A Relationship Between Competition and Sex Ratio of Shadscale

Abstract

The sex ratio of shadscale populations within and outside grazing exclosures show significant departures from random expectations. Males are over represented within the ungrazed exclosures, while females are more prevalent in the grazed pastures. These unequal sex ratios could be the result of three factors: differences in genetic composition, differential grazing pressure on males and differences in water stress. Due to the increased plant cover within the ungrazed exclosures, we believe that plants inhabiting these sites are under greater water stress. Moreoever, it appears that females either tolerate water stress less well than males or change sex when stressed.