Host Plant Traits and Site History Shape Root Fungal Endophytic Communities of Sporobolus spartinae After Long-Term Exposure to Contaminants

Root fungal endophytes (fungi inhabiting the inside of root cells without any apparent harm) are widely recognized as important symbionts of host plants, providing benefits to the host plant such as water and nutrient acquisition. While endophyte communities are often subject to the influence of plant hosts, abiotic factors such as long-term and continuing exposure to heavy metal (HM) contaminants can also exert as much influence as the hosts. Herein, we investigated the relative influences of host plant traits against the backdrop of on-going HM exposure (i.e., Ba, Pb, and As) on the root fungal endophytes of Sporobolus spartinae, a dominant grass in the prairie dunes in barrier islands of South Texas, USA. We characterized fungal communities of plants growing in a contaminated environment versus those in a habitat with no known history of contamination using high throughput sequencing of the Internal Transcribed Spacer (ITS) region. We found that host plant traits exert significant influences on the overall fungal diversity though not as strong as the legacies of HM exposure. Plants in the contaminated site harbored more diverse and distinct root fungal communities than plants in non-contaminated environment. Aboveground plant traits (e.g., aboveground biomass, specific leaf area) exert stronger influence than root traits on fungal diversity. These findings allude to the persisting effects of contamination on fungal endophytic communities and that their responses can potentially be mediated by host plants over time. Our results additionally indicate the importance of accounting for host-endosymbiont interactions in determining organismal responses to environmental disturbances.