Effects of an Invasive Plant on Population Dynamics in Toads

When populations decline in response to unfavorable environmental change, the dynamics of their population growth shift. In populations that normally exhibit high levels of variation in recruitment and abundance, as do many amphibians, declines may be difficult to identify from natural fluctuations in abundance. However, the onset of declines may be evident from changes in population growth rate in sufficiently long time series of population data. With data from 23 years of study of a population of Fowler's toad (Anaxyrus [ = Bufo] fowleri) at Long Point, Ontario (1989–2011), we sought to identify such a shift in dynamics. We tested for trends in abundance to detect a change point in population dynamics and then tested among competing population models to identify associated intrinsic and extrinsic factors. The most informative models of population growth included terms for toad abundance and the extent of an invasive marsh plant, the common reed (Phragmites australis), throughout the toads’ marshland breeding areas. Our results showed density‐dependent growth in the toad population from 1989 through 2002. After 2002, however, we found progressive population decline in the toads associated with the spread of common reeds and consequent loss of toad breeding habitat. This resulted in reduced recruitment and population growth despite the lack of significant loss of adult habitat. Our results underscore the value of using long‐term time series to identify shifts in population dynamics coincident with the advent of population decline. Efectos de una Planta Invasora sobre las Dinámica Poblacional de Sapos     

Understanding and Estimating Effective Population Size for Practical Application in Marine Species Management

Abstract: Effective population size (N_e) determines the strength of genetic drift in a population and has long been recognized as an important parameter for evaluating conservation status and threats to genetic health of populations. Specifically, an estimate of N_e is crucial to management because it integrates genetic effects with the life history of the species, allowing for predictions of a population's current and future viability. Nevertheless, compared with ecological and demographic parameters, N_e has had limited influence on species management, beyond its application in very small populations. Recent developments have substantially improved N_e estimation; however, some obstacles remain for the practical application of N_e estimates. For example, the need to define the spatial and temporal scale of measurement makes the concept complex and sometimes difficult to interpret. We reviewed approaches to estimation of N_e over both long‐term and contemporary time frames, clarifying their interpretations with respect to local populations and the global metapopulation. We describe multiple experimental factors affecting robustness of contemporary N_e estimates and suggest that different sampling designs can be combined to compare largely independent measures of N_e for improved confidence in the result. Large populations with moderate gene flow pose the greatest challenges to robust estimation of contemporary N_e and require careful consideration of sampling and analysis to minimize estimator bias. We emphasize the practical utility of estimating N_e by highlighting its relevance to the adaptive potential of a population and describing applications in management of marine populations, where the focus is not always on critically endangered populations. Two cases discussed include the mechanisms generating N_e estimates many orders of magnitude lower than census N in harvested marine fishes and the predicted reduction in N_e from hatchery‐based population supplementation.     

Modeling Species' Distributions to Improve Conservation in Semiurban Landscapes: Koala Case Study

Abstract:  Models of species' distributions are commonly used to inform landscape and conservation planning. In urban and semiurban landscapes, the distributions of species are determined by a combination of natural habitat and anthropogenic impacts. Understanding the spatial influence of these two processes is crucial for making spatially explicit decisions about conservation actions. We present a logistic regression model for the distribution of koalas (  Phascolarctos cinereus ) in a semiurban landscape in eastern Australia that explicitly separates the effect of natural habitat quality and anthropogenic impacts on koala distributions. We achieved this by comparing the predicted distributions from the model with what the predicted distributions would have been if anthropogenic variables were at their mean values. Similar approaches have relied on making predictions assuming anthropogenic variables are zero, which will be unreliable if the training data set does not include anthropogenic variables close to zero. Our approach is novel because it can be applied to landscapes where anthropogenic variables are never close to zero. Our model showed that, averaged across the study area, natural habitat was the main determinant of koala presence. At a local scale, however, anthropogenic impacts could be more important, with consequent implications for conservation planning. We demonstrated that this modeling approach, combined with the visual presentation of predictions as a map, provides important information for making decisions on how different conservation actions should be spatially allocated. This method is particularly useful for areas where wildlife and human populations exist in close proximity.     

Disease Surveillance and Control After a Flood: Khartoum, Sudan, 1988

Following a flood in Khartoum, Sudan, emergency disease surveillance was implemented to monitor the health status of the population. Simple, symptom-oriented case definitions for diarrheal disease, measles, respiratory disease, malaria, and jaundice were included on the report form used to collect daily counts of outpatients in a sample of both temporary and permanent clinics located in areas of the city most affected by the flood. Data collected from major teaching hospitals allowed comparison of pre- and post-disaster levels of morbidity and mortality. In addition, special surveys collected information unobtainable from health facilities. Sentinel clinic surveillance data indicated that diarrheal disease accounted for the greatest number of clinic visits, while malaria was the second most common reason for seeking medical attention. Malaria blood smear surveys showed that the parasitemia prevalence ranged from 11% to 19% in the general population and from 21% to 46% among febrile clinic patients. Hospital admission data demonstrated an increase in morbidity from diarrhea and malaria in August 1988, when compared to previous months and August of the previous year, although it is uncertain whether this increase was due to the flood. Nutrition surveys demonstrated that 23% of young children were moderately or severely undernourished, with substantial variation by area of the city. No major outbreaks of communicable disease were detected in the 4 weeks after the flood. Disease surveillance provided data useful in identifying public health problems, setting priorities, targeting interventions and controlling rumors. Disease control measures taken by the Ministry of Health included provision of potable water, standardization of medical care, and distribution of immunizations, oral rehydration salts, and vitamin supplements to children.     

Environmental Impacts of the Emerging Digital Economy: The E-for-Environment E-Commerce?

The Internet-led digital economy is changing both the production and consumption patterns at the global scale. Although great potential exists to harness information technology in general and the Internet in particular and improve the environment, possible negative impacts of e-commerce on the environment should also be considered and dealt with. In this forum, we discuss both the potential positive and negative impacts of e-commerce. Drawing from insights gained from the complexity theory, we also delineate some broad contours for environmental policies in the information age. Given the paradoxical nature of technological innovations, we want to caution the scientific community and policymakers not to treat the Internet as the Holy Grail for environmental salvation.     

Forks in the Road: Choices in Procedures for Designing Wildland Linkages

Abstract:  Models are commonly used to identify lands that will best maintain the ability of wildlife to move between wildland blocks through matrix lands after the remaining matrix has become incompatible with wildlife movement. We offer a roadmap of 16 choices and assumptions that arise in designing linkages to facilitate movement or gene flow of focal species between 2 or more predefined wildland blocks. We recommend designing linkages to serve multiple (rather than one) focal species likely to serve as a collective umbrella for all native species and ecological processes, explicitly acknowledging untested assumptions, and using uncertainty analysis to illustrate potential effects of model uncertainty. Such uncertainty is best displayed to stakeholders as maps of modeled linkages under different assumptions. We also recommend modeling corridor dwellers (species that require more than one generation to move their genes between wildland blocks) differently from passage species (for which an individual can move between wildland blocks within a few weeks). We identify a problem, which we call the subjective translation problem, that arises because the analyst must subjectively decide how to translate measurements of resource selection into resistance. This problem can be overcome by estimating resistance from observations of animal movement, genetic distances, or interpatch movements. There is room for substantial improvement in the procedures used to design linkages robust to climate change and in tools that allow stakeholders to compare an optimal linkage design to alternative designs that minimize costs or achieve other conservation goals.     

Factors affecting perceptions of workplace sexual harassment

This study investigated several variables that determine how one interprets another's behavior as sexually harassing in ambiguous situations. Data were collected from 1234 male and female graduate and undergraduate student subjects who responded to 24 versions of a vignette describing an interaction between a male and female who worked for the same firm (2×3×2×2 design). Variables manipulated included (1) amount of prior socializing of the man and woman; (2) job status (peer coworker, direct supervisor, executive) of harasser; (3) verbal versus touching behavior; and (4) physical setting (at computer terminal or happy hour). Results revealed several main effects such that a male's potentially harassing behavior toward a female was evaluated more negatively (1) when the pair had not previously socialized, (2) when the harasser was a supervisor or executive, (3) when it involved verbal comments, and (4) when the behavior occurred in a work (versus social) setting. Additional analysis revealed that, contrary to previous studies, there were no male–female differences among respondents in evaluations of behavior as harassing.