Habitat effects on biased sex ratio of wild Pistachio (Pistacia atlantica subsp. mutica) in Maymand region of Kerman province

The wild Pistachio, Pistacia atlantica subsp. mutica, is belonged to mountain of Irano-Turanian region, and distributed in northwest, northeast, center, east and south of Iran. The sexual identification mechanism of this species is unknown and denotation of gender is impossible until flowering. In this study sex ratio of populations of this dioecious shrub was evaluated by several hypothesis concerning biased sex ratio, in some microhabitates of Maymand region in ShahreBabak of Kerman province. The populations located in microclimatic gradient, such as slope, wind, altitude and edaphic factors display a male-biased sex ratio on stressful microhabitats. We found a significant correlation between biased sex ratio and density of plants too. Low density of plants correlates with a high preponderance of males, but the sex ratio approximately equal when density increases. So we found female preponderance when pollen grain competition exists. As results of this study, mortality of female plants and competition of pollen grain are effective factors in biased sex ration in wild pistachio populations in this region.