Intrinsic and extrinsic drivers of source–sink dynamics

• Published in: Ecology and evolution 2016-02, Vol.6 (4), p.892-904
• Main Authors: Heinrichs, Julie A., Lawler, Joshua J., Schumaker, Nathan H.
• Format: Article
• Language: English
• Subjects: Computer simulation; Demography Beyond the Population; Dispersal; Dispersion; Dynamics; Factorial design; Growth rate; Habitat quality; Habitats; individual‐based model; landscape pattern; Mathematical models; Metapopulations; Population (statistical); Population growth; Source-sink relationships; source‐sink dynamics; Statistical models; Stochasticity; Subpopulations
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.2029

Summary Many factors affect the presence and exchange of individuals among subpopulations and influence not only the emergence, but the strength of ensuing source–sink dynamics within metapopulations. Yet their relative contributions remain largely unexplored. To help identify the characteristics of empirical systems that are likely to exhibit strong versus weak source–sink dynamics and inform their differential management, we compared the relative roles of influential factors in strengthening source–sink dynamics. In a series of controlled experiments within a spatially explicit individual‐based model framework, we varied patch quality, patch size, the dispersion of high‐ and low‐quality patches, population growth rates, dispersal distances, and environmental stochasticity in a factorial design. We then recorded source–sink dynamics that emerged from the simulated habitat and population factors. Long‐term differences in births and deaths were quantified for sources and sinks in each system and used in a statistical model to rank the influences of key factors. Our results suggest that systems with species capable of rapid growth, occupying habitat patches with more disparate qualities, with interspersed higher‐ and lower‐quality habitats, and that experience relatively stable environments (i.e., fewer negative perturbations) are more likely to exhibit strong source–sink dynamics. Strong source–sink dynamics emerged under diverse combinations of factors, suggesting that simple inferences of process from pattern will likely be inadequate to predict and assess the strength of source–sink dynamics. Our results also suggest that it may be more difficult to detect and accurately measure source–sink dynamics in slow‐growing populations, highly variable environments, and where a subtle gradient of habitat quality exists. The conditions and mechanisms that give rise to source–sink dynamics are poorly understood. To better identify systems in need of careful data collection and management, we use a series of controlled experiments using novel simulation methods to examine factors that incite and drive ecological systems to exhibit strong source–sink dynamics. Our results suggest that systems with species capable of rapid growth, occupying habitat patches with more disparate qualities, with interspersed higher‐ and lower‐quality habitats, and in relatively stable environments (i.e., fewer negative perturbations), are more likely to exhibit strong source–sink dynamics