The taxonomy, distribution and faunal succession of Buliminus (Pulmonata: Enidae) in Israel

Abstract

The taxonomy, intraspecific variation and distribution of each of the eight Israeli species of the rock-dwelling landsnail Buliminus is described, with a new subspecies labrosus jiftliki. The general biology of the genus is briefly described, and a key to all species and subspecies is given. Intraspecific and interspecific variation is partly associated with different environmental conditions. In the more hot regions of their distribution areas, the snails have a narrow shell, a smaller aperture, a more smooth shell surface and thick lips. The possible adaptive significance of these characteristics in hot regions is discussed. The distribution limits of many species closely coincide with both isohyets and types of substratum, suggesting that rainfall and substratum are the most important physical factors determining distribution. Vegetation in the Mediterranean region could perhaps influence such aspects of the distribution as the choice of northern or southern slopes. It is suggested that in Israel, in each climatic zone and within the limits determined by these physical factors, a faunal succession is today in operation. In the mediterranean, steppe, steppe periphery and arid regions, species which evolved or arrived recently are displacing more ancient elements. As compared with the ancient fauna, the new species have less rigid ecological requirements and are more capable of adjusting themselves to severe environmental conditions by altering their shell proportions. The last relics of the ancient fauna survive in the Judean Hills and along the isohyet 70 mm, on the brim of the extreme desert. In I. labrosus the presence of a reverse cline, in both shell and genitalia, near the borderline with l. spirectinus, and, in addition, the presence along the borderline of a few intermediate individuals, suggests that l. labrosus is “rolling back”l. spirectinus by keeping up a narrow belt of hybridization.