BIOTROPICA 40(6): 728–735 2008 10.1111/j.1744-7429.2008.00425.x Cost-efficiency of Subsampling Protocols to Evaluate Oribatid-Mite Communities in an Amazonian Savanna Evanira M. R. Santos, Elizabeth Franklin 1 Instituto Nacional de Pesquisas da Amazˆ onia (INPA), Coordenac ¸˜ ao de Pesquisas em Entomologia, CP 478, 69011-970, Manaus, AM, Brasil and William E. Magnusson Instituto Nacional de Pesquisas da Amazˆ onia (INPA), Coordenac ¸˜ ao de Pesquisas em Ecologia, CP 478, 69011-970, Manaus, AM, Brasil ABSTRACT Sampling oribatid mites in large areas using conventional methods is expensive, time-consuming, and this constrains their use in environmental monitoring programs. We used samples collected in 38 plots of 3.75 ha spread over 30,000 ha in an Amazonian savanna to evaluate the reduction in costs and person-hours in sampling and sorting and to elaborate cost-effective protocols. Ten samples per plot were collected and extracted using a Berlese-Tullgren apparatus. In the laboratory, samples were reduced to 50, 25, 12.5, and 6.25 percent of the initial content. Field-effort reduction was estimated by reducing the number of subsamples per plot. Dissimilarity matrices were generated using Bray–Curtis, Sørensen, and Chao–Sørensen indices. Correlations between each reduced-effort dissimilarity matrix and 100 or 50 percent sorting were used as an index of how much information was retained in reduced-effort sampling, and could still be used in multivariate analyses. The effects of most predictor variables on mite composition were detected in data based on every level of sample reduction. The intensive sampling was insufficient to reveal the full oribatid-mite fauna in the savanna; as more plots were sampled, more species were recorded. Our data indicate subsampling protocols for biodiversity assessment of oribatid mites in savanna that increase field and laboratory efficiency, and optimize both taxonomic and ecological aspects of the investigation. Abstract in Portuguese is available at http://www.blackwell-synergy.com/loi/btp. Key words: biodiversity assessment; cost-efficient protocols; intensive sampling; inventory; litter arthropods; sampling effort; soil mites. THE ALTER DO CH˜ AO PROJECT (Pilot Program to Conserve the Brazilian Rain Forest, PPD-G7) developed in Alter do Ch˜ ao, Par´ a State, Brazil was a precursor to the development of the RAPELD system (Magnusson et al. 2005) used in the Brazilian Government Program for Biodiversity Research (PPBio) designed to evaluate biodiversity throughout Brazil. One of the difficulties in the de- sign and implementation of monitoring programs is that the costs are often too high and therefore the program is unlikely to con- tinue for more than a few years (Danielsen et al. 2003). For long- term monitoring programs, the sampling protocol should cover sufficient area and encompass seasonal variation (Sørensen et al. 2002), and the most appropriate and cost-effective sampling and sorting techniques should be identified for the area or taxa in question. Predatory soil mites and mites of the Suborder Oribatida can be used in soil ecological classification and assessment (Ruf & Beck 2005). Oribatid mites are associated with organic matter in most terrestrial ecosystems (Behan-Pelletier et al. 1999). In spite of being generalists, able to feed on a wide variety of resources, the feeding bi- ology of many species forms a gradient of phytophagous/fungivores, primary decomposers, secondary decomposers, predators, carni- vores, scavengers, and omnivores (Schneider et al. 2004a, b). In most Amazonian ecosystems, they have been sampled in all sea- sons, with the highest abundance and diversity in the top 3.5 cm (Franklin et al. 1997, 2001, 2005; Franklin & Morais 2006). Received 4 April 2007; revision accepted 24 March 2008. 1 Corresponding author; e-mail: beth@inpa.gov.br Kempson and Berlese-Tullgren apparatuses have been used to extract the soil mesofauna from soil and litter samples in Cen- tral Amazonia, the Berlese-Tullgren apparatus being the most com- monly used (Franklin & Morais 2006). Despite the lower efficiency compared to other sampling methods used for soil microarthropods (Andr´ e et al. 2002), the Berlese-Tullgren is cheaper and simpler to build, can be easily moved to the place of sampling, and can be ad- justed for large amount of samples (Franklin & Morais 2006), even in remote regions. Because of these advantages, and considering the wide geographical area of the project, the entomology team of the Alter do Ch˜ ao Project extracted the invertebrates from the litter and soil profile using a Berlese-Tullgren apparatus. This apparatus is not selective of any particular group and will extract a huge number of specimens, mainly belonging to the hyperdiverse group of oribatid mites. The proportion of morphospecies that cannot be assigned to named species and the number of scientist-hours required to process samples increase dramatically for smaller-bodied taxa, especially in tropical forests (Lawton et al. 1998); a habitat difficult to work in and where considerable innovation is required to sample the biota (Stork & Gaston 1990). In the Alter do Ch˜ ao project, the long period necessary for identification meant that the oribatid mites could not be included in the initial analyses with soil properties, vascular plants, birds, reptiles, amphibians, and ants. Sampling soil mesofauna has been criticized as being time- consuming and expensive in terms of sampling effort in the field, and laboratory. Several strategies have been proposed to reduce time and expense for hyperdiverse groups, such as the identification of 728 C  2008 The Author(s) Journal compilation C  2008 by The Association for Tropical Biology and Conservation THE฀JOURNAL฀OF฀TROPICAL฀BIOLOGY฀AND฀CONSERVATION