Empirical evidence for source–sink populations: a review on occurrence, assessments and implications

Abstract

Assessing the role of local populations in a landscape context has become increasingly important in the fields of conservation biology and ecology. A growing number of studies attempt to determine the source-sink status of local populations. As the source-sink concept is commonly used for management decisions in nature conservation, accurate assessment approaches are crucial. Based on a systematic literature review of studies published between 2002 and 2013, we evaluated a priori predictions on methodological and biological factors that may influence the occurrence of source or sink populations. The review yielded 90 assessments from 73 publications that included qualitative and quantitative evidence for either source or sink population(s) for one or multiple species. Overall, sink populations tended to occur more often than source populations. Moreover, the occurrence of source or sink populations differed among taxonomic classes. Sinks were more often found than sources in mammals, while there was a non-significant trend for the opposite to be true for amphibians. Univariate and multivariate analyses showed that the occurrence of sources was positively related to connectivity of local populations. Our review furthermore highlights that more than 25 years after Pulliam's widely cited publication on 'sources, sinks, and population regulation', in-depth assessments of the source-sink status of populations based on combined consideration of demographic parameters such as fecundity, survival, emigration and immigration are still scarce. To increase our understanding of source-sink systems from ecological, evolutionary and conservation-related perspectives, we recommend that forthcoming studies on source-sink dynamics should pay more attention to the study design (i.e. connectivity of study populations) and that the assessment of the source-sink status of local populations is based on λ values calculated from demographic rates.

Source-Sink Dynamics: a Neglected Problem for Landscape-Scale Biodiversity Conservation in the Tropics

“…Echoing the findings of Furrer & Pasinelli [10], we also found notable taxonomic biases in study effort, with a predominance of studies on mammals in all climate zones, and birds in particular in temperate zones (Fig. S1).…”

“…The review also revealed evidence of a taxonomic bias towards mammals and birds in source-sink research, and the authors suggested that sources and sinks may be more commonplace in nature than studies suggest [10]. Here, we perform a further review to examine whether there are regional biases in research on source-sink dynamics.…”

“…Despite this, source-sink dynamics remain seldom quantified in applied conservation research [9,10]. Failure to identify sinks can lead to erroneous or perverse outcomes from conservation decision-making.…”

“…A recent review of source-sink research [10] found only 73 studies that provide quantitative evidence for source-sink patterns in nature, from a sample of studies published between 2002 and 2013. The review also revealed evidence of a taxonomic bias towards mammals and birds in source-sink research, and the authors suggested that sources and sinks may be more commonplace in nature than studies suggest [10].…”

Designing cost-effective capture-recapture surveys for improving the monitoring of survival in bird populations

“…Methods have been developed to account for the issue of detectability, 55 based on the measure of the observer-animal distance (Distance Sampling; Buckland et al 2001) or on multiple surveys (hierarchical modeling, Royle and Dorazio 2008). Still, population size being the result of a balance between survival, recruitment, emigration and immigration, inferring population status from counts, whatever detectability is accounted for or not, may impair the assignment of the demographic status of a population (source vs. sink; 60 Furrer andPasinelli 2016, Weegman et al 2016). Surveys that consist of capturing, marking with permanent tags, releasing and then recapturing wild animals (i.e.…”