Phenotypic Variation
Consistent with our first hypothesis, we found significant within and
among population variation for traits at each of the three common
gardens (Table 1, Fig. 3), with phenology traits exhibiting higher
differentiation at the population than the genotype level in all but one
case. For example, most of the variation in bud flush in Yuma and Agua
Fria was explained by population. For the morphological and growth
traits, the relative contribution of population vs. genotype varied
among gardens. Traits measured in the hottest common garden exhibited
stronger population than genotype effects in four out of the five traits
(SLA had a higher genotype variance). This garden thus produced higher
values of QST (the proportion of the genetic variance
that is found among rather than within populations, see next section).