Online but not remote: Adapting field-based ecology laboratories for online learning.

Teaching ecology effectively and experientially has become more challenging for at least two reasons today. Most experiences of our students are urban, and we now face the near immediate and continuing need to deliver courses (either partially or wholly) online because of COVID-19. Therefore, providing a learning experience that connects students to their environment within an ecological framework remains crucial and perhaps therapeutic to mental health. Here, we describe how prior to the pandemic we adapted our field-based laboratories to include data collection, analysis, and interpretation, along with the development of a citizen-science approach for online delivery. This design is simple to implement, does not require extensive work, and maintains the veracity of original learning outcomes. Collaboration online following field data collection in ecology courses within the context of cities offers further options to adapt to student experience levels, resource availability, and accessibility, as well as bringing instructors and students together to build an open well-curated data set that can be used in ecology courses where no laboratories are available. Finally, it promotes an open collaboration among ecology instructors that can drive lasting conversations about ecology curriculum.

Does local isolation allow an invasive thistle to escape enemy pressure?

Enemy release often is invoked to explain the success of invasive plants: an invader benefits from reduced attack as it escapes specialized enemies through the invasion process. Enemy release typically is thought of as occurring at large geographic scales, but local-scale interactions may also be important for invader establishment and success. Furthermore, most tests of local enemy release have been conducted over a single year even though release may be a transient phenomenon, especially at small scales. In this study, we used a multi-year field experiment to investigate whether locally isolated populations of the noxious non-native weed Cirsium arvense benefit from reduced levels of aboveground damage, and whether any initial advantage is lost over subsequent growing seasons. Populations of C. arvense were grown in plots at set distances from established source populations for 4 years. In the first year of the experiment, folivory significantly declined with host isolation, but damage from specialist stem gallers and seed predators did not. However, in subsequent years of observation, folivores began colonizing isolated C. arvense populations while stem gallers exhibited very slow colonization of more isolated plots; seed predation showed no pattern with distance in any year. Local enemy escape did not result in increased plant performance, which instead negatively correlated with degree of isolation. Nonetheless, our results stress the importance of multi-year observations in tests of enemy release, since the herbivory patterns initially observed often changed within subsequent years depending on the dispersal ability and biology of the causal organism involved.

Comparative impacts of aboveground and belowground enemies on an invasive thistle.

Most research examining how herbivores and pathogens affect performance of invasive plants focuses on aboveground interactions. Although important, the role of belowground communities remains poorly understood, and the relative impact of aboveground and belowground interactions is still debated. As well, most studies of belowground interactions have been carried out in controlled environments, so little is known about the role of these interactions under natural conditions or how these relationships may change across a plant's range. Using the invasive plant Cirsium arvense, we performed a reciprocal transplant experiment to test the relative impacts of above- and belowground interactions at three sites across a 509-km latitudinal gradient in its invaded range in Ontario, Canada. At each site, C. arvense seedlings were protected with above- and/or belowground exclosures in a factorial design. Plant performance (biomass, height, stem thickness, number of leaves, length of longest leaf, maximum rhizome length) was greatest when both above- and belowground exclosures were applied and lowest when no exclosures were applied. When only one type of exclosure was applied, biomass generally improved more with belowground exclosures than with aboveground exclosures. Despite site-to-site differences in foliar damage, root damage, and mesofaunal populations, belowground interactions generally had a greater negative impact on performance than aboveground herbivory alone. These results stress the importance of including both aboveground enemy interactions and plant-soil interactions in studies of plant community dynamics and invader performance.

Sources of Controversy Surrounding Latitudinal Patterns in Herbivory and Defense.

Both herbivory and plant defenses against herbivores have been predicted to increase toward tropical regions. Early tests of this latitudinal herbivory-defense hypothesis (LHDH) were supportive, but accumulating evidence has been mixed. We argue that the lack of clarity might be due to heterogeneity in methodology and problems with study design and interpretation. We suggest possible solutions. Latitudinal studies need to carefully consider spatial and phylogenetic scale, to link plant defense measurements to herbivore performance, and to incorporate additional concepts from plant defense theory such as tolerance and induced defense. In addition, we call for consistent measures of herbivory to standardize comparisons across biomes. Improving methodology in future studies of LHDH should resolve much of the current controversy.