Biology subjects

Penn, H. J.

Publications and source records attributed to Penn, H. J..

4 recordsLinked to original sources

bioRxiv2024

Red harvester ants (Pogonomyrmex barbatus) do not distinguish between sorghum head mold symptomatic and asymptomatic seeds

Red harvester ants, Pogonomyrmex barbatus (Smith) (Hymenoptera: Formicidae), common in the Lower Rio Grande Valley of Texas, are known to gather seeds from areas around their nests and store the seeds inside their nests for later consumption. As these ants often nest in and near agricultural fields, some of these seeds may be from crops and may also be infected with fungal plant pathogens. These pathogens can degrade seed coats and may cause the seeds to rot within the ant nests, decreasing storage time and potentially spreading the pathogen to other stored seeds. We studied how head mold, a common sorghum disease, changed ant preferences for sorghum seeds. Using seed depots, we evaluated foraging preferences for sorghum seeds with and without head mold and then monitored how many seeds of each type were collected by the colonies after 1, 2, 4, and 24 hours. We found that red harvester ants did not have any significant preference for infected or uninfected seeds, taking both equally over time. Given this non-preference, ants were assumed to be storing infected seeds next to uninfected seeds within their colonies. However, the risk that stored pathogen-infected seeds poses as a source of future seed infection to seeds within the nest and plants in the surrounding field needs to be further examined.

ecology↗

bioRxiv2024

Red harvester ant nests impact soil compaction but not temperature in peri-urban habitats of the Lower Rio Grande Valley

Ants are vital ecosystem engineers that can influence soil properties, subsequent soil processes, and associated biota via underground nest construction. Harvester ants consume seeds and are often found in arid areas, frequently altering soil chemistry and bulk density of the soils in and around their nest sites. Many species of harvester ants also intentionally remove vegetation around nest openings, creating cones or discs of bare soil that may further alter soil temperatures. However, much of the work investigating the impacts of harvester ants on soil properties has occurred in shrubland and grassland settings rather than suburban environments. We aimed to determine if Pogonomyrmex barbatus (Smith) (Hymenoptera: Formicidae) nests in a suburban habitat in the Lower Rio Grande Valley in Texas similarly altered soil properties. First, we measured active nest disc size to determine changes and colony persistence. Then we assessed soil compaction and surface temperature along a gradient centered on the disc. We found that disc size did not increase throughout the two-year observation period and that nests with smaller discs were less likely to persist between years. While we did not observe any changes in surface temperature across the gradient, we found a significant increase in soil compaction with greater distance from the center of the disc. These data indicate that increased nest size increases the extent of soil impacted. The impacts of nests reducing soil compaction, particularly within a suburban landscape with precipitation run-off issues and a highly disturbed plant community should be addressed in future studies.

ecology↗

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↗