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1. Transient effects of corridors on polygyne fire ants over a decade

   https://doi.org/10.1111/een.13214  

   Resasco, Julian ; Burt, Melissa A. ; Orrock, John L. ; Haddad, Nick M. ; Shoemaker, DeWayne ; Levey, Douglas J. ( December 2022 , Ecological Entomology)

   Although corridors are frequently regarded as a way to mitigate the negative effects of habitat fragmentation, concerns persist that corridors may facilitate the spread of invasive species to the detriment of native species.

   The invasive fire ant,Solenopsis invicta,has two social forms. The polygyne form has limited dispersal abilities relative to the monogyne form. Our previous work in a large‐scale corridor experiment showed that in landscapes dominated by the polygyne form, fire ant density was higher and native ant species richness was lower in habitat patches connected by corridors than in unconnected patches.

   We expected that these observed corridor effects would be transient, that is, that fire ant density and native ant species richness differences between connected and unconnected patches would diminish over time as fire ants eventually fully established within patches. We tested this prediction by resampling the three landscapes dominated by polygyne fire ants 6 to 11 years after our original study.

   Differences in fire ant density between connected and unconnected habitat patches in these landscapes decreased, as expected. Differences in native ant species richness were variable but lowest in the last 2 years of sampling.

   These findings support our prediction of transient corridor effects on this invasive ant and stress the importance of temporal dynamics in assessing population and community impacts of habitat connectivity.

    

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2. Predation shapes invertebrate diversity in tropical but not temperate seagrass communities

   https://doi.org/10.1111/1365-2656.13133  

   Freestone, Amy L. ; Carroll, Elizabeth W. ; Papacostas, Katherine J. ; Ruiz, Gregory M. ; Torchin, Mark E. ; Sewall, Brent J. ; Gómez‐Rodríguez, ed., Carola ( December 2019 , Journal of Animal Ecology)

   The hypothesis that biotic interactions are stronger at lower relative to higher latitudes has a rich history, drawing from ecological and evolutionary theory. While this hypothesis suggests that stronger interactions at lower latitudes may contribute to the maintenance of contemporary patterns of diversity, there remain few standardized biogeographic comparisons of community effects of species interactions.

   Using marine seagrasses as a focal ecosystem of conservation importance and sessile marine invertebrates as model prey, we tested the hypothesis that predation is stronger at lower latitudes and can shape contemporary patterns of prey diversity. To further advance understanding beyond prior studies, we also explored mechanisms that likely underlie a change in interaction outcomes with latitude.

   Multiple observational and experimental approaches were employed to test for effects of predators, and the mechanisms that may underlie these effects, in seagrass ecosystems of the western Atlantic Ocean spanning 30° of latitude from the temperate zone to the tropics.

   In predator exclusion experiments conducted in a temperate and a tropical region, predation decreased sessile invertebrate abundance, richness and diversity on both natural and standardized artificial seagrass at tropical but not temperate sites. Further, predation reduced invertebrate richness at both local and regional scales in the tropics. Additional experiments demonstrated that predation reduced invertebrate recruitment in the tropics but not the temperate zone. Finally, direct observations of predators showed higher but variable consumption rates on invertebrates at tropical relative to temperate latitudes.

   Together, these results demonstrate that strong predation in the tropics can have consequential impacts on prey communities through discrete effects on early life stages as well as longer‐term cumulative effects on community structure and diversity. Our detailed experiments also provide some of the first data linking large‐scale biogeographic patterns, community‐scale interaction outcomes and direct observation of predators in the temperate zone and tropics. Therefore, our results support the hypothesis that predation is stronger in the tropics, but also elucidate some of the causes and consequences of this variation in shaping contemporary patterns of diversity.

    

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3. Ground cover and native ant predation influence survival of metamorphic amphibians in a southeastern pine savanna undergoing restoration

   https://doi.org/10.1111/rec.13410  

   Burrow, Angela K. ; Crawford, Brian A. ; Maerz, John C. ( June 2021 , Restoration Ecology)

   Longleaf pine savannas historically supported abundant ground cover maintained by frequent fire but little other disturbance. Ground cover creates microclimates with lower temperatures, higher humidity, and increased soil moisture that may benefit wildlife, particularly small vertebrates such as amphibians. Today, most historical pine savannas have had extensive soil disturbance and altered fire regimes resulting in reduced ground cover and altered soil fauna communities including predatory invertebrates. We used a factorial terrestrial cage study to test the effects of native wiregrass (Aristidaspp.) cover and the exclusion of a native predatory ant (Dorymyrmex smithi) on the survival of post‐metamorphic Ornate chorus frogs (Pseudacris ornata) and Gopher frogs (Rana capito). Although we were unable to achieve full ant exclusion, ant reduction in exclusion treatments and plant cover had an interactive effect on metamorph survival. Ant exclusion tended to increase Gopher frog survival and this effect was more pronounced when wiregrass was present. Within ant treatments, survival of Gopher frogs increased slightly with increasing wiregrass cover. Ornate chorus frogs had a high probability of survival (>95%) in all ant exclusion treatments regardless of wiregrass cover; however, in treatments without ant exclusion, survival increased with increasing wiregrass cover. Our results demonstrate that high abundances of a native ant species and low coverage of native wiregrass, which are legacies of historical soil disturbance and altered fire regimes, interact to elevate mortality of juvenile amphibians. Minimizing soil disturbance and restoring native ground cover are likely important for amphibian habitat management within historical southeastern pine savannas.

    

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4. Management actions shape dung beetle community structure and functional traits in restored tallgrass prairie

   https://doi.org/10.1111/een.12950  

   Hosler, Sheryl C. ; Jones, Holly P. ; Nelson, Melissa ; Barber, Nicholas A. ( September 2020 , Ecological Entomology)

   1. Ecosystem restoration often focuses on re‐establishing species richness and diversity of native organisms. However, effective restoration requires re‐establishment of ecosystem functions and processes by all trophic levels. Functional trait descriptions of communities, including decomposer communities, may provide more comprehensive evaluations of restoration activities and management than taxonomic community metrics alone.

   2. We examined species and functional trait composition of dung beetle (Coleoptera: Scarabaeidae, Geotrupidae) communities across a 3–31 yearchronosequence of restored prairies, in which sites varied in the presence of re‐introduced bison and prescribed fire. We calculated functional diversity metrics and community‐weighted mean trait values using behavioural and morphological measurements. We also performed a dung decomposition experiment to measure an ecosystem function driven by these insects.

   3. Bison presence doubled beetle abundance and increased richness by 50%. Shannon diversity increased with restoration age, nearly doubling from the youngest to oldest restorations. Functional diversity was unchanged by site characteristics, except functional richness, which was reduced by bison and fire presence. Beetles were, on average, smaller in older restorations, although this pattern was weaker when bison were present.

   4. Dung decomposition was unaffected by site characteristics but increased with community weighted mean beetle mass. Dung decomposition was better predicted by mean trait values, suggesting that supporting large‐bodied species may be more important than species diversity in settings where maximizing decomposition function is a goal.

   5. Restoration managers should consider dung beetle communities and their functional characteristics when making management decisions, particularly where large grazers are a component of management strategies.

    

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5. Experimental warming weakens positive plant diversity effects on pitfall trap sampled ant diversity.

   Clark, A. ( April 2022 , Soil organisms)

   Abstract Ants are important components of many terrestrial ecosystems because of their high abundance, their central position in food webs, and because they can strongly influence ecosystem properties such as soil aeration, nutrient cycling, and plant community composition. Moreover, ants are also known to respond strongly to changes in environmental and biological conditions. In particular, two major anthropogenic environmental impacts – climate change and the loss of primary producers – may have interactive effects on ant communities. To examine this potential interaction, we quantified pitfall trap sampled ant diversity and activity across a fully factorial experiment manipulating temperature and grassland plant species richness at the Cedar Creek Ecosystem Science Reserve in Minnesota, USA. Consistent with previous arthropod studies, we found a significant increase in sampled ant diversity in plots with higher sown plant species richness, such that plots with the largest number of plant species also had the highest sampled ant diversity. However, the strength of this relationship declined significantly in experimentally warmed subplots, especially when considered for higher aggregated spatial scales of samples. Taken together, these results suggest that the positive effects of plant diversity on sampled ant diversity may be partially undermined under warmer conditions. 

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