DANLEY, KIMBERLY, TIFFANY ISAKSEN, NICOLE GARDNER, PAULA RANDALL-YOHO*, AND LOREEN ALLPHIN. Department of Botany and Range Science, Brigham Young University, Provo, UT 84602. - Spatial distribution and sexual dimorphism in dioecious Atriplex garettii Rydb.
Atriplex garrettii Rydb. is a diploid, dioecious member of the
Chenopodiaceae family with a known male specific genetic marker. Sex
determination in this species appears to be genetically controlled
with a 1:1 segregation of sexes. In harsh environments, some species
exhibit a male biased sex ratio. However, A. garrettii
exhibits unbiased sex ratios in its natural populations. This study
assessed whether spatial segregation of sexes occurs within
populations. Other studies have shown that in populations which
exhibit differential spatial distribution of sexes, females prevail in
resource rich microhabitats while males prevail in resource poor
sites. Three populations of A. garrettii, growing in dry,
sandy soils along the Colorado river near Moab, Grand County, Utah,
were assessed for spatial segregation of sexes within populations.
One hundred individuals per population were randomly selected using
the point quarter method. Sex was recorded for all individuals and
their nearest neighbors. Microenvironmental parameters (soil
moisture, soil pH, etc.) were assessed for each sampled individual.
Plant height and foliar crown diameter were measured to determine if
males of A. garrettii are larger than females. Xylem water
potential of each individual was assessed using a pressure chamber to
determine if there was differential water stress in females and males.
Degree of parasitism/pathogenic infection was measured for all
individuals and compared between sexes.
Key words: Atriplex garettii, dioecy, resource allocation, sex ratio, sexual dimorphism, water stress