The Ants of Nantucket: Unexpectedly High Biodiversity in an Anthropogenic Landscape

This first comprehensive assessment of the ant fauna of Nantucket Island, Massachusetts revealed that 43% of New England ant species and 70% of New England ant genera occur on an island occupying only 0.07% of New England’s land area. Ants collected by four different research groups between 2000 and 2009 included 32,158 individual ants (2,911 incidences) from 384 spatially and temporally distinct samples representing 14 different vegetation community types. The majority of the ant species were collected from anthropogenically-derived and maintained sandplain grasslands, sandplain heathlands, and scrub oak shrublands. These three communities are state-ranked S1 community types; the lower state-ranked communities of beaches and sand dunes, bogs, salt marshes, and forest fragments had distinct ant assemblages with much lower species richness. The large number of samples described here, from a wide range of vegetation community types, expands the known list of Nantucket ant species more than three-fold and provides a baseline for future assessment of the effects of ongoing, long-term ecosystem management on Nantucket.Organismic and Evolutionary Biolog

Ecological Art: Art with a Purpose

Ecological art is purposeful and often prescriptive: the actions and directions intended by the artists for activists to undertake often are clearly represented. Yet, ecological art has been no more successful than, for example, targeted scientific research, deposits on returnable bottles, or land-protection campaigns at slowing global warming, reducing the amount of waste we generate every day, or halting the ongoing sixth mass extinction in the history of the Earth. Here, we consider the idea that prescriptive ecological art provides insufficient mental space for creative reflection about future scenarios of, and responses to, environmental change. We ask whether, by presenting a limited range of possibilities in ecological art, we limit the range of options that viewers consider in deciding on possible actions that they could take to slow or halt environmental decline. We conclude by asking how we artists and scientists can best engage diverse audiences in critically thinking about, and taking action to mitigate, environmental change. These questions and issues are addressed through a discussion of two of our recent ecological art installations: Hemlock Hospice and Warming Warning

Preserving the Picturesque: Perceptions of Landscape, Landscape Art, and Land Protection in the United States and China

The predominant environmental consciousness in both the United States and China reflects an underlying sense of separation of people from nature. Likewise, traditional landscape paintings in the United States and China share a common underlying aesthetic—i.e., the “picturesque”. Together, these similarities appear to have led to the preservation of similar types of landscapes in both countries. Because decisions regarding landscape preservation and subsequent management of preserved areas in both countries reflect aesthetic preferences more than they reflect economic values placed on ecosystem services, contemporary artists have an opportunity to help shape future societal decisions regarding what natural areas to conserve and protect.Organismic and Evolutionary Biolog

Ecophysiological Traits of Terrestrial and Aquatic Carnivorous Plants: Are the Costs and Benefits the Same?

Identification of trade-offs among physiological and morphological traits and their use in cost-benefit models and ecological or evolutionary optimization arguments have been hallmarks of ecological analysis for at least 50 years. Carnivorous plants are model systems for studying a wide range of ecophysiological and ecological processes and the application of a cost-benefit model for the evolution of carnivory by plants has provided many novel insights into trait-based cost-benefit models. Central to the cost-benefit model for the evolution of botanical carnivory is the relationship between nutrients and photosynthesis; of primary interest is how carnivorous plants efficiently obtain scarce nutrients that are supplied primarily in organic form as prey, digest and mineralize them so that they can be readily used, and allocate them to immediate versus future needs. Most carnivorous plants are terrestrial – they are rooted in sandy or peaty wetland soils – and most studies of cost-benefit trade-offs in carnivorous plants are based on terrestrial carnivorous plants. However approximately 10% of carnivorous plants are unrooted aquatic plants. In this Forum paper, we ask whether the cost-benefit model applies equally well to aquatic carnivorous plants and what general insights into trade-off models are gained by this comparison. Nutrient limitation is more pronounced in terrestrial carnivorous plants, which also have much lower growth rates and much higher ratio of dark respiration to photosynthetic rates than aquatic carnivorous plants. Phylogenetic constraints on ecophysiological trade-offs among carnivorous plants remain unexplored. Despite differences in detail, the general cost-benefit framework continues to be of great utility in understanding the evolutionary ecology of carnivorous plants. We provide a research agenda that if implemented would further our understanding of ecophysiological trade-offs in carnivorous plants and also would provide broader insights into similarities and differences between aquatic and terrestrial plants of all types.Organismic and Evolutionary BiologyOther Research Uni

Modeling foundation species in food webs

Foundation species are basal species that play an important role in determining community composition by physically structuring ecosystems and modulating ecosystem processes. Foundation species largely operate via non-trophic interactions, presenting a challenge to incorporating them into food web models. Here, we used non-linear, bioenergetic predator-prey models to explore the role of foundation species and their non-trophic effects. We explored four types of models in which the foundation species reduced the metabolic rates of species in a specific trophic position. We examined the outcomes of each of these models for six metabolic rate “treatments” in which the foundation species altered the metabolic rates of associated species by one-tenth to ten times their allometric baseline metabolic rates. For each model simulation, we looked at how foundation species influenced food web structure during community assembly and the subsequent change in food web structure when the foundation species was removed. When a foundation species lowered the metabolic rate of only basal species, the resultant webs were complex, species-rich, and robust to foundation species removals. On the other hand, when a foundation species lowered the metabolic rate of only consumer species, all species, or no species, the resultant webs were species-poor and the subsequent removal of the foundation species resulted in the further loss of species and complexity. This suggests that in nature we should look for foundation species to predominantly facilitate basal species.Organismic and Evolutionary Biolog

Targeted Sampling Increases Knowledge and Improves Estimates of Ant Species Richness in Rhode Island

Only 0.7% of 28,205 known New England ant specimens (1861–2011) were from Rhode Island. Consequently, apparent ant species richness of Rhode Island counties was lower than expected based on simple biogeographic models. Collections from two poorly sampled areas—Block Island and Tiverton—and from the 2013 Rhode Island Natural History Survey's BioBlitz increased Rhode Island's ant specimens by 46%) and its ant species richness from 48 to 57. Both Washington and Newport counties now have ant species richness more in line with New England-wide species-environment predictions. The extrapolated number of Rhode Island ant species is 66, but the upper bound of the 95% confidence interval is 93 species and the total species accumulation curve has not reached an asymptote. Future collection efforts should continue to add ant species to the Rhode Island list, especially if collections are targeted in the state's north and southeast regions, and its southwest pine barrens.Organismic and Evolutionary Biolog

Food-Web Models Predict Species Abundances in Response to Habitat Change

Plant and animal population sizes inevitably change following habitat loss, but the mechanisms underlying these changes are poorly understood. We experimentally altered habitat volume and eliminated top trophic levels of the food web of invertebrates that inhabit rain-filled leaves of the carnivorous pitcher plant Sarracenia purpurea. Path models that incorporated food-web structure better predicted population sizes of food-web constituents than did simple keystone species models, models that included only autecological responses to habitat volume, or models including both food-web structure and habitat volume. These results provide the first experimental confirmation that trophic structure can determine species abundances in the face of habitat loss.Organismic and Evolutionary Biolog

The Relative Contributions of Seed Bank, Seed Rain, and Understory Vegetation Dynamics to the Reorganization of Tsuga Canadensis Forests After Loss due to Logging or Simulated Attack by Adelges tsugae

Profound changes are occurring in forests as native insects, nonnative insects, or pathogens irrupt on foundation tree species; comprehensive models of vegetation responses are needed to predict future forest composition. We experimentally simulated hemlock woolly adelgid (Adelges tsugae Annand) infestation (by girdling trees) and preemptive logging of eastern hemlock (Tsuga canadensis (L.) Carrière) and compared vegetation dynamics in replicate 90 m × 90 m treatment plots and intact hemlock stands from 2004 to 2010. Using Chao–Sørensen abundance-based similarity indices, we assessed compositional similarities of trees, shrubs, forbs, and graminoids among the seed bank, seed rain, and standing vegetation over time and among treatments. Post-treatment seed rain, similar among treatments, closely reflected canopy tree composition. Species richness of the seed bank was similar in 2004 and 2010. Standing vegetation in the hemlock controls remained dissimilar from the seed bank, reflecting suppressed germination. Recruits from the seed rain and seed bank dominated standing vegetation in the logged treatment, whereas regeneration of vegetation from the seed bank and seed rain was slowed due to shading by dying hemlocks in the girdled treatment. Our approach uniquely integrates multiple regeneration components through time and provides a method for predicting forest dynamics following loss of foundation tree species.Organismic and Evolutionary BiologyOther Research Uni

Organic-Matter Loading Determines Regime Shifts and Alternative States in an Aquatic Ecosystem

Slow changes in underlying state variables can lead to “tipping points,” rapid transitions between alternative states (“regime shifts”) in a wide range of complex systems. Tipping points and regime shifts routinely are documented retrospectively in long time series of observational data. Experimental induction of tipping points and regime shifts is rare, but could lead to new methods for detecting impending tipping points and forestalling regime shifts. By using controlled additions of detrital organic matter (dried, ground arthropod prey), we experimentally induced a shift from aerobic to anaerobic states in a miniature aquatic ecosystem: the self-contained pools that form in leaves of the carnivorous northern pitcher plant, Sarracenia purpurea. In unfed controls, the concentration of dissolved oxygen ($[O_2]$) in all replicates exhibited regular diurnal cycles associated with daytime photosynthesis and nocturnal plant respiration. In low prey-addition treatments, the regular diurnal cycles of $[O_2]$ were disrupted, but a regime shift was not detected. In high prey-addition treatments, the variance of the $[O_2]$ time series increased until the system tipped from an aerobic to an anaerobic state. In these treatments, replicate $[O_2]$ time series predictably crossed a tipping point at ∼45 h as $[O_2]$ was decoupled from diurnal cycles of photosynthesis and respiration. Increasing organic-matter loading led to predictable changes in $[O_2]$ dynamics, with high loading consistently driving the system past a well-defined tipping point. The Sarracenia microecosystem functions as a tractable experimental system in which to explore the forecasting and management of tipping points and alternative regimes.Organismic and Evolutionary Biolog