Quantitative Estimation of Epiphytic Invertebrate Populations

Abstract

Quantitative comparisons were made of the relative accuracy, precision, and cost of various population estimation techniques for epiphytic invertebrates. Quadrat clipping was often more accurate than the Gerking, Macan, Minto, or KUG samplers, yielding population estimates an average of sevenfold greater where differences were found. All quadrat sizes (112 cm2 to 1 m2) usually yielded equal estimates of epiphytic invertebrate populations. The spatial variance of replicate epiphytic invertebrate samples increased with population density and decreased with the size of sampler employed (R2 = 0.94; n = 497). All samplers yielded equivalent levels of sampling precision. A method providing provisional estimates of the requisite number of replicate samples for a given level of precision is presented. Greater replication is required at low invertebrate population density or when small samplers are used. The most cost effective sampler size for the phytofauna is about 500 cm2. Improved sampling design can result in up to fivefold reductions in sampling effort. Taxa examined include Acari, Amphipoda, Chironomidae, Cladocera, Copepoda, Gastropoda, Hirudinea, Lepidoptera, Nematoda, Oligochaeta, Ostracoda, Trichoptera, and Turbellaria.