Species Listing under Canada's Species at Risk Act

Abstract: In a preliminary analysis of listing decisions under Canada's Species at Risk Act (SARA), Mooers et al. (2007) demonstrated an apparent bias against marine and northern species. As a follow‐up, we expanded the set of potential explanatory variables, including information on jurisdictional and administrative elements of the listing process, and considered an additional 16 species recommended for listing by SARA's scientific advisory committee as of 15 August 2006. Logistic model selection based on Akaike differences suggested that species were less likely to be listed if they were harvested or had commercial or subsistence harvesting as an explicitly identified threat; had Department of Fisheries and Oceans (DFO) as a responsible authority (RA); were located in Canada's north generally, and especially in Nunavut; or were found mostly or entirely within Canada. Subsequent model validation with an independent set of 50 species for which a listing decision was handed down in December 2007 showed an overall misclassification rate of <0.10, indicating reasonable predictive power. In light of these results, we recommend that RAs under SARA adopt a two‐track listing approach to address problems of delays arising from extended consultations and the inconsistent use by the RAs of socioeconomic analysis; consider revising SARA so that socioeconomic analysis occurs during decisions about protecting species and their habitats rather than at the listing stage; and maintain an integrated database with information on species’ biology, threats, and agency actions to enable future evaluation of SARA's impact.     

A Successful Predictive Model of Species Richness Based on Indicator Species

Abstract:  Because complete species inventories are expensive and time-consuming, scientists and land managers seek techniques to alleviate logistic constraints on measuring species richness, especially over large spatial scales. We developed a method to identify indicators of species richness that is applicable to any taxonomic group or ecosystem. In an initial case study, we found that a model based on the occurrence of five indicator species explained 88% of the deviance of species richness of 56 butterflies in a mountain range in western North America. We validated model predictions and spatial transferability of the model using independent, newly collected data from another, nearby mountain range. Predicted and observed values of butterfly species richness were highly correlated with 93% of the observed values falling within the 95% credible intervals of the predictions. We used a Bayesian approach to update the initial model with both the model-building and model-validation data sets. In the updated model, the effectiveness of three of the five indicator species was similar, whereas the effectiveness of two species was reduced. The latter species had more erratic distributions in the validation data set than in the original model-building data set. This objective method for identifying indicators of species richness could substantially enhance our ability to conduct large-scale ecological assessments of any group of animals or plants in any geographic region and to make effective conservation decisions.     

The Use of Species Accumulation Functions for the Prediction of Species Richness

We develop a stochastic theory of the accumulation of new species in faunistic or floristic inventories. Differential equations for the expected list size and its variance as a function of the time spent collecting are presented and solved for particular cases. These particular cases correspond to different models of how the probability of adding a new species changes with time, the size of the list, the complexity of the area sampled, and other parameters. Examples using field data from butterflies and mammals are discussed, and it is argued that the equations relating sampling effort with size of the list may be useful for conservation purposes because they should lend formality to comparisons among lists and because they may have predictive power by extrapolating the asymptotic size of the lists. The suitability of different models to a variety of field situations is also discussed.     

Assessing the Risk of Introducing Exotic Species via the Live Marine Species Trade

Abstract:  Although the shipping industry has received considerable attention as a dispersal mechanism for aquatic nuisance species, many invasions have been linked to other mechanisms of transfer. The threat posed to coastal ecosystems by these alternative mechanisms, however, remains largely unquantified. We assessed the potential risks of introducing marine and estuarine species associated with seven mechanisms of transfer: seafood companies, aquaculture operations, bait shops, stores that sell marine ornamental species, research and educational organizations, public aquariums, and coastal restoration projects. For each, we compiled a comprehensive database of organizations in coastal Massachusetts. We then designed and administered a survey to a subset of organizations that inquired about (1) their proximity to saltwater and methods of handling live imports; (2) the type and quantity of marine species being imported; and (3) the organization's familiarity with marine invasions. Respondents in five of the seven categories acknowledged importing nonlocal live marine species to the area. Seafood companies handled the majority of individuals but relatively few taxa. This mechanism of transfer also had the most complex trade patterns and the greatest number of operations located near saltwater. In contrast, the other transfer mechanisms each had simpler trade pathways and fewer operations but varied in the quantity and taxonomic diversity of their imports. Significantly, no single mechanism of transfer stood out as presenting a primary risk. Rather, each had characteristics or used handling practices at different points in the importation process that could facilitate introductions. To prevent future marine invasions, better reporting requirements for live species imports are needed, and best-management practices and outreach strategies specific to the transfer mechanism should be developed and implemented.     

Managing Aquatic Species of Conservation Concern in the Face of Climate Change and Invasive Species

Abstract:  The difficult task of managing species of conservation concern is likely to become even more challenging due to the interaction of climate change and invasive species. In addition to direct effects on habitat quality, climate change will foster the expansion of invasive species into new areas and magnify the effects of invasive species already present by altering competitive dominance, increasing predation rates, and enhancing the virulence of diseases. In some cases parapatric species may expand into new habitats and have detrimental effects that are similar to those of invading non-native species. The traditional strategy of isolating imperiled species in reserves may not be adequate if habitat conditions change beyond historic ranges or in ways that favor invasive species. The consequences of climate change will require a more active management paradigm that includes implementing habitat improvements that reduce the effects of climate change and creating migration barriers that prevent an influx of invasive species. Other management actions that should be considered include providing dispersal corridors that allow species to track environmental changes, translocating species to newly suitable habitats where migration is not possible, and developing action plans for the early detection and eradication of new invasive species.     

Species diversity modulates predation

Predation occurs in a context defined by both prey and non-prey species. At present it is largely unknown how species diversity in general, and species that are not included in a predator's diet in particular, modify predator-prey interactions. Therefore we studied how both the density and diversity of non-prey species modified predation rates in experimental microcosms. We found that even a low density of a single nonprey species depressed the asymptote of a predator's functional response. Increases in the density and diversity of non-prey species further reduced predation rates to very low levels. Controls showed that this diversity effect was not due to the identity of any of the non-prey species. Our results establish that both the density and diversity of species outside a predator's diet can significantly weaken the strength of predator-prey interactions. These results have major implications for ecological theory on species interactions in simple vs. complex communities. We discuss our findings in terms of the relationship between diversity and stability.