Studying historic invasions can provide insight into the ongoing invasions that threaten global biodiversity. In this study, we reconsider the impacts of Littorina littorea and Carcinus maenas on the rocky intertidal community of the Gulf of Maine. Past research using invaderremoval experiments demonstrated strong topdown effects of L. littorea on algal community structure; however, such removal experiments may overlook the long-term effects of niche shifts and local extinctions caused by invasive species. We considered how a niche-shift in the native littorine, Littorina saxatilis, may change the interpretation of L. littorea impacts. Using a factorial experiment crossing predator presence/absence with L. littorea presence/absence, we found that L. saxatilis is able to exert top-down control on ephemeral algae similar to that exerted by L. littorea and that both competition by L. littorea and predation by C. maenas have strong, negative impacts on L. saxatilis. We also found higher predation rates on protected shores and at lower tidal heights and preferential predation on L. saxatilis compared to L. littorea. While movement experiments demonstrate that behavioral response to tidal height is the proximate cause of L. saxatilis exclusion from the lower intertidal, our study suggests that the ultimate causes are the additive effects of competition from and predation by invasive species.

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Introduction Postgraduate medical education in the wake of a pandemic has sparked creativity, evolving novel platforms concordant with socially distanced learning. Inevitably, evaluation is critical in navigating improvements in content delivery. However, as culture continues to shift away from didactic teaching, students are at risk of ‘feedback overload’. We propose a novel emoji scale to facilitate rapid appraisal. Method A three-point emoji scale was developed within the novel virtual learning environment for core surgical training in the West Midlands. Engagement with the emoji system was assessed and correlated with conventional post-course questionnaires. Results The novel emoji system provided a rapid mechanism for trainees to express opinion on individual modules immediately following completion. Parallels to social media meant this modality felt familiar to trainees. Simplification of feedback permitted prompt, targeted review of modules for improvement, as opposed to laborious collection and analysis of standard post-course questionnaires. Literature review revealed limited research regarding similar emoji-based responses, or the validity of Likert or free-text based feedback systems. Conclusion As virtual learning evolves following COVID-19, feedback systems help guide evolution. Emoji-based feedback may provide the key to prompt, accessible evaluation of VLE platforms.

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