Search

Benthic invertebrates play vital roles in estuarine ecosystems, but like other taxa they have been excluded from former marshlands by diking and land use conversion. Dike removal is one way of restoring marsh, but the response of benthic invertebrates has been little studied. Also understudied is variation in benthic invertebrate communities across entire deltas, particularly in the Pacific Northwest of North America where deltas receive high flows and sediment loads for their size. Our goals were to evaluate invertebrate response to large-scale dike removal on the Nisqually River Delta in Puget Sound, Washington, U.S.A., characterize delta-wide invertebrate community variation, and relate invertebrate response and spatial variation to environmental conditions. We sampled invertebrates annually from one year before to three years after dike removal in restoring marsh, previously restored marsh, undisturbed reference marsh, and adjacent tidal flats. Marine taxa immediately colonized the area recently restored to tidal inundation and population size grew exponentially thereafter for several of them. Community composition and diversity recovered completely, and density and biomass were approaching recovery three years later. Invertebrate communities converged between restoring and pre-existing marsh (previously restored and reference), suggesting an influence of reestablished connectivity. Just offshore from the dike line, invertebrates declined one year after dike removal but then rebounded indicating resilience to short-term disturbance. Dike removal effects were not detected farther offshore. Near the offshore edge of the delta, invertebrate biomass and body size were greater than elsewhere and a diverse assemblage of crustaceans, polychaetes, and bivalves was present. Farther inshore, tidal flats were dominated by a few species of small-bodied polychaetes and had higher density but lower biomass and diversity. Facultative detritivores, which can also filter feed, were the dominant feeding guild everywhere on the tidal flats. Density, biomass, diversity, and community composition on the marsh were more similar to the inner than outer tidal flats. Environmental variables most associated with invertebrate community variation were elevation, salinity, and sediment grain size and organic content. Our results are relevant to assessing performance and setting expectations for future restorations and have broad implications for the role of benthic invertebrates in estuarine ecosystems. [ABSTRACT FROM AUTHOR]

Nonnative species are a key agent of global change. However, nonnative invertebrates remain understudied at the community scales where they are most likely to drive local extirpations. We use the North American NEON pitfall trapping network to document the number of nonnative species from 51 invertebrate communities, testing four classes of drivers. We sequenced samples using the eDNA from the sample's storage ethanol. We used AICc informed regression to evaluate how native species richness, productivity, habitat, temperature, and human population density and vehicular traffic account for continent‐wide variation in the number of nonnative species in a local community. The percentage of nonnatives varied 3‐fold among habitat types and over 10‐fold (0%–14%) overall. We found evidence for two types of constraints on nonnative diversity. Consistent with Capacity rules (i.e., how the number of niches and individuals reflect the number of species an ecosystem can support) nonnatives increased with existing native species richness and ecosystem productivity. Consistent with Establishment Rules (i.e., how the dispersal rate of nonnative propagules and the number of open sites limits nonnative species richness) nonnatives increased with automobile traffic—a measure of human‐generated propagule pressure—and were twice as common in pastures than native grasslands. After accounting for drivers associated with a community's ability to support native species (native species richness and productivity), nonnatives are more common in communities that are regularly seasonally disturbed (pastures and, potentially deciduous forests) and those experiencing more vehicular traffic. These baseline values across the US North America will allow NEON's monitoring mission to document how anthropogenic change—from disturbance to propagule transport, from temperature to trends in local extinction—further shape biotic homogenization. [ABSTRACT FROM AUTHOR]

Beavers and their dams, once common in small streams throughout Eurasia and North America, are returning to their original range. Beaver dams are special habitats in the aquatic-terrestrial interface, but their macroinvertebrate fauna is hardly known. This study aims to qualify and quantify the invertebrate fauna of beaver dams, taking into account the maintenance status of the dams. Nine different areas covering the top, middle and base zones of eight maintained and eight abandoned beaver dams were sampled using a specially designed suction device. The invertebrate community of beaver dams proved to be diverse and predominantly rheophilic. Community composition reflects higher flow velocities in streamside habitats; this gradient is more pronounced in maintained than in abandoned dams. Shredders are the most abundant feeding type, but they are less frequent in streamside habitats, in particular in those of maintained dams, where passive filter feeders prevail. Terrestrial/Semiaquatic taxa colonising hygropetric areas were found in streamside habitats especially of abandoned dams. Our results underline that beaver dams provide a wide variety of environmental conditions and habitat types, which enhance biodiversity in small streams and their floodplains. Beaver dams in riverine landscapes should therefore be much more valued in floodplain conservation and management. [ABSTRACT FROM AUTHOR]

Biodiversity monitoring is imperative for understanding how changing climate may impact the distributions of taxa from single species to the spatial distribution of biological diversity. Large‐scale and cross‐taxa biodiversity monitoring also allows an empirical understanding of biogeographic patterns across taxa. One such pattern, where in taxonomic richness peaks at tropical latitudes are typically treated as a biogeographical rule with few notable exceptions. Here we leveraged the invertebrate pitfall collections of the National Ecological Observatory Network (NEON) across North America to describe patterns of local taxonomic richness across taxa and across taxonomic scale. We focused on Arthropoda, Annelida and Mollusca. Additionally, we estimated regional species richness using expert‐identified samples of three NEON sentinel taxa: Carabidae, Culicidae and Ixodida. To sample pitfall animals, we filtered storage ethanol and employed environmental DNA‐barcoding methodologies to amplify and sequence extracted DNA from the filtrate for two regions of a mitochondrial gene. We assigned taxonomic names to these sequences at 97% similarity to reference sequences and calculated local taxonomic richness at the levels of species, genus, family and order. We calculated local species richness for 12 common invertebrate taxa. We used generalized linear models to describe the relationships between taxonomic richness and spatial, climatic and abundance predictor variables. At four taxonomic scales, ranging from species to order, taxonomic richnessincreased significantly as a function of latitude. Of the twelve invertebrate taxa weexamined, seven mirrored this positive latitudinal gradient in species richness. At theregional scale, two of three NEON Sentinel Taxa showed positive latitudinal gradientsin species richness. Temperature, precipitation, abundance and sequence read numberplayed minor roles in explaining patterns of taxonomic richness. When considering these mostly temperate sites that span 46 degrees of latitude, we found no support for the expected negative latitudinal gradients across taxa and taxonomic scales. Instead, for many of these taxa and taxonomic scales, we observed significant, positive richness gradients with increasing latitude among ground‐dwelling invertebrate communities. Thus, one of the most 'general' patterns in biogeography was not found for most invertebrate taxa across temperate latitudes. [ABSTRACT FROM AUTHOR]

Wetland restoration often involves invasive‐plant suppression to encourage the recovery of native‐dominated vegetation communities. However, assessment of recovery is usually focused only on vegetation, and the response of other critical wetland biota, such as macroinvertebrates, is seldom assessed. We characterized the aquatic, semi‐aquatic, and terrestrial macroinvertebrate communities in remnant, uninvaded marsh to identify restoration targets and compared this to the communities in Phragmites australis‐invaded marsh and in the formerly invaded marsh that was treated with the herbicide glyphosate in 2016 to simultaneously evaluate the effects of invasion and invasive‐species suppression. We sampled invertebrates in 2017 and 2018 to track 2 years following herbicide treatment. The invertebrate community composition was similar between P. australis invaded and remnant marsh, suggesting invasion has little effect on macroinvertebrate community structure. There was also high concordance between the aquatic and emerging‐invertebrate communities in the invaded and uninvaded habitats. In contrast, herbicide‐treated sites had a unique community composition, characterized by very high densities of Chironomidae (Diptera) and low taxa richness and evenness. Herbicide‐treated sites also exhibited low concordance between the aquatic and emerging‐invertebrate communities, potentially attributable to the sparse, emergent‐vegetation cover providing limited substrates for emergence. Herbicide‐based, invasive‐species control resulted in considerable changes to the macroinvertebrate community in freshwater marshes for at least 2 years after treatment, which may have consequences for aquatic food webs and species that rely on macroinvertebrates as prey. [ABSTRACT FROM AUTHOR]

Droughts can affect invertebrate communities in wetlands, which can have bottom-up effects on the condition and survival of top predators. Shorebirds, key predators at coastal wetlands, have experienced widespread population declines and could be negatively affected by droughts. We explored, in detail, the effects of drought on multiple aspects of shorebird stopover and migration ecology by contrasting a year with average wet/dry conditions (2016) with a year with moderate drought (2017) at a major subarctic stopover site on southbound migration. We also examined the effects of drought on shorebird body mass during stopover across 14 years (historical: 1974–1982 and present-day: 2014–2018). For the detailed comparison of two years, in the year with moderate drought we documented lower invertebrate abundance at some sites, higher prey family richness in shorebird faecal samples, lower shorebird refuelling rates, shorter stopover durations for juveniles, and, for most species, a higher probability of making a subsequent stopover in North America after departing the subarctic, compared to the year with average wet/dry conditions. In the 14-year dataset, shorebird body mass tended to be lower in drier years. We show that even short-term, moderate drought conditions can negatively affect shorebird refuelling performance at coastal wetlands, which may carry-over to affect subsequent stopover decisions. Given shorebird population declines and predicted changes in the severity and duration of droughts with climate change, researchers should prioritize a better understanding of how droughts affect shorebird refuelling performance and survival. [ABSTRACT FROM AUTHOR]

Regulated rivers downstream of dams often exhibit highly modified thermal regimes in addition to modified hydrologic regimes; downstream river temperatures can be seasonally much warmer or cooler than unregulated streams. Selective water withdrawals can be used to minimize thermal impacts to downstream reaches. However, other water quality parameters, in‐reservoir production, and species composition also vary with depth. In the South Fork McKenzie River, in the Pacific Northwest of North America, an existing large dam was retrofitted to mix and export water from multiple depths, allowing dam operators to adjust the outflow temperatures to be in sync with the upstream thermal regime. We examined benthic macroinvertebrate responses after implementation of selective water withdrawal, comparing it to thermally similar flow‐through conditions, expecting to see shifts in the community over time to resemble upstream, undammed reaches. However, species composition and traits downstream of the dam became more dissimilar to upstream and to flow‐through after selective water withdrawal. These changes included increases in non‐insect taxa and taxa known to feed on plankton and detritus. The most likely explanation for this transition is that selective water withdrawal from multiple depths of a stratified reservoir included epilimnetic releases, which resulted in increased export of plankton and organic material downstream. This strategy favored taxa able to capitalize on resource subsidies from the reservoir. Our findings highlight the interconnected nature of responses to dams and dam operations, including the importance of considering biotic communities in addition to temperature and flow when planning water management strategies. Plain Language Summary: Large dams form deep reservoirs that are often stratified in summer, warm at the surface and cold at depth. When water is released from one depth, there can be dramatic shifts in downstream water temperatures and impacts to instream ecological communities. To remedy this, dams are being retrofitted to release water from multiple reservoir depths. We studied stream invertebrates upstream and downstream of a dam where modifications allowed the release of water from multiple depths to match upstream water temperatures, comparing this to flow‐through conditions. We expected to see increasing similarity between the invertebrate communities at the downstream and the upstream reference site. However, when the dam released water from multiple depths of a stratified reservoir, we observed shifts toward non‐insects and a persistent reduction in the densities of downstream invertebrates. The unplanned export of non‐insect plankton and other material from the surface waters of the reservoir can affect downstream food webs. Our findings highlight that changes to naturalize the downstream water temperatures can have unexpected impacts and lead to shifts in the instream invertebrate communities. This means that, in addition to temperature and flow, consideration of species responses would be important when planning thermal restoration for outflows from reservoirs. Key Points: Selective water withdrawal designed to reduce the impacts of reservoirs can result in unintended consequences for downstream communitiesAfter selective withdrawal, downstream benthic macroinvertebrate communities had more non‐insect and filter‐feeding taxaThis highlights the interconnected nature of water quality parameters and the importance of anticipating biotic responses [ABSTRACT FROM AUTHOR]

Rare, long‐distance dispersal events are a key process in generating and maintaining patterns in biological diversity and species distributions across space and time. The 9.0 magnitude earthquake that struck the eastern coast of Japan in 2011, and the subsequent 38 m high tsunami washed large amounts of shoreline debris into the Pacific Ocean that led to a large‐scale biological rafting event carrying nearly 300 marine species to the western shores of North America. Whether oceanic, trans‐Pacific dispersal via rafting generates long distance dispersal events for small, flightless, terrestrial species is unknown. By sampling beach debris associated with known hot‐spots of tsunami debris along the north and east shores of Graham Island, Haida Gwaii, Canada, I document significantly dissimilar invertebrate communities associated with tide‐line beach debris and the occurrence of several putative Japanese species of soil‐dwelling mites (Acari: Oribatida). Previous explanations of Haida Gwaii's unique flora and fauna have been attributed to a proximity to the Beringian land bridge and the accumulated evidence of near‐offshore glacial refugia during the last glacial period. However, my research also suggests that stochastic, trans‐Pacific rafting events contribute to the biodiversity and biogeography of soil communities on the west coast of North America. [ABSTRACT FROM AUTHOR]

In recent decades, oyster reefs have been deteriorating throughout North America as a result of multiple interacting anthropogenic stressors, including pesticide pollution. Here we elucidated the potential chronic effects of the commonly utilized pesticide, carbaryl, on oyster reef communities in the Loxahatchee River Estuary in southeast Florida. Though carbaryl had a limited effect on total epifaunal community diversity, species richness and evenness, the results of this experiment indicate that carbaryl significantly shifted crustacean community composition, resulting in a substantial loss in total crustacean abundance. One crustacean in particular, Americorophium spp. (tube building amphipod), was significantly less abundant within the carbaryl treatment, driving the shift in crustacean community composition. Ultimately, our results signal that pesticide pollution in estuaries will negatively impact crustaceans. Over time, this may shift benthic community composition, potentially disrupting species interactions and threatening valuable economic and ecosystem services. • Carbaryl additions resulted in reduced crustacean abundance on oyster reefs • Carbaryl exerted no visible effects on epifaunal community diversity, species richness or evenness within the oyster reef communities • Americorophium spp. abundance was significantly lower within carbaryl treatments, indicating a potential sensitivity to pesticide pollution • Pesticide pollution in estuaries may influence the structure of benthic invertebrate communities over time [ABSTRACT FROM AUTHOR]

Earthworms are invading soil communities worldwide, and their actions as decomposers and ecosystem engineers are vastly impacting many ecosystem functions. In the northern regions of North America, invasive earthworms are often functionally distinct from the native invertebrate fauna and, thus, typically occupy empty trophic niches in soil food webs. Nevertheless, they can affect the co-occurring soil invertebrate communities in multiple indirect ways. Particularly, the redistribution and removal of litter resources can affect feeding interactions of soil biota that channel up to higher trophic levels, such as predators, causing shifts across all components of the soil food web, which are hard to investigate. To study trophic shifts in earthworm-invaded soil communities, we used ground predators as model organisms since they occupy high trophic levels and connect different energy channels in soil food webs. We used stable isotope (13C and 15N) and fatty acid analyses as complementary tools to describe the trophic levels and basal resources of consumers that were impacted by earthworm invasion, specifically examining the trophic niches and resources available to ground-dwelling invertebrates of a northern aspen forest. The distinct trophic niches of invertebrate species were affected significantly by earthworm invasion. Shifts in neutral lipid fatty acid profiles as well as decreases in animal Δ13C and Δ15N signatures indicated changes in basal resources and trophic levels, respectively. Furthermore, we observed a trend of greater intra-specific and less inter-specific variation in fatty acid profiles of soil organisms following earthworm invasion. Notably, shifts in marker fatty acids of ground-dwelling invertebrates were opposite to the changes observed in soil microbial communities, suggesting de-coupling of soil microbial and ground arthropod food-web compartments. Overall, our study revealed a systemic effect of invasive earthworms on ground-dwelling invertebrates. Earthworms presumably consumed a considerable amount of resources, such as litter and, thus, incorporated them in the soil food web, which was, as a basal resource, not available in the food web free of earthworms. Overall, the ground-dwelling invertebrates have adapted (changed their trophic function) which could explain the balancing of potential environmental changes that are caused by invasive earthworms. This observation potentially explains why these species are dominant in the studied forest and resist earthworm invasion. Future studies should investigate if altered litter availability also causes shifts in soil biodiversity in invaded forests, which is assumed but rarely directly tested to date. • Earthworms are invading soil communities worldwide with vast impacts on ecosystems. • We investigated trophic niches in soil communities with earthworm invasion. • We combined stable isotope and fatty acid analyses as complementary tools. • We found that earthworms incorporated litter resources in the soil food web. • Intra-specific variation in niches increased and inter-specific variation decreased. [ABSTRACT FROM AUTHOR]

The primary defense mechanism of the North American millipede, Orthoporus texicolens, is coiling. We studied habituation, a form of non-associative learning, by observing coiling in response to a vibrational stimulus. Coiling declined in successive trials, indicating that habituation occurred. Dishabituation was then studied by not presenting the vibrational stimulus for intervals ranging from 4-14 minutes. The response of coiling did begin to reappear, showing evidence of dishabituation. Of the experimental millipedes, 75% habituated to vibrational stimuli, and of these millipedes, 100% dishabituated due to the lengthening time span between each vibrational period. Our data indicate that millipedes are able to habituate to a stimulus and then dishabituate to the stimulus if the time intervals between stimulus presentation are lengthened. [ABSTRACT FROM AUTHOR]

Simple Summary: Spiders contribute greatly to biodiversity and play important roles in terrestrial food webs, yet we know very little about the types of spiders that live in semi-arid grasslands in the Pacific Northwest, USA. As interest in the conservation of biodiversity and restoration of these imperiled ecosystems grows, it is imperative that we not only describe spider communities (i.e., groups of interacting species) in these areas, but also investigate environmental factors that influence them, and how they respond to restoration. This information can help guide land managers as they design restoration and management plans. Our goals were threefold: (1) describe variability in spider communities in three semi-arid grasslands of the Pacific Northwest, (2) identify environmental variables that may influence spider communities, and (3) determine whether spiders or environmental variables differ between actively vs. passively restored sites. We found that spider communities varied greatly among three superficially similar locations and patterns corresponded to differences in elevation and cover of invasive grass, litter, biological soil crust, and flowering plants. We found no differences between spider communities in active and passive restoration treatments, indicating that if the primary goal of restoration is to increase biodiversity, additional factors must also be manipulated. Grassland restoration in North America has intensified but its impact on major invertebrate groups, including spiders, is unclear. We studied three grassland locations in the Pacific Northwest, USA, to (1) describe variability in spider communities, (2) identify environmental variables that may underlie patterns in spider communities, and (3) determine whether spiders and environmental variables differ between actively (removal of disturbances, then plant with natives) vs. passively restored sites (removal of disturbance only). We found spider richness, diversity, and composition differed among the three locations but abundance did not. Sites with more litter and invasive grass cover had more spiders while sites at higher elevation and with more forb and biological soil crust cover had increased spider richness and diversity. Spider community composition was associated with elevation and litter cover. Surprisingly, no spider community or environmental variables differed between actively and passively restored sites, except that litter cover was higher in passively restored sites. This study demonstrates that even in superficially similar locations, invertebrate communities may differ greatly and these differences may prevent consistent responses to active vs. passive restoration. If increasing biodiversity or the abundance of invertebrate prey are goals, then environmental factors influencing spider communities should be taken into account in restoration planning. [ABSTRACT FROM AUTHOR]