Montana E. Airey

Littoral habitat is an important organizing force in lacustrine food webs. Modification of littoral habitat directly impacts aquatic macroinvertebrates, which are important vectors between basal resources and higher trophic levels. Lakeshore residential development is a pervasive phenomenon often characterized by the loss of coarse woody habitat (CWH) from lakes, and the construction of artificial wooden structures (docks and ramps). To characterize the effects of artificial wooden structures on macroinvertebrate spatial distributions, we surveyed assemblages across a lightly developed lake in New York’s Adirondack Park. Using benthic sweeps and Hester-Dendy samplers, we sampled assemblages at both natural CWH and artificial wooden structures (boat ramps), and compared them to those in adjacent, non-woody areas. We found that both CWH and artificial wooden structures facilitated larger, more complex assemblages than non-woody areas. We additionally considered general shoreline characteristics, and found only compositional effects on assemblages. We suggest that impacts on aquatic macroinvertebrates arise at a fine spatial scale, and find evidence that development-associated CWH loss drives macroinvertebrate depletion. Although CWH and artificial wooden structures are unlikely to be equivalent at whole-lake scales, macroinvertebrate depletion may be functionally alleviated at fine scales by the construction of artificial wooden structures such as ramps.

Species invasions spur costly and labor-intensive control efforts, yet even local eradication is seldom achieved. When control measures are initially effective, they may drive evolutionary adaptation that prevents full eradication, as has been documented for some chemical and biocontrol approaches. Although the intensity, directionality, and persistence of selection required to increase the frequency of resistant genotypes in complex natural ecosystems remains an open question, theory predicts that high mortality can cause life-history evolution even in the absence of a strong selective agent. Here, we use annually collected ecological and genetic data to show that rapid evolution of introduced smallmouth bass has undermined a 20-y manual suppression effort in a mid-sized lake. Despite nearly doubling annual mortality, our intensive control program produced a larger bass population dominated by young and early-maturing fish. These shifts were accompanied by large allele frequency changes in three genomic regions associated with earlier maturation and increased somatic growth. Our findings bear out the theoretical prediction that high mortality can drive evolutionary adaptation in target species. Controlling species invasions are worldwide practices that typically remove a substantial proportion of a population during each of many successive generations, hence life history adaptation may be commonplace. Such evolutionary responses could be salient in explaining the widespread failure of invasion control efforts. Genetic and phenotypic monitoring to detect cryptic adaptation and preemptive design of invader eradication programs to deliberately disrupt directional selection for resistance could improve invasion control outcomes.

Understanding the full impacts of introduced and invasive species suppression on ecological communities requires long‐term suppression experiments where native species with different life histories can reach new population equilibria. Responses documented in shorter term studies are likely to be transient. This study evaluated the abundance and size structure of 11 species of littoral fishes across 20 years in response to annual, lake‐wide removal of smallmouth bass, a non‐native predator that competes with and consumes native species. Many changes in relative abundance of species were evident from comparing community composition before, immediately after, and 20 years into the invader suppression experiment. Long‐term dynamics were classified as showing abrupt change, gradual change, or no discernible change, based on a change point analysis. Relative abundance of most fish community members increased in the year following initiation of bass removal but became more varied thereafter. After initial increases, most species declined in abundance, with some declining to near or below their pre‐experiment levels and others remaining above pre‐removal levels. Many species showed an initial decrease in body size following bass removal, indicating increased abundance of young‐of‐year, but long‐term patterns varied among species. Ongoing fluctuations of populations throughout this study indicate that the direction, tempo, and stability of population responses to removing a dominant invader are often transient. Changes in population abundance and body size across our 20‐year experiment were not correlated across species, suggesting that fish communities require many generations to achieve a new stable state following the loss or suppression of a dominant predator. Synthesis and applications. Fish community restoration efforts are rarely followed by long‐term evaluations, hence current understanding of responses to removal of introduced and invasive species may be largely based on transient dynamics. Instead, both population abundance and size structure should be documented for at least a few generations of the longest‐lived species. Insights into management outcomes of suppressing or eliminating introduced and invasive predators require accounting for demographic time lags as species interactions become restructured over long periods of time.

Invasive lionfish threaten native fishes and ecosystem health of the Atlantic, Gulf of Mexico, and Caribbean communities. Controlling their spread and population growth can be difficult given their early maturity, high fecundity, a long larval dispersal period, and preference for structure. Mitigation efforts are further complicated by the existence of large and numerous, deep water refugia. Despite the potential importance of these refugia, their connection with shallow water populations and their role in recruiting pelagic larvae is poorly understood. We examined the post-settlement dispersal patterns of invasive lionfish using δ13C and δ18O stable isotope analysis on otoliths and Bayesian stock mixture analysis. We find that there is settlement within both deep- and shallow- water habitats. It is estimated that 34.5% of the shallow-water population is composed of individuals that settled in deep-water habitat and dispersed into these shallow regions post-settlement. Only 4.1% of the deep-water population is composed of individuals that settled in shallow-water habitat before dispersing. These results demonstrate a link between deep and shallow habitats within the coastal waters of Florida, with the flow of individuals from deep to shallow water being the predominate dispersal direction of post-settlement individuals. We suggest that post-settlement dispersal can contribute to the invasion of new habitat and potentially hinder shallow-water removal efforts in currently colonized areas.

Nature provides numerous ecosystem services to people, yet the prioritization of these services often depends on the goals of various stakeholder groups. The eastern oyster ( Crassostrea virginica ) is an ecologically important species along the Gulf and Atlantic coasts of the United States, where it provides essential fish habitat and may mitigate against climatic variations in urban areas. The eastern oyster also supports a multimillion dollar aquaculture industry in coastal communities. Recent declines in eastern oyster populations, however, have spurred widespread restoration activities. Here, we look at three expert stakeholder groups (academics, nongovernmental organizations, and governmental agencies) in Rhode Island (United States) to understand how stakeholder perceptions of oyster ecosystem services differ. Stakeholders' mental models showed differences among the groups' topologies and components, although the terms “Water Quality” and “Habitat/Structural Complexity” were prioritized in all the groups. Our results suggest that there is substantial intergroup variation, but that there are common threads around which future oyster restoration and management programs can be designed. By making these mental models of ecosystem services explicit, we illuminate tacit assumptions held by different stakeholders of the oyster stakeholder community in Rhode Island. In doing so, we highlight opportunities for more efficient collaboration around commonly shared goals for sustainable social and ecological management.