Recent research on invasive ants suggests that their success may be facilitated by increased resources at introduced locations stemming from the emergence of novel trophic interactions with abundant honeydew-producing Hemiptera. Moreover, those Hemiptera may themselves often be introduced or invasive. To test the importance of mutualisms for invasive species, we conducted a study in the southeastern United States of factors hypothesized to affect the abundance of an invasive ant native to South America, Solenopsis invicta. The study was conducted within grazing pastures, where S. invicta can be extremely abundant while also exhibiting substantial variability in abundance. A path analysis showed that the abundance of S. invicta was strongly and positively affected by the abundance of an invasive honeydew-producing mealybug native to Asia, Antonina graminis, and by the mealybugs' host grasses because of their strong positive effect on mealybug abundance. Abundance of the mealybug was primarily attributable to an invasive host grass native to Africa, Cynodon dactylon. The abundance of S. invicta was also positively affected by the abundance of other arthropods that they are likely to consume, and those arthropods were positively affected by the abundance of both the A. graminis host grasses and other plants. Thus the study shows that the distribution and abundance of different plant species could have important effects on the abundance of S. invicta through their effect on the ants' food resources. The results are also consistent with the hypothesis that the emergence of novel trophic interactions among invasive species can promote the abundance of invasive ants.
Physical modeling of buildings founded on layers of liquefiable sand has produced insightful data describing ground and building performance. A new publicly available NEEShub database, “FLIQ,” summarizes data from 9 large-scale centrifuge tests with 4 different lead experimentalists, various soil profiles, 49 stations of site and structure response, and more than 60 shaking events, that is, 405 events in total. Example correlations between ground-motion intensity measures and performance measures are presented to illustrate the usefulness of the database. The relationship between PGA at the surface and base is highly variable when liquefaction is observed; however, the relationship between the cumulative absolute velocity ( CAV) at the surface and base is relatively linear, even when liquefaction occurs. Additionally, the CAV was found to correlate well with settlement and can account for settlement history. Contrary to intuition, foundation settlement in liquefied soil is not directly correlated to bearing pressure; larger bearing pressures can decrease liquefaction occurrence and related settlements. The database has potential to grow through future community input.
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