Community heritability, repeatability and stability of a dominant tree species: from the common garden to natural stands

Background/Question/Methods

Recent studies have shown a strong plant genetic component to associated community structure, but have not shown if the effects are consistent and repeatable across years.  If communities are both heritable and repeatable (i.e., similar communities assembling on the same genotypes annually), then plant genetics may also affect community properties previously thought to be emergent such as ‘stability’.  Using replicated clones of narrowleaf cottonwood (Populus angustifolia) in a common garden and naturally occurring stands we examined a large arthropod community and found similar patterns of community stability.

Results/Conclusions

In a common garden we found that: 1. Individual tree genotypes supported significantly different arthropod communities.  2.  These findings were highly repeatable over 3 consecutive years (r = 0.91) indicating that community responses to individual tree genotypes are consistent from year-to-year.  3. Differences among tree genotypes in community stability (i.e. community similarity across years) were found to be heritable (H²_C = 0.32). 4. There was a positive correlation between diversity (i.e. species richness) and community stability. In naturally occuring stands we found that: 1. Diversity and stability were again positively correlated. 2. Similar to our common garden results, the abundance of a foundation herbivore (Pemphigus betae) was again positively correlated with community stability . 3. Increasing genetic variation among stands tended to show increasing levels of community stability. By demonstrating significant community heritability, repeatability, and a genetic component to community stability in a common garden while also finding similar results in natural stands argues that the study of whole communities and emergent properties such as community stability can be advanced within a genetic/evolutionary framework.