Background/Question/Methods The emerging field of community genetics is dependent upon the demonstration of heritable and repeatable community phenotypes in which related individuals can be shown to support similar communities of organisms. In an experimental forest with replicated clones of a foundation tree species (narrowleaf cottonwood, Populus angustifolia), we quantified a community of 103 arthropod species representing multiple trophic levels. By conducting studies over 3 years, we also examined how plant genotype might affect community stability (i.e., species turnover rates over time).

Results/Conclusions Four major patterns emerged: 1. Both field and common garden studies showed that individual tree genotypes supported different communities. 2. We found significant broad-sense heritability for community composition (H²_C = 0.66), species richness (H²_C = 0.31), abundance (H²_C = 0.36), and stability (H²_C = 0.32). 3. As a possible mechanism for our stability findings, we found that the abundance of a common insect herbivore and arthropod species richness of individual tree genotypes were both significantly correlated with increased community stability. 4. Broad-sense heritability of community composition was highly repeatable and over three consecutive years ranged from H²_C = 0.63 to 0.68. These findings demonstrate that the genetics of a foundation tree species can structure a diverse community of arthropods. Our findings of significant community heritability, repeatability, and stability represent an important advance in understanding the genetic components of community structure, which have evolutionary and conservation implications.