Assembly of pitcher plant microbiomes 2016

Aim Ecological theory suggests that dispersal limitation and selection by
climatic factors influence bacterial community assembly at a continental
scale, yet the conditions governing the relative importance of each
process remains unclear. The carnivorous pitcher plant Sarracenia purpurea
provides a model aquatic microecosystem to assess bacterial communities
across the host plant's North–South range in North America. This
study determined the relative influences of dispersal limitation and
environmental selection on the assembly of bacterial communities
inhabiting S. purpurea pitchers at the continental scale. Location Eastern
United States and Canada. Time period 2016 Major taxa studied Bacteria
inhabiting S. purpurea pitchers. Methods Pitcher morphology, fluid,
inquilines and prey were measured, and pitcher fluid underwent DNA
sequencing for bacterial community analysis. Null modeling of β-diversity
provided estimates for the contributions of selection and dispersal
limitation to community assembly, complemented by an examination of
spatial clustering of individuals. Phylogenetic and ecological
associations of co-occurrence network module bacteria was determined by
assessing the phylogenetic diversity and habitat preferences of member
taxa. Results Dispersal limitation was evident from between-site variation
and spatial aggregation of individual bacterial taxa in the S. purpurea
pitcher system. Selection pressure was weak across the geographic range,
yet network module analysis indicated environmental selection within
subgroups. A group of aquatic bacteria held traits under selection in
warmer, wetter climates, and midge abundance was associated with selection
for traits held by a group of saprotrophs. Processes that increased
pitcher fluid volume weakened selection in one module, possibly by
supporting greater bacterial dispersal. Conclusion Dispersal limitation
governed bacterial community assembly in S. purpurea pitchers at a
continental scale (74% of between-site comparisons) and was significantly
greater than selection across the range. Network modules showed evidence
for selection, demonstrating that multiple processes acted concurrently in
bacterial community assembly at the continental scale.