Determinants of host-associated trait distribution in Ascomycete marsh endophytes

Background/Question/Methods

Ascomycete endophytes inhabit plant tissue where they perform many metabolic, physical, and chemical processes important to plant physiology and ecology such as growth factor production, nutrient solubilization, and pathogen repression. However, it is unclear what factors influence the distribution of these functional processes among endophytes. Previous work has identified phylogenetic relatedness, environmental stress, and host plant association as important factors mediating trait distribution. We have evaluated the host-associated functional characteristics of 53 root endophyte taxa native to Louisiana marshes in order to test which factors (relatedness, environment, or host association) influence trait distribution in this system. We hypothesize that closely related endophytes will possess similar functional profiles and that endophytes sourced from higher stress environments or stress-tolerant hosts will display more beneficial characteristics. To test this we use ANOVAs, mixed models, and principal components analysis.

Results/Conclusions

In general, traits are distributed independently. Host associated traits differ widely in their distribution. We found 58% of tested endophytes to inhibit pathogens, 49% to solubilize nutrients, and only 4% to produce a plant auxin. Moreover, we have found modest evidence for trait conservation at the genus level, though this trend is less true at higher levels of organization. In addition, trait conservatism is greatest when evaluated according to a presence/absence regime and is less apparent when comparing different magnitudes of trait expression.