Top-Down Processes Drive Taxonomic and Phylogenetic Diversity in a Model Aquatic Microbial Community

Area of Science:

• Ecology
• Microbial Ecology
• Aquatic Ecology

Background:

• Understanding aquatic microbial community responses to bottom-up and top-down ecological processes is crucial but remains poorly understood.
• Previous studies often focus solely on taxonomic diversity, neglecting other diversity metrics like phylogenetic diversity.

Purpose of the Study:

• To investigate the influence of bottom-up and top-down processes on bacterial taxonomic and phylogenetic diversity within the Sarracenia purpurea model aquatic food web.
• To assess the role of Wyeomyia smithii mosquito larvae as a potential keystone predator in structuring bacterial communities.

Main Methods:

• Experimental manipulation of resource levels and Wyeomyia smithii abundance in the Sarracenia purpurea system.
• Assessment of bacterial communities using high-throughput sequencing of 16S rRNA genes.
• Analysis of multiple components of taxonomic and phylogenetic alpha- and beta-diversity.

Main Results:

• Mosquito larvae predation decreased taxonomic alpha-diversity but did not affect it based on predator number or resource level.
• Phylogenetic alpha-diversity responses varied depending on the metric used.
• Both taxonomic and phylogenetic beta-diversity increased due to mosquito larvae predation, with some influence from resource level and predation intensity.

Conclusions:

• Wyeomyia smithii larvae exert strong top-down control on bacterial taxonomic and phylogenetic diversity in Sarracenia purpurea, but do not function as a keystone predator.
• Predation by W. smithii alters phylogenetic diversity by removing less abundant lineages, influencing both alpha- and beta-diversity.
• The study underscores the importance of employing multiple diversity metrics in ecological studies of bottom-up and top-down processes.