BUSCADOR RECOLECTA

Soil fauna play a key role in nutrient cycling and decomposition, and in recent years researchers have become more and more interested in this compartment of terrestrial ecosystems. In addition, soil fauna can act as ecosystem engineers by creating, modifying and maintaining the habitat for other organisms. Ecologists usually utilize alive catches in pitfalls traps as a standard method to study the activity of epigeic fauna in addition to relative abundance. Counts in pitfall traps can be used as estimates of relative activity to compare among experimental treatments. This requires taking independent estimates of abundance (e.g.: by sifting soil litter, mark-recapture), which can then be used as covariates in linear models to compare the levels of fauna activity (trap catches) among treatments. However, many studies show that the use of pitfall traps is not the most adequate method to estimate soil fauna relative abundances, and these concerns may be extensible to estimating activity. Here, we present two new types of traps devised to study activity in litter fauna, and which we call “cul-de-sac” and “basket traps” respectively. We experimentally show that, at least for litter dwellers, these new traps are more appropriate to estimate fauna activity than pitfall traps because: 1) Pitfall traps contain 3.5x more humidity than the surrounding environment, potentially attracting animals towards them when environmental conditions are relatively dry, 2) cul-de-sac and basket traps catch ca. 4x more both meso- and macrofauna than pitfall traps, suggesting that pitfall traps are underestimating activity; and 3) pitfall traps show a bias towards collecting 1.5x higher amounts of predators, which suggests that predation rates are higher within pitfall traps. We end with a protocol and recommendations for how to use these new traps in ecological experiments and surveys aiming at estimating soil arthropod activity., This work was funded by grants CGL2010-18602 and CGL2015-66192-R from the Spanish Ministerio de Economía y Competitividad (European funds FEDER), 020/2008 Spanish Organismo Autónomo de Parques Nacionales and P12-RNM-1521 from Junta de Andalucía (European funds FEDER), Peer reviewed

© The Author(s)., Soil fauna play a key role in nutrient cycling and decomposition, and in recent years, researchers have become more and more interested in this compartment of terrestrial ecosystems. In addition, soil fauna can act as ecosystem engineers by creating, modifying, and maintaining the habitat for other organisms. Ecologists usually utilize live catches in pitfalls traps as a standard method to study the activity of epigeic fauna in addition to relative abundance. Counts in pitfall traps can be used as estimates of relative activity to compare among experimental treatments. This requires taking independent estimates of abundance (e.g., by sifting soil litter, mark–recapture), which can then be used as covariates in linear models to compare the levels of fauna activity (trap catches) among treatments. However, many studies show that the use of pitfall traps is not the most adequate method to estimate soil fauna relative abundances, and these concerns may be extensible to estimating activity. Here, we present two new types of traps devised to study activity in litter fauna, and which we call “cul-de-sac” and “basket traps”, respectively. We experimentally show that, at least for litter dwellers, these new traps are more appropriate to estimate fauna activity than pitfall traps because: (1) pitfall traps contain 3.5× more moisture than the surrounding environment, potentially attracting animals towards them when environmental conditions are relatively dry; (2) cul-de-sac and basket traps catch ca. 4× more of both meso- and macrofauna than pitfall traps, suggesting that pitfall traps are underestimating activity; and (3) pitfall traps show a bias towards collecting 1.5× higher amounts of predators, which suggests that predation rates are higher within pitfall traps. We end with a protocol and recommendations for how to use these new traps in ecological experiments and surveys aiming at estimating soil arthropod activity, This work was funded by grants CGL2010-18602 and CGL2015-66192-R from the Spanish Ministerio de Economía y Competitividad (European funds FEDER), 020/2008 from Spanish Organismo Autónomo de Parques Nacionales, and P12-RNM-1521 from Junta de Andalucía (European funds FEDER) and the FPI fellowship (BES-2011-043505) to N.M.R. D. Ruiz-Lupión is enjoying a FPU (FPU13/04933) scholarship from the Spanish Ministerio de Educacion, Cultura y Deporte., Peer reviewed

This study has been funded by Spanish Ministry of Science and Innovation grants CGL2010-18602, CGL2015-66192-R and Andalusian grant P12-RNM-1521-EEZA to J.M.L., the European Regional Development Fund, Agencia Nacional de la Promoción de Ciencia y Tecnología (PICT 2016-1780), Argentina to A.T.A. and FPI fellowship (BES-2011-043505) to N.M.R, Dos tablas de datos: Animal abundance y Decomposition data, Peer reviewed

Litter decomposition in field experiment. A total of 280 mesocosms were settled under and away of 20 individuals of Z. lotus. The litter boxes thus contained either one single species of litter (20 litter boxes for each species and position treatment), 2-sp mixtures (20 litter boxes for each 2-species combination and position treatment) or 3-sp mixtures (20 litter boxes with the 3-species mixture and position treatment)., This study was supported by the Office of Secretary of Public Education of Mexico though the program Further Education Programme for Teachers (UNICACH-110). Further support was provided by the Spanish Research Agency (grant CGL2017-84515-R to FIP and grant CGL2015-66192-R to JML). We thank the Cabo de Gata-Níjar Nature Park for support during field work (permit: 2016-101-657)., Date Date of collection (1 - 07/13/2017, 2 - 01/13/2018, 3 -08/30/2018) Plant Plant (Ziziphus lotus fertility island) ID utmx Geographic Longitude for each plant utmy Geographic Latitude for each plant Box Mesocosm ID Island Location of the mesocosm (Away or Under shrub) Mixtures Litter plant diversity (species richness 1, 2, 3) Species Identity of the litter plant species with three levels: S. tenacissima, C. humilis and R. sphaerocarpa w_inic Litter initial dry mass (g) w_end Litter dry mass (g) after 184, 367 and 597 days in the field, Peer reviewed

The relative body size at which predators are willing to attack prey, a key trait for predator-prey interactions, is usually considered invariant. However, this ratio can vary widely among individuals or populations. Identifying the range and origin of such variation is key to understanding the strength and constraints on selection in both predators and prey. Still, these sources of variation remain largely unknown. We filled this gap by measuring the genetic, maternal and environmental variation of the maximum prey-to-predator size ratio (PPSRmax) in juveniles of the wolf spider Lycosa fasciiventris using a paternal half-sib split-brood design, in which each male was paired with two females and the offspring reared in two food environments: poor and rich. Each juvenile spider was then sequentially offered crickets of decreasing size and the maximum prey size killed was determined. We also measured body size and body condition of spiders upon emergence and just before the trial. We found low, but significant heritability (h2 = 0.069) and dominance and common environmental variance (d2 + 4c2 = 0.056). PPSRmax was also partially explained by body condition (during trial) but there was no effect of the rearing food environment. Finally, a maternal correlation between body size early in life and PPSRmax indicated that offspring born larger were less predisposed to feed on larger prey later in life. Therefore, PPSRmax, a central trait in ecosystems, can vary widely and this variation is due to different sources, with important consequences for changes in this trait in the short and long terms., This study was supported by a PhD grant (PD/BD/106059/2015) attributed to JFH by the Portuguese Science and Technology foundation (FCT), by the grant P12-RMN-1521 from the Andalusian government and by the grant CGL2015-66192-R from the Spanish Ministry of Economy and Competitiveness, both partially funded by the European Regional Development Found, both attributed to Jordi Moya-Laraño and to the FPU scholarship (FPU13/04933) from the Spanish Ministerio de Educacion, Cultura y Deporte to Dolores Ruiz-Lupión., Peer reviewed

Under ongoing climate change, the success of biological pest control might be at risk if in the process of massrearing, the populations of commercial biological control agents lose genetic variability in traits that allow adaptation linked to satisfactory pest control in future crop conditions. The isofemale line technique was used to estimate the broadsense heritability (H²) in 22 morphological, life history, physiological, and behavioral quantitative traits from two populations of the species Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae): one commercial, acquired from a company; and the other wild, obtained by the authors from field collections in the region where this species is native. None of the traits estimated in the commercial population held genetic variance (H²~0), whereas the H² of 5 traits related to development time and morphology were significant in the wild population. Analyzing together the isolines of both populations allowed increasing the number of significant H² estimates to 12, which included physiological traits such as desiccation and starvation resistance. Assuming similar genetic drift in both populations, the fact that heritability estimates in the commercial population were estimated to be almost null indicated that this population might have undergone selection leading to a decrease in genetic variability. Unintentional adaptations to long-term captive conditions can have drastic effects on the performance of BCAs. Low genetic variability in commercial populations may limit their within-generation persistence in the field, as well as their potential for between-generation rapid adaptation in response to environmental changes, ultimately jeopardizing pest control., This work was executed thanks to Grant CGL2015-66192-R funded by MCIN/AEl/10.13039/501100011033 and the “ERDF A way of making Europe”, Grant PID2019-103863RB-I00, funded by MCIN/AEl/10.13039/501100011033, Grant BES-2016-077723, funded by MCIN/AEI/ 10.13039/501100011033 and the “ESF Investing
in your future”, and Grant TED2021-129653B-I00, funded by MCIN/AEl/10.13039/501100011033 and the “European Union NextGenerationEU/PRTR”, Peer reviewed