Choosing sampling methods for Chilopoda, Diplopoda and Isopoda (Oniscidea): a case study for ferruginous landscapes in Brazilian Amazonia

Abstract

The edaphic fauna plays an important role in the organic matter dynamics of the soil. Millipeds (Diplopoda),centipeds (Chilopoda) and isopods (Isopoda) are among the main components of the soil fauna. Vegetationstructure represents one of the main factors influencing composition and diversity of these species that inhabitleaf litter and soil, what is particularly important in the Amazon Forest, where there are several singular ve-getation types. Savannah and forest areas stand out in ferruginous hills, which represents one of the most poorlyknown and highly threatened ecosystems in the Amazon. However, sampling the edaphic fauna in high diversitysites represents a challenging task. Studies have shown that sampling method may influence observed patterns ofdiversity. From this perspective, the present study aimed to (i) investigate whether assemblages of Chilopoda,Diplopoda and Isopoda differ between vegetation types in the Amazon, (ii) indicate how biological parametersbehave in such communities, (iii) identify which method or combination of methods is better suited to samplespecies richness and (iv) quantify the efficiency of each method regarding time of work and cost. Sampling wasconducted by means of hand collection, leaf litter collection, hay-bait traps and soil sampling in four patches,two in the savannah (also called canga) and two in the forest. Richness was higher in forest habitats forChilopoda and Diplopoda, while for Isopoda there was no significant difference. Species composition also dif-fered between vegetation types for Chilopoda and Isopoda, but not for Diplopoda. Beta diversity between ve-getation types was mainly determined by nestedness and balancing, while turnover was the main beta diversitycomponent responsible for differences among methods. Soil sampling and hand collection added more species tothe samples, therefore, this combination was the most efficient to access diversity. Our results support thehypothesis that differences in the soil cover promoted by distinct vegetation types influence the species diversityand composition of edaphic fauna. The differences were mainly determined by nestedness and balancing, in-dicating that the fauna sampled in the canga represents a subset of those present in the surrounding forest. In thissense, even in ecosystems with distinct vegetation types, the combination of soil and surface sampling methods isrecommended. Lastly, the present study proposes a set of decision rules and a key to select the most appropriatemethod to sample the studied taxonomic groups