A pattern-oriented simulation for forecasting species spread through time and space: a case study on an ecosystem engineer on the move

Abstract

Modelling the spread of introduced ecosystem engineers is a conservation priority due to their potential to cause irreversible ecosystem-level changes. While existing models predict potential distributions and spread capacities, new approaches that simulate the trajectory of a species' spread over time are needed. We developed novel simulations that predict spatial and temporal spread, capturing both continuous diffusion-dispersal and occasional long-distance leaps. We focused on the introduced population of superb lyrebird Menura novaehollandiae in Tasmania, Australia. Initially introduced as an insurance population, lyrebirds have become novel bioturbators, spreading across key natural areas and becoming ‘unwanted but challenging to eradicate'. Using multi-scale ecological data, our research 1) identified broad and fine-scale correlates of lyrebird occupation and 2) developed a spread simulation guided by a pattern-oriented framework. This occurrence-based modelling framework is useful when demographic data are scarce. We found that the cool, wet forests of western Tasmania with open understoreys offer well-connected habitats for lyrebird foraging and nesting. By 2023, lyrebirds had reached quasi-equilibrium within a core range in southern Tasmania and were expanding northwest, with the frontier reaching the western coast. Our model forecasts that by 2085, lyrebirds will have spread widely across suitable regions of western Tasmania. By pinpointing current and future areas of lyrebird occupation, we provide land managers with targeted locations for monitoring the effects of their expansion. Further, our area of applicability (AOA) analysis identified regions where environmental variables deviate from the training data, guiding future data collection to improve model certainty. Our findings offer an evidence-based approach for future monitoring and provide a framework for understanding the dynamics of other range-expanding species with invasive potential.