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1. Red Imported Fire Ants Reduce Invertebrate Abundance, Richness, and Diversity in Gopher Tortoise Burrows

   https://doi.org/10.3390/d13010007  

   Epperson, Deborah M.; Allen, Craig R.; Hogan, Katharine F. (January 2021, Diversity)

   null (Ed.)

   Gopher Tortoise (Gopherus polyphemus) burrows support diverse commensal invertebrate communities that may be of special conservation interest. We investigated the impact of red imported fire ants (Solenopsis invicta) on the invertebrate burrow community at 10 study sites in southern Mississippi, sampling burrows (1998–2000) before and after bait treatments to reduce fire ant populations. We sampled invertebrates using an ant bait attractant for ants and burrow vacuums for the broader invertebrate community and calculated fire ant abundance, invertebrate abundance, species richness, and species diversity. Fire ant abundance in gopher tortoise burrows was reduced by >98% in treated sites. There was a positive treatment effect on invertebrate abundance, diversity, and species richness from burrow vacuum sampling which was not observed in ant sampling from burrow baits. Management of fire ants around burrows may benefit both threatened gopher tortoises by reducing potential fire ant predation on hatchlings, as well as the diverse burrow invertebrate community. Fire-ant management may also benefit other species utilizing tortoise burrows, such as the endangered Dusky Gopher Frog and Schaus swallowtail butterfly. This has implications for more effective biodiversity conservation via targeted control of the invasive fire ant at gopher tortoise burrows. 

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2. Biochemical variability in sponges across the Caribbean basin

   https://doi.org/10.1111/ivb.12341  

   Clayshulte Abraham, Amelia; Gochfeld, Deborah J.; Macartney, Keir; Mellor, Amelia; Lesser, Michael P.; Slattery, Marc (July 2021, Invertebrate Biology)

   Abstract Sponges are a diverse phylum of sessile filter‐feeding invertebrates that are abundant on Caribbean reefs and provide essential ecological services, including nutrient cycling, reef stabilization, habitat, and food for a variety of fishes and invertebrates. As prominent members of the benthic community, and thus potential food resources, factors determining the biochemical and energetic content of sponges will affect their trophic contributions to coral reef ecosystems. In order to evaluate the influence of geographic variation on biochemical composition and energetic content in the tissue of sponges, we collected several common and widespread species (Agelas conifera,Agelas tubulata,Amphimedon compressa,Aplysina cauliformis,Niphates amorpha,Niphates erecta, andXestospongia muta) from multiple shallow reefs in four countries across the Caribbean Basin, including Belize, Curaçao, Grand Cayman, and St. Croix, U.S. Virgin Islands. In addition, we correlated inherent species‐level traits, including the production of antipredator chemical defenses and the relative abundance of microbial symbionts, with biochemical and energetic content. We found that energetic content was higher in sponges with antipredator chemical defenses, and was significantly correlated with the concentration of chemical extracts from these sponges. We also noted that sponges with high microbial abundance contained significantly more soluble protein than sponges with low microbial abundance. Finally, both biochemical and energetic content varied significantly among sponges from different locations; sponges from Grand Cayman had the highest lipid and energetic content, whereas sponges from Belize had the highest carbohydrate content but lowest energetic content. Despite similar environmental conditions at these sites, our results demonstrate that biochemical and energetic content of sponges exhibits geographic variability, with potential implications for the trophic ecology of sponges throughout the Caribbean Basin. 

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3. Functional redundancy buffers mobile invertebrates against the loss of foundation species on rocky shores

   https://doi.org/10.3354/meps13795  

   Elsberry, LA; Bracken, MES (September 2021, Marine Ecology Progress Series)

   Foundation species are vital to the maintenance of biodiversity and ecosystem functioning in many systems. On rocky shores, rockweeds (large brown algae in the Order Fucales) have the potential to provide habitat and ameliorate stress for mobile invertebrates. To determine the relative role of 2 rockweeds ( Silvetia compressa and Pelvetiopsis spp.) as foundation species at sites along a latitudinal gradient, we conducted observational surveys and then initiated a 12 mo removal experiment. We found that richness and abundance of mobile invertebrates declined over time when rockweeds were removed, but only at the southernmost site. In contrast, at our other sites, there was no change in the richness and abundance of mobile invertebrates following rockweed removal. At the southern site, rockweeds played an important role in maintaining mobile invertebrate diversity. At our central and northern sites, rockweeds were less important in maintaining the diversity of mobile invertebrates. At these sites, alternative species, including bladed and branching taxa in the genera Mastocarpus , Mazzaella , Corallina , and Endocladia , co-occur with rockweeds and can buffer the system against their loss. However, these alternative foundation species are rare to absent at the southern site, potentially due to greater physical stress. The loss of rockweed foundation species, which are declining at our southern site, can have cascading effects by causing local co-extinctions of associated species. This study highlights the importance of foundation species, especially in areas where their functional redundancy is low, and how the loss of foundation species can alter diversity, leading to potential changes in ecosystem functioning. 

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4. Nitrogen and phosphorus enrichment cause declines in invertebrate populations: a global meta‐analysis

   https://doi.org/10.1111/brv.12771  

   Nessel, Mark P.; Konnovitch, Theresa; Romero, Gustavo Q.; González, Angélica L. (June 2021, Biological Reviews)

   ABSTRACT Human‐driven changes in nitrogen (N) and phosphorus (P) inputs are modifying biogeochemical cycles and the trophic state of many habitats worldwide. These alterations are predicted to continue to increase, with the potential for a wide range of impacts on invertebrates, key players in ecosystem‐level processes. Here, we present a meta‐analysis of 1679 cases from 207 studies reporting the effects of N, P, and combined N + P enrichment on the abundance, biomass, and richness of aquatic and terrestrial invertebrates. Nitrogen and phosphorus additions decreased invertebrate abundance in terrestrial and aquatic ecosystems, with stronger impacts under combined N + P additions. Likewise, N and N + P additions had stronger negative impacts on the abundance of tropical than temperate invertebrates. Overall, the effects of nutrient enrichment did not differ significantly among major invertebrate taxonomic groups, suggesting that changes in biogeochemical cycles are a pervasive threat to invertebrate populations across ecosystems. The effects of N and P additions differed significantly among invertebrate trophic groups but N + P addition had a consistent negative effect on invertebrates. Nutrient additions had weaker or inconclusive impacts on invertebrate biomass and richness, possibly due to the low number of case studies for these community responses. Our findings suggest that N and P enrichment affect invertebrate community structure mainly by decreasing invertebrate abundance, and these effects are dependent on the habitat and trophic identity of the invertebrates. These results highlight the important effects of human‐driven nutrient enrichment on ecological systems and suggest a potential driver for the global invertebrate decline documented in recent years. 

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5. Foundation species promote community stability by increasing diversity in a giant kelp forest

   https://doi.org/10.1002/ecy.2987  

   Lamy, Thomas; Koenigs, Craig; Holbrook, Sally J.; Miller, Robert J.; Stier, Adrian C.; Reed, Daniel C. (February 2020, Ecology)

   Abstract Foundation species structure communities, promote biodiversity, and stabilize ecosystem processes by creating locally stable environmental conditions. Despite their critical importance, the role of foundation species in stabilizing natural communities has seldom been quantified. In theory, the stability of a foundation species should promote community stability by enhancing species richness, altering the population fluctuations of individual species, or both. Here we tested the hypothesis that the stability of a marine foundation species, the giant kelpMacrocystis pyrifera, increased the stability of the aggregate biomass of a phylogenetically diverse assemblage of understory algae and sessile invertebrates that compete for space beneath the giant kelp canopy. To achieve this goal, we analyzed an 18‐yr time series of the biomass of giant kelp and its associated benthic community collected from 32 plots distributed among nine shallow reefs in the Santa Barbara Channel, USA. We showed that the stability of understory algae and sessile invertebrates was positively and indirectly related to the stability of giant kelp, which primarily resulted from giant kelp's direct positive association with species richness. The stability of all community types was positively related to species richness via increased species stability and species asynchrony. The stabilizing effects of richness were three to four times stronger when algae and invertebrates were considered separately rather than in combination. Our finding that diversity–stability relationships were stronger in communities consisting of species with similar resource requirements suggests that competition for shared resources rather than differential responses to environmental conditions played a more important role in stabilizing the community. Increasing threats to structure‐forming foundation species worldwide necessitates a detailed understanding of how they influence their associated community. This study is among the first to show that dampened temporal fluctuations in the biomass of a foundation species is an important determinant of the stability of the complex communities it supports. 

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