Indirect genetic effects of rhizobium symbiosis plasmid on legume-grass dynamics

Legume-grass dynamics are keystone interactions in terrestrial ecosystems, but outcomes vary from facilitative to competitive depending on nitrogen (N) availability in the environment. Rhizobial bacteria provide fixed N to their legume hosts, and thus the presence or identity of rhizobia can influence host interactions with other species. In Rhizobium symbionts of clover, the genes that determine symbiosis compatibility and efficiency are located on a plasmid (pSym, or symbiosis plasmid), which can be shared within and across taxa through horizontal gene transfer (HGT). Previous work has identified four distinct clades of pSyms that control partner quality variation in a natural population of Rhizobium. If legumes facilitate grass productivity, then these facilitative effects of clovers on grasses might be heighted when clovers are associated with higher quality rhizobium. To investigate how this plasmid variation might affect legume-grass dynamics, we inoculated experimental mesocosms of mixed clover and grass with one of four treatments: rhizobia with high-quality pSym clade A, rhizobia with low-quality pSym clade C, rhizobia lacking the pSym, or no rhizobia (mock inoculation). We demonstrate that variation in the Rhizobium pSym impacts grass productivity and legume-grass dynamics. Specifically, in mesocosms with high quality rhizobium (pSym-type A) increase grass aboveground biomass. This study indicates potential for rapid evolution via HGT in bacterial communities to have indirect effects on other species via their symbiosis with legumes.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Plant Biology

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Belloso, Erica Natalie

Contributors dc:contributor

• Heath, Katy D
• Lau, Jennifer
• Yannarell, Anthony

• Ecology, Evolution

Statement dc:rights

• Copyright 2025 Erica Belloso

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132713

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132713