Location: Crop Bioprotection Research
Project Number: 5010-22410-020-01-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2018
End Date: Jun 30, 2019
1. Determine how the assembly of a common grazer’s gut microbiota is driven by the corresponding assembly of the invertebrate food web. 2. Determine how microbiome–driven differences in the growth rate of community members influence invertebrate community assembly.
The invertebrate communities inhabiting storm water basins, detention basins and retention ponds will be sampled weekly during the ice-free season for a period of three years. During each sampling occasion, the physical and chemical characteristics of each habitat will be quantified using standard water quality meters. The invertebrate communities will be identified to the lowest possible taxonomic unit using taxonomic keys. Mosquito larvae from each habitat and sampling period will be counted and DNA will be extracted from a sample of 10-20 larvae from each habitat and time point and their midgut microbial communities characterized using high-throughput sequencing system. Water samples will also be collected from each habitat and their microbial communities compared with those of mosquito midguts. In addition to field surveys, we will also establish 32 experimental food webs (4 invertebrate assemblages x 4 microbial assemblages x 2 invasion orders) to test hypothesis that community assembly of the eukaryotes influences the assembly of the larval gut microbial assembly. These food webs will vary in (1) food web complexity (Culex only, Culex plus competitor, Culex plus predator, Culex plus competitor and predator), (2) microbial assemblage (grass infusion, grass infusion + antibiotics, grass infusion + nutrients, grass infusion + nutrients and antibiotics) and (3) invasion order (Culex eggs added on day 1, Culex eggs added on day 4). The different food web assemblages will allow us to assess the relative importance of competitors, predators and trophic cascades on the free-living microbial assemblages. The difference in timing of invasion order for Culex (day 0 versus day 4) provides us with an opportunity to explore how priority effects in the invertebrates may influence larval gut colonization. Together, these treatments will allow us to determine the relative importance of bottom up effects provided by the baseline microbial assemblages and the potential for competition, predation, trophic cascades and priority effects within the invertebrates to influence the free-living microbes available to colonize the larval guts. DNA will be extracted at the PIs institution and shipped to ARS for high-throughput sequencing. We will use multiple laboratory experiments to quantify how differences in larval gut microbiomes can influence larval growth and survival. As a first step, all mesocosms will be fitted with emergence traps and all surviving mosquitoes will be collected at emergence and killed. Survival during the larval stage, time to emergence, and body size (based on wing-length) will be collected. These data, in combination with the larval microbiome collected in project 1, will allow us to assess the role of various foodweb aspects on larval mosquito growth and survivorship. The adult body size information will be used to model treatment effects on adult fitness.