Does ungulate herbivore activity affect insect community diversity? The ungulate (exotic Axis and Whitetail deer) populations in Texas Hill Country has exceeded carrying capacity and significantly affected plant species richness and biomass. Little is known how their effects on plants also impacts insect structure and function. The effects of deer herbivory on insect community diversity was tested inside and outside deer exclosures. Previous studies have shown deer herbivory decreases plant species richness and abundance outside exclosures. We hypothesized there would be a corresponding effect on insect community structure. Traditional sweep net and pitfall traps protocol was followed. Insects collected inside four different exclosures (treatment) and four adjacent areas outside (control) exclosures. Each experimental unit had five pitfall traps and was swept once in the morning. The pitfall traps were set in the morning, collected in late evening and again the following morning to assess diurnal and nocturnal active insects. Insects were identified to family and diversity quantified by Shannon Index. Data was collected for six weeks during late spring to midsummer in 2019 during an unusually wet season producing heavy vegetation of forbes and grasses.
Results/Conclusions
Location and collection methods both portray high diversity indices. The sweep method resulted in a higher population, family, and Shannon Index. Sweeping collected 207 insects proving more successful than pitfall trapping collecting only 128 insects. Pitfall trap diurnal and nocturnal insect collections concluded insignificant. Outside the exclosure 574 total insects were collected with 291 insects captured inside. Inside the exclosures contain higher diversity with a Shannon index of 2.85 with a 0.07 difference outside the exclosure at 2.78. The location diversity indices proved inside the exclosure being more diverse while having lower population and lesser families present. No discernable patterns were observed during the 6-week period due to family level being too coarse to detect differences, abundance of vegetation, and short time to observe effect. Results suggest ungulate herbivore activity does not result in detrimental effects on the insect diversity in Texas Hill Country. Data may represent skewed results from short exclosure presence of one year. The difference inside and outside exclosures is likely to increase with time later presenting more accurately ungulate herbivore effects on the insect community.