A microtiter plate procedure for evaluating fungal functional diversity

Abstract

A method (FungiLog) was developed that allows a quantitative approach to examining aspects of fungal functional diversity. The BIOLOG microtiter plate method for measuring bacterial functional diversity was modified for use with fungal assemblages. Each BIOLOG plate contains 95 different carbon substrates. Eight different tetrazolium dyes were evaluated and dimethylthiazolyl-diphenyltetrazolium bromide (MTT) was chosen as the most suitable indicator of fungal growth. Procedures for inoculum preparation from a variety of substrates and inoculation into modified BIOLOG SF-N microplates were devised. By also plating out inoculum used to inoculate the FungiLog plates, taxonomic data can be obtained in conjunction with functional diversity. The FungiLog method was subsequently evaluated for detecting landscape patterns of fungal functional diversity using decaying lechuguilla (Agave lechuguilla) leaves placed along an elevational gradient in Big Bend National Park, Texas, in 5 vegetation zones. Sites ranged from a high elevation (2098 m) zone dominated by live oak (Quercus emoryi) and pinyon pine (Pinus cembroides) to a low land Chihuahuan Desert scrub (973 m). Ten, preweighed, 10-cm pieces of lechuguilla leaves were collected from each vegetation zone, 5 per transect, after 6 mo decomposition. FungiLog data were used to calculate two measures of fungal functional diversity, substrate richness and total activity. FungiLog patterns distinguished differences in total activity and substrate richness among the low elevational and the high elevational sites at this stage in the decomposition of lechuguilla leaves. Furthermore, litter decomposition was greater for sites with high fungal functional diversity.