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Divergence in sink contributions to population persistence (journal article)
Citation:
Heinrichs, J., J. Lawler, N. Schumaker, C. Wilsey, AND D. Bender. Divergence in sink contributions to population persistence (journal article). CONSERVATION BIOLOGY. Blackwell Publishing, Malden, MA, , 10, (2015).
Impact/Purpose:
Agencies such as US Fish and Wildlife strive continuously to incorporate the best and most modern ecological and conservation research into species management and protection decisions that they promulgate. Of particular interest lately is research into source-sink dynamics, which has the potential to better inform the development of reserve strategies intended to help ensure species are stable and well-distributed. This research illustrates how source-sink theory can be used to improve species management, and where problems might arise if the theory is misapplied.
Description:
Population sinks present unique conservation challenges. The loss of individuals in sinks can compromise persistence; but conversely, sinks can improve viability by improving connectivity and facilitating the recolonization of vacant sources. To assess the contribution of sinks to regional population persistence of declining populations, we simulated source-sink dynamics for three very different endangered species: Black-capped vireos at Fort Hood, Texas (Vireo atricapilla), Ord’s kangaroo rats in Alberta (Dipodomys ordii), and Northern spotted owls in the Northwestern U.S. (Strix occidentalis caurina). We used empirical data from these case studies to parameterize spatially-explicit individual-based models. We then used the models to quantify population abundance and persistence with and without long-term sinks. Our results suggest that the contributions of sink habitats vary widely. Sinks can be detrimental, particularly when they function as ecological traps for declining populations with low inter-annual growth rates (e.g., Alberta’s Ord’s kangaroo rat), or benign in robust populations (e.g., black-capped vireos when cowbird parasitism is controlled). Sinks, including ecological traps, can also be crucial in delaying declines when there are few sources (e.g., in black-capped vireo populations with high nest-parasitism rates). The roles of sinks can also be nuanced, with sinks supporting larger, more variable populations that are subject to greater extinction risk (e.g., northern spotted owls). In each of our case studies, new context-dependent sinks emerged, underscoring the dynamic nature of sources and sinks and the need for frequent re-assessment. Our results imply that management actions based on assumptions that sink habitats are generally harmful or helpful risk undermining conservation efforts for declining populations.
