Humans commonly apply chemicals to manage agroecosystems. If those chemicals influence the behaviour or survival of non-target arthropods, the food web could be altered in unintended ways. Glyphosate-based herbicides are among the most ubiquitous pesticides used around the world, yet little is known about if and how they might affect the success of terrestrial predatory arthropods in agroecosystems. In this study, we quantified the effects of a commercial formulation of a glyphosate-based herbicide on the activity of three predatory arthropod species that inhabit agricultural fields in the eastern United States. We also measured the survival of the most common species. We tested the reactions of the wolf spider, Pardosa milvina, to either direct application (topical) or contact with a treated substrate (residual). We quantified the reactions of a larger wolf spider, Hogna helluo, and a ground beetle, Scarites quadriceps, to a compound (topical plus residual) exposure. Pardosa milvina reduced locomotion time and distance under topical herbicide exposure, but increased speed and non-locomotory activity time on exposed substrate. Both H. helluo and S. quadriceps increased non-locomotory activity time under compound herbicide exposure. Over a period of 60 days post-exposure, residually exposed P. milvina exhibited lower survivorship compared to topically exposed and control groups. Thus, exposure of terrestrial arthropods to glyphosate-based herbicides affects their behaviour and long-term survival. These results suggest that herbicides can affect arthropod community dynamics separate from their impact on the plant community and may influence biological control in agroecosystems.

We present the first genome-wide molecular phylogeny of jumping spiders (Araneae: Salticidae), inferred from Anchored Hybrid Enrichment (AHE) sequence data. From 12 outgroups plus 34 salticid taxa representing all but one subfamily and most major groups recognized in previous work, we obtained 447 loci totalling 96,946 aligned nucleotide sites. Our analyses using concatenated likelihood, parsimony, and coalescent methods (ASTRAL and SVDQuartets) strongly confirm most previous results, resolving as monophyletic the Spartaeinae, Salticinae (with the hisponines sister), Salticoida, Amycoida, Saltafresia, and Simonida. The agoriines, previously difficult to place beyond subfamily, are finally placed confidently within the saltafresians as relatives of the chrysillines and hasariines. Relationships among the baviines, astioids, marpissoids, and saltafresians remain uncertain, though our analyses tentatively conclude the first three form a clade together. Deep relationships, among the seven subfamilies, appear to be largely resolved, with spartaeines, lyssomanines, and asemoneines forming a clade. In most analyses, Onomastus (representing the onomastines) is strongly supported as sister to the hisponines plus salticines. Overall, the much-improved resolution of many deep relationships despite a relatively sparse taxon sample suggests AHE is a promising technique for salticid phylogenetics.

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Anthropogenic substances have the potential to affect animal behavior either because they present a novel stimulus or because they interfere with natural chemical communication pathways. Such shifts can alter the dynamic between predators and potential prey, which might affect population success as well as the strength of food web linkages. We examined the foraging of two wolf spiders, Tigrosa helluo and Pardosa milvina (Araneae, Lycosidae), that are abundant in agroecosystems where they are routinely exposed to herbicides. We tested the hypothesis that the presence of a commercial formulation of a glyphosate-based herbicide would affect the prey capture behavior of these two wolf spiders. We tested the larger Tigrosa foraging on Pardosa or crickets (Acheta domesticus) and the smaller Pardosa foraging on crickets. Tigrosa subdued crickets more quickly and with fewer lunges than it took them to capture Pardosa. The presence of herbicide allowed Tigrosa to orient toward and capture both prey species more quickly but it did not affect the number of lunges required to subdue either prey. Herbicide did not affect the timing of prey capture for Pardosa but it did cause them to use more lunges in the process. Thus, herbicide had contrasting effects on foraging behavior of these two agrobiont predators, which means that it could shift the direction and strength of food web linkages in complex ways.

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