Towards an interactive, process-based approach to understanding range shifts: developmental and environmental dependencies matter

Many species are undergoing distributional shifts in response to climate change. However, wide variability in range shifting rates has been observed across taxa, and even among closely-related species. Attempts to link climate-mediated range shifts to traits has often produced weak or conflicting results. Here we investigate interactive effects of developmental processes and environmental stress on the expression of traits relevant to range shifts. We use an individual-based modelling approach to assess how different developmental strategies affect range shift rates under a range of environmental conditions. We find that under stressful conditions, such as at the margins of the species? fundamental niche, investment in prolonged development leads to the greatest rates of range shifting, especially when longer time in development leads to improved fecundity and dispersal-related traits. However, under benign conditions, and when traits are less developmentally plastic, shorter development times are preferred for rapid range shifts, because higher generational frequency increases the number of individual dispersal events occurring over time. Our results suggest that the ability of a species to range shift depends not only on their dispersal and colonisation characteristics but also how these characteristics interact with developmental strategies. Benefits of any trait always depended on the environmental and developmental sensitivity of life history trait combinations, and the environmental conditions under which the range shift takes place. Without considering environmental and developmental sources of variation in the expression of traits relevant to range shifts, there is little hope of developing a general understanding of intrinsic drivers of range shift potential.