Assessing Fungal Community Structure from Mineral Surfaces in Kartchner Caverns Using Multiplexed 454 Pyrosequencing
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Research on the distribution and structure of fungal communities in caves is lacking. Kartchner Caverns is a wet and mineralogically diverse carbonate cave located in an escarpment of Mississippian Escabrosa limestone in the Whetstone Mountains, Arizona, USA. Fungal diversity from speleothem and rock wall surfaces was examined with 454 FLX Titanium sequencing technology using the Internal Transcribed Spacer 1 as a fungal barcode marker. Fungal diversity was estimated and compared between speleothem and rock wall surfaces, and its variation with distance from the natural entrance of the cave was quantified. Effects of environmental factors and nutrient concentrations in speleothem drip water at different sample sites on fungal diversity were also examined. Sequencing revealed 2,219 fungal operational taxonomic units (OTUs) at the 95 % similarity level. Speleothems supported a higher fungal richness and diversity than rock walls. However, community membership and the taxonomic distribution of fungal OTUs at the class level did not differ significantly between speleothems and rock walls. Both OTU richness and diversity decreased significantly with increasing distance from the natural cave entrance. Community membership and taxonomic distribution of fungal OTUs also differed significantly between the sampling sites closest to the entrance and those furthest away. There was no significant effect of temperature, CO2 concentration, or drip water nutrient concentration on fungal community structure on either speleothems or rock walls. Together, these results suggest that proximity to the natural entrance is a critical factor in determining fungal community structure on mineral surfaces in Kartchner Caverns.
KeywordsCave biology Speleology Community structure Cave microbiology Fungal ecology 454 sequencing
The authors would like to thank Arizona State Parks, the RIM volunteers, and the Kartchner Caverns Cave Unit for all of the support they have provided in sampling and teaching us about Kartchner. Special thanks goes to Steve Willsey for leading the sampling expeditions and Dr. Bob Casavant for organizing them. We would also like to thank Jana U’Ren for her help with the statistical analyses. Thanks are also due to Mary Kay Amistadi at ALEC for analyzing the drip water samples. This study was supported in part by the College of Agriculture and Life Sciences, University of Arizona, by the Arizona State Parks system, and by the National Science Foundation (NSF-MCB #0604300).
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