Estimating the population size and distribution of the Arapahoe snowfly (Arsapnia arapahoe) (Plecoptera: capniidae) along the northern Front Range of Colorado
Date
2015
Authors
Belcher, Thomas Paul, III, author
Kondratieff, Boris, advisor
Vieira, Nicole, committee member
Coleman, Robert, committee member
Fairchild, Matthew, committee member
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Abstract
The population size and geographic distribution of the recently described Arapahoe snowfly, Arsapnia arapahoe (Nelson and Kondratieff) (Plecoptera: Capniidae) is unknown. Prior to this study, A. arapahoe was known only from two tributaries of the Cache la Poudre River in Larimer County, Colorado, Young Gulch and Elkhorn Creek. The objectives of this study were to determine the distribution of A. arapahoe along the northern Front Range of the Rocky Mountains in Colorado, to estimate the abundance of adult A. arapahoe in Elkhorn Creek (the stream with the largest known population), and to identify co-occurring sympatric species as possible surrogate indicators of its presence. I also investigated the potential effects of wildfire and flood disturbance on known populations of the Arapahoe snowfly. To determine the distribution in other Front Range streams, I sampled 54 streams for A. arapahoe in 2013 and 2014, several of which were chosen based on GIS modeling for potential suitable habitats. I also conducted an intensive depletion sampling study in three 300-m segments of Elkhorn Creek (n=5 reaches per segment) using quantitative beat sheet techniques. Sampling was estimated to capture over 90% of available adult individuals, and 100% of A. arapahoe individuals. Thus population size estimates could be obtained. Further, adults of A. arapahoe were only discovered in six additional, first-order streams outside the original type localities in Cache la Poudre River Basin. New species localities were discovered in three additional drainage basins: Big Thompson River, St. Vrain River, and Boulder Creeks. Intensive sampling efforts in Elkhorn Creek revealed substantially low abundances of A. arapahoe adults (only 10 individuals found in the duration of the study), justifying the designation of this species as a rare taxon. Two sympatric species, A. decepta (Banks) and Capnia gracilaria Claassen, were consistently found with A. arapahoe, and thus may serve as a future indicator of suitable stream habitat. Both A. arapahoe and associated species appeared to be adversely impacted by post-wildland fire erosion and sediment deposition; however, capniids, including A. arapahoe, appeared to be resilient to flooding. I present suggestions for continued monitoring of the presence, abundance and distribution of A. arapahoe for conservation of this rare and endemic Colorado stonefly.
Description
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Subject
Arsapnia arapahoe
Capnia
ecology
aquatic insect
winter stonefly