Illuminating protist diversity in pitcher plants and bromeliad tanks

Many species of plants have evolved structures called phytotelmata that store water and trap detritus and prey. These structures, some more specialized for carnivory than others, house diverse communities of organisms: the inquiline microbiome, that aids breakdown of litter and prey. The invertebrate and bacterial food webs in these systems have been well characterized, but less is known about microbial eukaryotic community dynamics. Using small subunit rDNA amplicon sequencing from repeated temporal and geographic samples of wild and cultivated plants across the Northeast U.S.A., we demonstrate that communities are variable within and between host plant type. Across habitats, communities from tropical bromeliads grown in a single room of a greenhouse were nearly as heterogeneous as wild pitcher plants spread across hundreds of kilometers. At the scale of pitcher plants in a single bog, seasonal patterns govern protist community structure, with variable spring communities transitioning to more homogeneous communities that resemble the surrounding habitat. Our results indicate that protist communities in phytotelmata are variable, likely due to stochastic founder events and colonization/competition dynamics leading to tremendous heterogeneity.