Penn, H. J. | Search bioRxiv

bioRxiv2022

Differential patterns of taxonomic and functional diversity for two groups of canopy arthropods across spatial scales

AimArthropod diversity is often linked to variation in resource use, dispersal ability, habitat connectivity, and climate factors that differ across spatial scales. The aim of this research was to examine how species richness, functional diversity, and community composition of two taxa differing in functional roles and dispersal ability are structured across spatial scales and to identify the importance of vegetation, climate, and landscape in explaining these patterns at different scales. Location96 trees in 24 stands of 6 deciduous forest sites in 2 ecoregions of the eastern USA (North-Central Till Plain and Western Allegheny Plateau) Time period2000 Major taxa studiedCanopy dwelling ants (Hymenoptera: Formicidae) and spiders (Araneae) MethodsOrganisms were collected from tree canopies using insecticidal fogging. Ant and spider taxonomic and functional beta diversity were partitioned across four hierarchical spatial scales (individual tree, forest stand, site, and ecoregion). The contribution of climactic, landscape, and vegetation variables was determined using model selection. ResultsAnt and spider species richness, functional diversity, and community composition differed between taxa and across spatial scales. Alpha diversity (within trees) was lower than expected for both taxa and types of diversity, with host tree species supporting different species of ants and spiders. While beta components of species diversity among trees and forest stands was greater than expected for both taxa, spiders also showed significant levels of beta diversity among sites. Functional beta diversity was less scale-dependent than taxonomic beta diversity. Stand-level patterns of beta diversity were significantly predicted by variation in climate and landscape connectivity. Main conclusionsEffects of climate and landscape fragmentation on the diversity and community structure of both taxa indicate that anthropogenic climate change and land use change will alter canopy arthropod communities. Results also suggest that patterns of diversity among fragmentation metrics is influenced by differences in dispersal ability.

ecology↗

bioRxiv2022

Red harvester ant (Order: Hymenoptera) preference for cover crop seeds in South Texas

Harvester ants are known to selectively forage seeds, potentially impacting nearby plant community composition. In agricultural areas, harvester ants may be viewed as pests by foraging on crop seeds or as beneficials by preferentially removing weed seeds. However, little work has been done on harvester ant preferences for cover crop seeds. Local observations suggest that ants may take cover crop seeds, but no studies have evaluated ant agricultural impacts or seed preferences in the Lower Rio Grande Valley (LRGV). We examined red harvester ant (Pogonomyrmex barbatus Smith) preferences for commonly used cover crop seeds in the LRGV (vetch, oat, fescue, sunn hemp, and radish with wheatgrass as a control) and a commonly used bacterial seed inoculation treatment meant to increase root nodulation. We tested seed sets using choice tests housed in seed depots located within the foraging range of ant colonies with no prior exposure to the selected seeds. Of the evaluated cover crop seeds, wheatgrass and oat were the first to be removed entirely from the depot, with vetch remaining after 24 h. When we inoculated the two most preferred seeds to determine if there was a preference for non-inoculated seeds, we found no difference between inoculated and non-inoculated seeds. There were also significant changes in activity over time for both trials. These data indicate that harvester ant foraging preferences and activity can inform grower management recommendations regarding the risks of using certain cover crops and months sowing should be conducted in fields with known harvester ant presence.

ecology↗