Drivers and patterns of microbial community assembly in a Lyme disease vector

Abstract

Vector-borne diseases constitute a major global health burden and are increasing in geographic range and prevalence. Mounting evidence has demonstrated that the vector microbiome can impact pathogen dynamics, making the microbiome a focal point in vector-borne disease ecology. However, efforts to generalize preliminary findings across studies and systems and translate these findings into disease control strategies are hindered by a lack of fundamental understanding of the processes shaping the vector microbiome and the interactions therein. Here, we use 16S rRNA sequencing and apply a community ecology framework to analyze microbiome community assembly and interactions in <i>Ixodes pacificus</i>, the Lyme disease vector in the western United States. We find that vertical transmission routes drive population-level patterns in <i>I. pacificus</i> microbial diversity and composition, but that microbial function and overall abundance do not vary over time or between clutches. Further, we find that the <i>I. pacificus</i> microbiome is not strongly structured based on competition but assembles nonrandomly, potentially due to vector-specific filtering processes which largely eliminate all but the dominant endosymbiont, <i>Rickettsia</i>. At the scale of the individual <i>I. pacificus</i>, we find support for a highly limited internal microbial community, and hypothesize that the tick endosymbiont may be the most important component of the vector microbiome in influencing pathogen dynamics.