PARENT SESSION
Poster Session 36: Genetics / Population Ecology
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Variation of Joshua Tree Morphology among Populations in the Eastern Mojave Desert.
Valentovich, Tracy *,1, Sandquist, Darren1, 1 California State University, Fullerton, Fullerton, CA, United States
ABSTRACT- The current distribution of Yucca brevifolia Engelm. (Joshua Tree) is restricted to specific habitats at higher elevations in the Mojave Desert. This distribution warrants investigation because it may represent the result of post-glacial migration and potentially restricts gene flow. The overall objective of our study is to reconstruct the phylogeography of Y. brevifolia based on morphological and genetic variances of populations in the Mojave Desert. Some taxonomic treatments of this species define more than one variety or subspecies based on morphology. This includes Y. brevifolia var. jaegeriana (McKelvey, 1932), a variety of the Eastern Mojave defined by short, stout stems and short leaf lengths. In a preliminary study we examined the morphology of four populations in this region. The morphological variance of these populations was expected to be minimal, because they occurred relatively close to one another and within the described jaegeriana distribution. Trunk sizes and leaf lengths were compared among populations using ANOVA, and a broader evaluation was based on a multivariate analyses of 13 tree and leaf traits. Tree sizes and leaf characteristics of three populations always conformed to the classification of var. jaegeriana; the fourth population (Garnet Mountain, AZ) showed characteristics of var. jaegeriana for leaf traits but not for trunk size. Principle components analysis revealed significant scatter among plants of all populations, but clearly separated the Garnet Mountain population from the rest. These results bring into question the varietal classifications of this species and suggest that environmental factors may cause closely related populations to show notable morphological difference.
Key words: Yucca brevifolia, phylogeography, morphology, Mojave Desert