PS 57-23 - Diversity and function of dung beetles in subtropical grasslands

Thursday, August 11, 2011
Exhibit Hall 3, Austin Convention Center
Christen H. Steele, MacArthur Agro-Ecology Research Center, Archbold Biological Station, Lake Placid, FL and Elizabeth Hermanson Boughton, MacArthur Agro-ecology Research Center, Archbold Biological Station, Lake Placid, FL


The suite of beneficial ecosystem services provided by dung beetles has been well documented in scientific literature; however, the quantity of service provided may be dependent upon dung beetle composition and functional group richness.  In managed ranchlands, dung beetle communities are altered by human disturbances including land use change, species introduction, and the use of parasiticides. It is not clearly understood how shifts in dung beetle composition and functional group richness may alter ecosystem services in an agricultural landscape. I propose to examine the richness, abundance and seasonal activity of dung beetle species on a cattle ranch in South Florida.  This study will characterize species composition in relation to habitat type, stocking density, fertilizer applications, and plant species composition. I hypothesize that species abundance and richness will be dominated by non-native introduced species (primarily the tunneler Onthophagus gazella). Dung baited pitfall traps will be used to collect beetles bi-weekly for one year. This survey will allow for detection of dung beetle functional groups (large tunnelers, small tunnelers, brooders, natives, and exotics) and their relative abundance. The functional groups will then be used to guide a mesocosm experiment to assess changes in ecosystem function (dung degradation) of experimentally altered dung beetle communities. I hypothesize that different combinations of beetles differentially affect the breakdown of dung and that functionally diverse combinations will break down dung at a faster rate than one species alone. 


A preliminary study conducted spring of 2010 was executed to gather data on species presence and determine the efficacy of various trapping methods. I found that live capture dung-baited pitfall traps are ineffective due to a high frequency of fire ant colonization. Dung beetle pitfall traps were found most effective when filled with a soap/water solution. Contrary to the original project hypothesis, species abundance data gathered from the preliminary sampling was dominated by the native tunneler Onthophagus hecate, comprising 55% of the beetles trapped. Non-native species accounted for 31% of trapped beetles and included the African species Onthophagus depressus and Onthophagus gazella.  Notably, beetles within the large native beetle functional group were not found while sampling. This functional group would include species such as Phaneous vindex and Canthon piluarius. The preliminary sampling demonstrates that non-native species play a significant role in community composition. Future work will investigate how pasture management affects dung beetle composition and examine how dung beetle functional diversity affects the ecosystem function of dung degradation.

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