Effectiveness of sampling methods and further sampling for accessing spider diversity: a case study in a Brazilian Atlantic rainforest fragment

Abstract

The current biodiversity crisis makes the quantification of the diversity and the description of organism distribution particularly pressing. Biological inventories are among the most effective ways to improve the knowledge about local biota, but they can be very time and money‐consuming. The determination of adequate sampling effort and the selection of cost‐effective collecting methods are critical issues. In this article, a spider diversity inventory in an Atlantic semi‐deciduous forest fragment in Brazil was used to compare the efficiency of three collecting methods in two different seasons in order to propose an optimised sampling protocol. The worthiness of increasing sampling effort in the target area and similar tropical ecosystems was estimated and evaluated in terms of its cost‐effectiveness. For a better sampling of the spider community, it is suggested that a proportion of 55, 29 and 16% of total sampling hours should be dedicated to nocturnal hand collecting (NHC), pitfall traps and beating trays, respectively, in the rainy season. If only one method can be applied, the most efficient in terms of species per sampling is the NHC. A completeness of 70% of the estimated spider species richness (as predicted by the Chao1 estimator) was observed in the complete inventory and increasing sampling effort in the studied area may be highly ineffective when the costs involved are considered. Other studies in similar tropical rainforest areas also presented completeness around 70%, which might be a threshold from which the sampling effort necessary to raise the observed species richness substantially starts to be ineffective.

Optimizing survey methods for spiders and harvestmen assemblages in an Amazonian upland forest

“…Differently, the beating tray method collected more spider species and more individuals than either the nocturnal search or Winkler methods. In that regard, our findings differ from other studies (Coddington et al, 1991;Cardoso, 2008;Azevedo et al, 2014) and cast doubt on the claim that nocturnal search is the most productive method for accessing spider richness and should be used alone in tropical forests (Azevedo et al, 2014). Based on our results, the performances of the beating tray and nocturnal search approaches are equivalent for describing the local richness of spiders in the Urucu basin and both methods should be used simultaneously to describe it in the Amazon basin.…”

“…Multiple methods and several replicates are used to sample spiders in many studies and the accumulation curves are also still not asymptotic (Coddington et al, 1991;Bonaldo et al, 2009;Cabra-García et al, 2010;Azevedo et al, 2014). Therefore, a traditional spider sampling protocol is usually not the most efficient strategy for studies of assemblage associations with environmental variables and ecological impact.…”

“…Although sampling method performance may vary among different taxonomic groups (see Gardner et al, 2008), in tropical forests many different taxonomic groups have been usually sampled together, using a combination of selected sampling methods (e.g., Bonaldo et al, 2009) and requiring massive sampling effort. Given a sufficiently high sample effort, the combination of several sampling methods should adequately represent both species richness and composition (Azevedo et al, 2014). However, the use of several sampling methods is not necessarily optimal for improving monitoring and evaluation programs (Gardner et al, 2008;Porto et al, 2016).…”

Gauging megadiversity with optimized and standardized sampling protocols: A case for tropical forest spiders

“…Fourth, collecting should be conducted when vegetation is dry, when most collecting methods are more efficient. Although collecting in the rainy season may yield more species than in the dry season (Azevedo et al, 2014), it may be more time-consuming and therefore eventually become more expensive-in our field test, two to three collectors needed 4-5 days to collect 24 hand-collected samples because of intermittent rain during the light rainy season. A possible compromise and our recommendation for maximum efficiency is to collect shortly after the rainy season.…”

Climatic Conditions Drive the Abundance and Diversity of Spiders Community in an Atlantic Forest Fragment

“…According to Dias et al (2006) the influence of temperature and rainfall variation in spiders communities change according to the vegetation type and geographical region. For instance, in areas with markedly rainfall seasonality, higher abundance and species richness were found during the rainy season (Azevedo et al 2014). Seasonal patterns for spider assemblages may vary even in different regions of the same state but that are composed of different environments (Rodrigues et al 2016), indicating that each biome has species specifically adapted to survive under the climatic and environmental constraints of the habitat in which they occur.…”