DISSERTATION RESEARCH: Temporal Sampling and DNA Metabarcoding to Test the Climate Variability Hypothesis

Colorado State University, Fort Collins CO

Investigators

Abstract

The Climate Variability Hypothesis (CVH) proposes that the range of temperatures species can tolerate increases with the annual range of temperatures they have experienced over evolutionary time. Climate variability increases with latitude and thus it is expected that temperate species will have wider thermal tolerances, higher dispersal ability, and wider distributions than tropical species. Researchers previously asked if temperate mountain stream insects from Colorado have larger elevation range sizes than tropical species from Ecuador; however, range sizes could only be estimated for common species and specimens could only be collected once. To strengthen this work, stream insects will now be sampled over time (temporal sampling) and a DNA approach will be used to identify all species (common and rare). Temporal sampling will allow researchers to track species' elevational positions as they drift from higher to lower elevations over time. Because the flow of water constantly pushes larvae downstream and temperate larvae spend more time in stream, temperate zone larvae are expected to drift farther downstream during development than tropical species. This work will allow researchers to detect previously overlooked rare species. These advances strengthen an already extensive test of the CVH by incorporation of species movement and rare species into estimates of distributions of elevation range sizes. Results of this work will provide information about how natural selection resulting from climate variability influences species dispersal ability and range sizes with general implications for understanding speciation and the evolution of biodiversity. Larval aquatic insects will be collected 6 times over a yearlong period from streams located along transects from ~1500-3500m in the Colorado Rocky Mountains and the Ecuadorian Andes (11 sites at each latitude). On each sampling date at each site, insects will be collected for 5 minutes from all microhabitats within a 100m stream reach using a D-frame net. Samples will be preserved in ethanol and insects will be separated from sediment and detritus. For each sample, all insect tissue will be homogenized and DNA will be extracted and purified using commercially available kits. The animal DNA barcoding gene, Cytochrome c Oxidase subunit I (COI), will be PCR amplified. Full-length DNA barcodes will be generated by shotgun sequencing and assembly of COI amplicons using next-generation sequencing on an Illumina platform. DNA barcodes will be queried against a regional reference library to determine the composition of samples, re-estimate elevation range sizes for taxa, and compare range sizes and dispersal ability among latitudes.