Abstract Detail

Ecology/Pathology

Walker, Donald M. [1], Lawrence, Brandy R. [2], Graham, Sean P. [1], Wooten, Jessica [1].

A metagenomics approach to the top-down effect; red-backed salamander effects on fungal communities in Midwestern upland deciduous forests.

A classic ecological study by Paine (1974) demonstrated that removal of a top predator from tidal pools results in changes in community structure. Since this landmark study, the structure within diverse food webs has been shown to be influenced by both top-down and bottom-up effects. The flow of energy from biomass in detrital food webs can affect both lower (bottom-up) and higher (top-down) trophic levels. Saprophytic bacteria and fungi play a dominant role in determining energy flow among and within trophic levels, especially in deciduous forests where nutrient and biomass inputs from the canopy support an inverted food web. In the eastern United States, the apex of this food chain is occupied by a diverse and abundant assemblage of salamanders. This study explores the top-down effect of Plethodon cinereus on the fungal community composition in a Midwestern deciduous forest using 454 pyrosequencing to determine if fungal community structure changes with respect to the absence/presence of red-backed salamanders. During the fall of 2013, eight-0.5m² metal fleshing enclosures were erected around the natural territorial range of one red-backed salamander. Organic matter containing decaying leaves, wood, and top 2-3 cm of soil was collected from the center of each enclosure at three different times over a 42 day period (n = 24). Samples were collected on day 1 when each enclosure contained one salamander. After three weeks (day 21) four salamanders were evicted from each of four enclosures and a second sample was collected. The last sample was taken on day 42. Total DNA was isolated from each sample and the ITS region of rDNA and partial ribosomal large subunit was amplified and sequenced using 454 pyrosequencing. Results indicate that upon salamander eviction (day 21), invertebrate communities are no longer under the pressure of salamander predation; this allows them to thrive, increasing mycoherbivory on fungal communities, thus altering fungal species composition in absence when compared to presence plots. Statistically significant shifts in fungal communities were documented in the presence but not absence of P. cinereus (day 21 vs. day 42). We hypothesize that any available seasonally fluctuating niches are quickly colonized by resident fungal species when a keystone predator is removed from an ecosystem thus demonstrating a top-down effect.

1 - The University of Findlay, Department of Natural Sciences, 1000 N Main St, Findlay, OH, 45840, USA
2 - The University of Findlay, Pharmacy, 1000 N Main St, Findlay, OH, 45840, USA

Keywords:
454 pyrosequencing
Plethodon cinereus
Metagenomics.

Presentation Type: Offered Paper - Paper
Session: 1
Location: Room 103 AB/Kellogg Hotel and Conference Center
Date: Monday, June 9th, 2014
Time: 8:30 AM
Number: 1001
Abstract ID:71
Candidate for Awards:None