Methodological considerations for monitoring soil/litter arthropods in tropical rainforests using DNA metabarcoding, with a special emphasis on ants, springtails and termites

Yves Basset,Kate H J Perez,Luis F De León,José Alejandro Ramirez,Filonila Perez,Michael T G Wright,Yacksecari Lopez,Greg P A Lamarre,Marleny Rivera,José G Palacios-Vargas,Gabriela Castaño-Meneses,Mehrdad Hajibabaei,David A Donoso,Ricardo Bobadilla,Héctor Barrios

doi:10.3897/mbmg.4.58572

Abstract

Robust data to refute or support claims of global insect decline are currently lacking, particularly for the soil fauna in the tropics. DNA metabarcoding represents a powerful approach for rigorous spatial and temporal monitoring of the taxonomically challenging soil fauna. Here, we provide a detailed field protocol, which was successfully applied in Barro Colorado Island (BCI) in Panama, to collect soil samples and arthropods in a tropical rainforest, to be later processed with metabarcoding. We also estimate the proportion of soil/litter ant, springtail and termite species from the local fauna that can be detected by metabarcoding samples obtained either from Berlese-Tullgren (soil samples), Malaise or light traps. Each collecting method detected a rather distinct fauna. Soil and Malaise trap samples detected 213 species (73%) of all target species. Malaise trap samples detected many ant species, whereas soil samples were more efficient at detecting springtail and termite species. With respect to long-term monitoring of soil-dwelling and common species (more amenable to statistical trends), the best combination of two methods were soil and light trap samples, detecting 94% of the total of common species. A protocol including 100 soil, 40 Malaise and 80 light trap samples annually processed by metabarcoding would allow the long-term monitoring of at least 11%, 18% and 16% of species of soil/litter ants, springtails and termites, respectively, present on BCI, and a high proportion of the total abundance (up to 80% of all individuals) represented by these taxa.

Highlights

Arthropods represent the majority of macroscopic terrestrial animal life, both in terms of species richness (Stork 2018) and biomass (Pimentel and Andow 1984), in the tropics (Basset et al 2012)
A nearly equal number of species was detected in Malaise trap and soil samples, whereas only half of that number was detected in light trap samples (Table 1)
A high number of springtail species were detected in soil samples, followed by Malaise samples, but very few species were detected in light trap samples (Fig. 1b)

Summary

Introduction

Arthropods represent the majority of macroscopic terrestrial animal life, both in terms of species richness (Stork 2018) and biomass (Pimentel and Andow 1984), in the tropics (Basset et al 2012) They provide critical services, including ecosystem functioning and human food security. Recent reports suggest catastrophic declines in current insect abundance, with potentially serious implications for ecosystem functioning This includes declines in the richness of insect species in temperate countries (Sánchez-Bayo and Wyckhuys 2019), insect biomass in Germany and Puerto Rico (Hallmann et al 2017; Lister and Garcia 2018), butterflies and moths in the United Kingdom (McDermott Long et al 2017), or insect pollinators worldwide (Goulson et al 2015). What is clear is that we currently lack robust data to refute or support claims of global insect decline, in the tropics (Basset and Lamarre 2019; Crossley et al 2020; van Klink et al 2020; Wagner 2020), not to mention scenarios of how insect populations will be affected by anthropogenic changes in the future (Lamarre et al 2020)

Methods

Results

Discussion

Conclusion