Variable consumer responses to invasion by Microstegium vimineum: The role of indirect effects

*Background/Question/Methods*
As both basal resources and autogenic ecosystem engineers, plants play an important role in structuring consumer communities. Plant invasion can alter important ecosystem properties such as habitat complexity, nutrient availability, and abiotic properties, and the hyper-productive, high-nutrient nature of many invaders may make the influence of these plants especially pronounced. While direct influences of these processes on competitors and predators may be relatively foreseeable, the consequences of indirect effects on consumers living within these invaded habitats are more difficult to predict. In order to determine the response of various forest floor consumers to invasion by the exotic grass _Microstegium vimineum_ we stocked large enclosures spanning eight independent invasion fronts with metamorphic individuals of three amphibian species; _Anaxyrus [Bufo] americanus_ (American toads), _Lithobates [Rana] sphenocephalus_ (southern leopard frogs), and _Notophthalmus viridescens_ (eastern newts). Using robust capture periods we tracked the survival and growth of these individuals. We also investigated the mechanisms behind these responses by tracking invertebrate abundance and abiotic factors on either side of each of these invasion fronts and performing additional manipulations, such as predator manipulations and analyses of foraging success, designed to investigate the effects of both bottom-up and top-down influences on these consumers.

*Results/Conclusions*
We found that invasion by _M. vimineum_ could have significant effects on consumer performance (for example, the survival of metamorphic _A. americanus_ was significantly lower in invaded areas) but that the nature and strength of these influences varied between species as well as ontogenetically, as _L. sphenocephalus_ was not similarly affected and the influences on _A. americanus_ dissipated over time. It appears that the negative influences of invasion on metamorphic toad survival were largely driven by top-down processes associated with the accumulation of invertebrate predators in invaded areas, while abiotic and bottom-up influences were more important factors for individuals large or fast enough to escape capture by invertebrate predators. We conclude that the influences of plant invasion on consumer communities can be varied, complicated, and far-reaching

Spatial ecology of cane toads (Rhinella marina) in their native range: a radiotelemetric study from French Guiana

Like most invasive species, cane toads have attracted less research in their native range than in invaded areas. We radio-tracked 34 free-ranging toads in French Guiana, a source region for most invasive populations, across two coastal and two rainforest sites. Coastal toads generally sheltered in pools of fresh or brackish water but nocturnally foraged on beaches, whereas rainforest toads sheltered in forested habitats, moving into open areas at night. Over five days of monitoring, native toads frequently re-used shelters and moved little between days (means = 10–63 m/site) compared to invasion-front toads from Australia (~ 250 m). Larger toads moved less between days, but displaced in more consistent directions. At night, foraging toads travelled up to 200 m before returning to shelters. Foraging distance was related to body condition at coastal sites, with toads in poorer body condition travelling farther. Rain increased the probability of coastal toads sheltering in the dry habitats where they foraged. Dispersal and rainfall were lower at coastal sites, and the strategies utilized by coastal toads to minimize water loss resembled those of invasive toads in semi-desert habitats. This global invader already exhibits a broad environmental niche and substantial behavioural flexibility within its native range

An Evaluation of Feral Cat Management Options Using a Decision Analysis Network

The feral domestic cat (Felis catus) is a predatory invasive species with documented negative effects on native wildlife. The issue of appropriate and acceptable feral cat management is a matter of contentious debate in cities and states across the United States due to concerns for wildlife conservation, cat welfare, and public health. Common management strategies include: Trap-Neuter-Release, Trap-Neuter-Release with removal of kittens for adoption and Trap-Euthanize. Very little empirical evidence exists relevant to the efficacy of alternative options and a model-based approach is needed to predict population response and extend calculations to impact on wildlife. We have created a structured decision support model representing multiple stakeholder groups to facilitate the coordinated management of feral cats. We used a probabilistic graphical model (a Bayesian Belief Network) to evaluate and rank alternative management decisions according to efficacy, societal preferences, and cost. Our model predicts that Trap-Neuter-Release strategies would be optimal management decisions for small local populations of less than fifty cats while Trap-Euthanize would be the optimal management decision for populations greater than 50 cats. Removal is predicted to reduce feral cat populations quickly and prevent cats from taking a large number of wildlife prey

Mechanisms, costs, and carry‐over effects of cannibal‐induced developmental plasticity in invasive cane toads

Abstract Inducible defences can improve survival in variable environments by allowing individuals to produce defences if they detect predators. These defences are often expressed as inter‐related developmental, morphological, and behavioural changes. However, producing defences can incur costs, which may be expressed immediately and/or during subsequent life stages. In Australia, waterborne cues of potentially cannibalistic conspecific tadpoles induce hatchlings of invasive cane toads to accelerate their developmental rate, thereby reducing their window of vulnerability. However, the mechanisms and costs of such accelerated development are poorly understood, and whether cane toad embryos show cannibal‐induced plasticity in other traits is unknown. Here, we found no evidence of altered time of hatching for embryos exposed to non‐feeding conspecific cannibal tadpole cues. Additionally, hatchling dispersal behaviours were not affected by exposure to these cues. However, developmental acceleration of hatchlings induced by exposure to tadpole cues was accompanied by reduced hatchling growth, indicating a trade‐off between these processes. At the conclusion of the hatchling stage, cannibal‐exposed individuals were smaller and morphologically distinct from control siblings. This size reduction affected performance during the subsequent tadpole stage: smaller cannibal‐exposed individuals were more likely to die, and initial size tended to be positively associated with subsequent tadpole growth and development across treatments (respectively, p = .07 and p = .06). However, even accounting for variation in initial size, there was an additional negative effect of cannibal exposure on tadpole growth and development, demonstrating that the fitness costs associated with developmental acceleration are not entirely attributable to size reductions

Wikis in the classroom: Properties and potential uses of this collaborative learning tool

Background/Question/Methods 
Student engagement is tied to course performance and information retention. Shifting the focus of the classroom from a lecture-based approach to a student-centered learning environment is one way to achieve this goal. One tool that can be used to allow student contribution to the content and direction of a course is a wiki. Wikis are highly flexible collaborative websites that can be structured to meet course needs and allow multiple users to contribute to site content. They provide a platform where real-time editing can be performed in a flexible 'topical' format. They are intended to promote group learning through collaboration rather than isolated reflection, and can provide another avenue through which instructors can connect with various types of learners through multimedia learning. 

Results/Conclusions 
We will present multiple ways in which wikis can be used in the classroom, such as collaborative projects, peer review, debates, competitions, and student comments and reflections on course material. Within these contexts faculty can promote the use of multimedia and creativity within student work and enable peer learning through public project viewing. They also track each student’s edits and additions to site content, allowing for instructor assessment of an individual’s contributions to group progress. We have found that the use of the wiki format promoted class participation, a sense of community within the course in question, and a feeling of project ownership and accomplishment

Appendix C. Tabular results for statistical analyses and a scatterplot depicting toad survival within the field cages.

Tabular results for statistical analyses and a scatterplot depicting toad survival within the field cages

Appendix B. Description of the methods used in site selection, the installation of field enclosures, and the production and recapture of toads.

Description of the methods used in site selection, the installation of field enclosures, and the production and recapture of toads

Appendix A. Study site information, including photographs of study organisms and representative field sites.

Study site information, including photographs of study organisms and representative field sites

The evolution of targeted cannibalism and cannibal-induced defenses in invasive populations of cane toads

Biotic conflict can create evolutionary arms races, in which innovation in one group increases selective pressure on another, such that organisms must constantly adapt to maintain the same level of fitness. In some cases, this process is driven by conflict among members of the same species. Intraspecific conflict can be an especially important selective force in high-density invasive populations, which may favor the evolution of strategies for outcompeting or eliminating conspecifics. Cannibalism is one such strategy; by killing and consuming their intraspecific competitors, cannibals enhance their own performance. Cannibalistic behaviors may therefore be favored in invasive populations. Here, we show that cane toad tadpoles (Rhinella marina) from invasive Australian populations have evolved an increased propensity to cannibalize younger conspecifics as well as a unique adaptation to cannibalism-a strong attraction to vulnerable hatchlings-that is absent in the native range. In response, vulnerable conspecifics from invasive populations have evolved both stronger constitutive defenses and greater cannibal-induced plastic responses than their native range counterparts (i.e., rapid prefeeding development and inducible developmental acceleration). These inducible defenses are costly, incurring performance reductions during the subsequent life stage, explaining why plasticity is limited in native populations where hatchlings are not targeted by cannibalistic tadpoles. These results demonstrate the importance of intraspecific conflict in driving rapid evolution, highlight how plasticity can facilitate adaptation following shifts in selective pressure, and show that evolutionary processes can produce mechanisms that regulate invasive populations