Ella Daly | RENR MSc Graduate Defense Seminar

Date(s) - 04/05/2021
9:00 am - 10:00 am

Event details:  A graduate exam seminar is a presentation of the student’s final research project for their degree.

This is an ALES MSc Final Exam Seminar by Ella Daly.  This seminar is open to the general public to attend.

Thesis Topic:  Mapping a Species-level Trophic and Non-trophic Multilayer Network of Known Interactions for Boreal Tetrapods of North America

Seminar Abstract:

Mapping trophic and non-trophic species interactions and mapping ecosystem-wide ecological networks have become important research avenues in network ecology, but until recently these two avenues have been separate endeavors. Now, a framework exists to combine multiple interaction types into ‘multilayer networks’, which are mathematical graph objects that have distinct layers corresponding to different interaction types. Trophic interactions are feeding interactions that may, or may not, be lethal to one species involved. Non-trophic interactions comprise all of the ecological interactions that are not directly related to feeding, such as habitat provisioning and competition for space. This paper describes the creation and analysis of the largest scale trophic and non-trophic ecological network, focusing on the structure and importance of interactions in North America’s continental boreal forest. To date, no terrestrial ecosystem-wide network of this kind has been compiled at this scale. To do this, I compiled data of real trophic and non-trophic ecological interactions between species in the boreal forest and created a multiple interaction (multilayer) ecological network partitioned by interaction type and season. Key characteristics of the boreal forest network are also described, including the varying levels of connectance and modularity in the boreal food web and non-trophic interaction networks. The most central, or topologically important, species were also identified. The dataset contains over 400 species, most of which are only active or present in the summer months, and over 4000 recorded species interactions. The majority of interactions are trophic interactions, likely because the network focuses on tetrapods. Generalist predators, such as the great horned owl (Bubo virginianus) were the most connected species. The plants included in the network were involved in many non-trophic interactions such as provisioning of nest materials for tetrapod species. Data on non-trophic interactions in the winter months was scarce, especially for negative non-trophic interactions. This was likely due to both the types of non-trophic interactions considered for this research, a paucity of winter ecological research on non-trophic interactions, and a reduction in plant-related interactions in winter months. The connectance, level of interconnection within a network, and modularity, a measure of how well a network can be divided into clusters, of the boreal forest multilayer network were examined. The network was found to have low connectance and relatively high modularity, which are both indicative of ecological stability. The species and interactions of the boreal forest will vary with time and disturbance and this dataset could be a future reference point against which observations of qualitative network structure can be compared, which would be especially interesting for the winter network that may change disproportionately due to climate change. This network can also be used to identify important boreal species whose interactions may be of management utility or concern.