Speaker: Jenny Paige

Title: Changing Connectivity: A Spatial Understanding of Bistable Coral Dynamics

Abstract: Modeling coral ecosystems in a theoretical framework typically focuses on tradeoffs between coral, algae, and grazing fish populations, highlighting its bistable dynamics; however, spatial understanding of this system is often suppressed. Analysis of models with spatial features is crucial, as degraded, patchy reef systems become more common, and the size, clustering, or overall connectivity of these patches play a key role in the persistence and the emergent dynamics. More broadly, the implications of spatial heterogeneity and connectivity in systems with alternative stable states are complex and underexplored. In this work, we explore the long term dynamics, through both numerical and mathematical analysis, of a spatial model of a coral ecosystem, extended to multiple reef patches. Our results explore the “mixed-blessing” that connectivity can have on coral metacommunities.

Speaker: Lauren Mossman

Title: Competition for space: species zonation promotes coexistence in the rocky intertidal

Abstract: Food web models have historically focused on trophic (consumptive) interactions, disregarding the role of non-trophic (non-consumptive) interactions that are known to provide a foundation for community persistence. Key interaction types are defined with a multiplex network, in which each link type represents a different class of species interaction. We integrate the multiplex network into the ODE based Allometric Trophic Network (ATN) model which describes biomass changes over time and uses allometric scaling for parameterization. Applying this framework to the well-studied, biodiverse Chilean rocky intertidal, we focus on non-trophic interactions that modify the quantity of space available, such as competition for space and facilitative multi-species stacking. Empirically-derived competition networks based on species zonation are compared to simulated random competition networks. Across model structures, the presence of ecological refugia for sessile consumers is a key mechanism supporting species coexistence. The enhanced persistence is notable at higher trophic levels, where realistic network structures facilitate more favorable biomass distributions. This research demonstrates how the interplay of competitive and facilitative interactions affects food web dynamics and provides a novel modeling framework to study the dynamics of multiplex networks.