Predator dispersal influences predator distribution but not prey diversity in pitcher plant microbial metacommunities

Abstract

The spatial distribution of predators can affect both the distribution and diversity of their prey. Therefore, differences in predator dispersal ability that affect their spatial distribution, could also affect prey communities. Here, we use the microbial communities within pitcher plant leaves as a model system to test the relationship between predator (protozoa) dispersal ability and distribution, and its consequences for prey (bacteria) diversity and composition. We hypothesized that limited predator dispersal results in clustered distributions and heterogeneous patches for prey species, whereas wide predator dispersal and distribution could homogenize prey metacommunities. We analyzed the distribution of two prominent bacterivore protozoans from a 2‐year survey of an intact field of Sarracenia purpurea pitcher plants, and found a clustered distribution of Tetrahymena and homogeneous distribution of Poterioochromonas. We manipulated the sources of protozoan colonists and recorded protozoan recruitment and bacterial diversity in target leaves in a field experiment. We found the large ciliate, Tetrahymena, was dispersal limited and occupied few leaves, whereas the small flagellate Poterioochromonas was widely dispersed. However, the bacterial communities these protozoans feed on was unaffected by clustering of Tetrahymena, but likely influenced by Poterioochromonas and other bacterivores dispersing in the field. We propose that bacterial communities in this system are structured by a combination of well dispersed bacterivores, bacterial dispersal, and bottom‐up mechanisms. Clustered predators could become strong drivers of prey communities if they were specialists or keystone predators, or if they exerted a dominant influence on other predators in top‐down controlled systems. Linking dispersal ability within trophic levels and its consequences for trophic dynamics can lead to a more robust perspective on trophic metacommunities.

Trophic interactions in microbiomes influence plant host population size and ecosystem function

“…Using epifluorescence microscopy [39,40], 52 000 and 24 000 virus-like particles per ml were detected in microbiome sources 1 and 2, respectively. Note that the concentration of virus-like particles in duckweed microbiomes was considerably lower compared to that reported in other studies and in natural microbiomes [36,41]. Due to insufficient viral genetic material, we did not characterize the phages in the microbiome sources.…”

Dispersal and eco-evolutionary dynamics in antagonistic species interactions

“…For natural populations, such multitrait data could be combined with classic field surveys as well as with recent phylodynamic techniques to infer links between spatial structure, dispersal and eco-evolutionary processes [102,[105][106][107]. Alternatively, for sufficiently small organisms, theory can be complemented with laboratory microcosm experiments, in which organisms can disperse naturally [87,[108][109][110][111] and where the spread of infection and evolution can be tracked over longer time scales.…”

Trophic interactions in microbiomes influence plant host population size and ecosystem function

“…While both being bacterivorous consumers, bacteriophages and protozoa may exhibit distinct impacts on microbiomes as microbial parasites vs. predators [24,[26][27][28]. For instance, these two types of consumers may show considerable variation in diet breath.…”

“…Despite the prevalence and significance of microbial bacterivorous consumers in plant microbiomes, little is known about how they impact microbiomes and how the impacts translate into changes in plant populations and ecosystem functions. Specifically, while bacteriophages and protozoa have been studied separately [23, 26, 28, 29], their influences on plant hosts and ecosystem functions have not been directly compared.…”