Man-made environmental changes affect the boundary between two taxa of Laudakia


Yehudah L. Werner, Department of Evolution, Systematics and Ecology, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel. Tel: +972 2 6585874; Fax: +972 2 6584741


This project tested whether, and how, man-made changes in the environment would affect the boundary between parapatric-related taxa of Laudakia (Reptilia: Agamidae), whose distributions meet at a boundary between ecological regions. Israel is ecologically diverse with a mesic (Mediterranean) north and an arid (Saharo-Arabian) south. The lizard hardun Laudakia stellio is represented in Israel mainly by two subspecies: the Mediterranean Lau. s. ssp. and the desert Lau. s. brachydactyla. These are conventionally distinguished by the key character, number of subdigital lamellae under the fourth toe, visible in museum specimens examined for the purpose. The results revealed that during 1935–1978, the boundary between the two subspecies had shifted 15 km southwards. This is interpreted as resulting from the documented southwards spread of irrigated agriculture. During this time, the average subdigital count of each subspecies near the inter-taxa boundary shifted slightly towards the average of the other subspecies. In each subspecies, in this area, at the same time, the coefficient of variation of the subdigital count increased. The last two processes are interpreted as reflecting reciprocal migration, enhanced by the documented expanded road system and intensified human transportation. Hence, in this case, anthropogenic developments have changed both the location and the genetic structure of the boundary between two parapatric taxa.