To evaluate relationships among populations, phenotypic variation of morphological characters in one Gutierrezia microcephala and eight Gutierrezia sarothrae populations from New Mexico was quantified and compared with variation expressed when these same populations were grown in a common garden. During flowering, plants were randomly collected from each population across New Mexico during two growing seasons. A common garden of stem cuttings from these same populations was established in Las Cruces. Vegetative and reproductive characters were measured for each population at original and common sites. Vegetative characters did not differ between G. sarothrae and G. microcephala collected from the same location; however, reproductive characters were dissimilar between these two species. Vegetative and reproductive characters differed among G. sarothrae populations at original and common sites between years, although certain populations clustered. Based on morphological characters, more populations clustered when collected from original sites compared to when grown at the common site. Genetics and environment both played a role in the expression of G. sarothrae phenotype when measuring morphological characters; however, G. sarothrae genotypes maintained their general population phenotype expressed at original sites when grown in the common site. Apparently, vegetative and reproductive characters are fairly stable, and the Gutierrezia genotype has more influence on resulting phenotype than the environment in which it grows.
Nomenclature: Gutierrezia sarothrae (Pursh) Britt. & Rusby GUESA, broom snakeweed; Gutierrezia microcephala (DC.) Gray GUEMI, threadleaf snakeweed.