Diversity of surface active invertebrate communities at the DePauw Nature Park and Arboretum
Aaron Randolph, Science Research Fellow
in collaboration with Bryan Helm, David Pope, Vanessa Fox, and Dana Dudle
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Abstract:Until recently there haven’t been any data available about the compositions of either the vegetation or the surface active invertebrates (SAIs) in the Nature Park or Arboretum. My project focuses on describing the composition of the SAI community and examining the relationships between the SAI community and habitat characteristics at the sites. I hypothesized that composition of SAI communities will differ relative to habitat characteristics at the sites. Pitfall traps were constructed using 16-oz plastic cups, propylene glycol, chicken wire, and masonite, and were placed in each of three forested sites: Quarry Hillside (QH), Quarry South (QS), and the Arboretum (ARB). Traps were placed at 30m intervals along 3 parallel transects. The captured SAIs were sorted, identified to order, and counts were completed for 30 traps in QH, 30 in QS, and 15 in the ARB. We sampled vegetation at ten randomly chosen plots within each forested site and vegetation diversity and structure were compared across sites using one-way ANOVAs. We calculated mean trap efficiency (SAIs per trap per day) for each site, and calculated a Shannon Diversity index, which measures taxonomic diversity and evenness, for each site. Traps were most successful at QS, with the highest number of trap days, highest total number of captures, and highest capture rates. Shannon diversity index for the invertebrate community did not differ between the three sites; however the composition of the invertebrate community differed between the three sites. Traps in the ARB captured a higher percentage of ants and slugs. QH and QS had a higher percentage of millipedes. Capture rates of springtails were highest at QS and captures of crickets and spiders were highest at QH. Differences in capture rates and community composition may be due to differences in forest structure and habitat features. For example, lower leaf litter and higher understory vegetation cover at QS may have contributed to higher captures of invertebrates overall, possibly because the SAIs had more mobility throughout the forest . Issues encountered in this specific project include the large number of destroyed and disturbed traps, especially at the Arboretum. This issue could probably addressed by hiding traps under nearby low lying brush. Also, invertebrates were identified to order. Identification to species might be a better indicator of the invertebrate diversity.