brephulopsis, variability, introgressive hybridization, environmental factors, microevolution. SYNOPSIS The changes of qualitative and quantitative characters in zone of introgressive hybridization of land snails Brephulopsis cylindrica and B.bidens were traced at a period from 1991 to 2009 in the neighbourhood of Simferopol (Crimea, Ukraine). The variability for both groups of characters becomes by unimodal distribution in 2009 which possible concerned with the increasing of the average temperatures in the summer months that observed in the region at a period from 2005 to 2009. It is author’s opinion that in case if such factor changes will be of a periodic nature the pattern of variation in the hybrid zone will also demonstrated periodic changes. On the other hand, if environmental factors will have the unidirectional trend in a long period of time, the elimination of the parent species might observe. In this case the hybridization can be a leading factor in microevolution and speciation. INTRODUCTION The cases of interspecific hybridization have been repeatedly occurred in different mollusks. It was indicated (Schwenk et al., 2008) that for the last 60 years were noted 289 cases of interspecific hybridization in Gastropoda and 323 cases in Bivalvia. It is known that in hybrid zone forming the characteristic clinal gradient of character distribution from predominance of characters of one parental form to another (Brumfield et al., 2001; Dasmahapatra et al., 2002; Seneviratne et al., 2012). However, the temporal aspect of the interspecific hybrid zones operation is scantily known. Thus the changes in morphometric characters of shells in land snail from the genus Cerion in the area of hybridization were studied with an interval of 50 years (Woodruff and Gould, 1987).