EVOLUTION OF WILD SHEEP IN IRAN.

Abstract

The genus Ovis, which includes all true sheep, constitutes one of the more complicated mammalian genera relative to its evolution and systematics. Wild sheep presently range from Europe (originally confined to Corsica and Sardinia in the Holocene, but now widely introduced in mainland Europe) through xeric and subxeric regions of the Middle East, Soviet Turkmenistan, the Indian Subcontinent, Central Asia, and Siberia. In North America, wild sheep range from Alaska to northern Mexico. Various authors (Lydekker, 1913; Nasonov, 1923; Tsalkin, 1951; Haltenorth, 1963) have recognized from one to nine species. A major obstacle in clarifying the systematics of Ovis arises from the diverse phenotypic variability exhibited throughout its wide Holarctic distribution. Iran, perhaps, presents the most complicated area relative to the evolution of wild sheep. Wild sheep occur throughout Iran except in forest, tall grass, and tall shrub regions; the animals prefer open, undulating montane habitat. In no other known area of comparable size do wild sheep exhibit as much phenotypic and chromosomal variation. Early authors (Lydekker, 1913; Nasonov, 1923) recognized three species in Iran. Recent studies (Nadler et al., 1971, 1973a) in northern Iran have greatly clarified the systematics of wild sheep in this area. They revealed the existence of two cytologically distinct populations with diploid (2N) chromosome numbers of 58 in northeastern Iran and 2N = 54 in northwestern Iran. Where these cytotypes converged in the Alborz (Elburz) Mountains of northern Iran, a hybrid zone existed with numerically heterogeneous karyotypes of 2N 54, 55, 56, 57 and 58. This paper further describes the chromosomes of wild sheep from the hybrid zone of the Central Alborz Mountains originally described by Nadler et al. (1971) and from other populations of wild sheep in southern Iran. In addition serological, morphological, ecological, and reproductive data are related to chromosomal characters and these lines of evidence are combined to clarify further the evolution of Iranian wild sheep.