Context: Traceability in Software Product Lines (SPL) is the ability to interrelate software engineering artifacts through required links to answer specific questions related to the families of products and underlying development processes. Despite the existence of studies to map out available evidence on traceability for single systems development, there is a lack of understanding on common strategies, activities, artifacts, and research gaps for SPL traceability. Objective: This paper analyzes 62 studies dating from 2001 to 2015 and discusses seven aspects of SPL traceability: main goals, strategies, application domains, research intensity, research challenges, rigor, and industrial relevance. In addition to the analysis, this paper also synthesizes the available evidence, identifies open issues and points out areas calling for further research. Method: To gather evidence, we defined a mapping study process adapted from existing guidelines. Driven by a set of research questions, this process comprises three major phases: planning, conducting, and documenting the review. Results: This work provides a structured understanding of SPL traceability, indicating areas for further research. The lack of evidence regarding the application of research methods indicates the need for more rigorous SPL traceability studies with better description of context, study design, and limitations. For practitioners, although most identified studies have low industrial relevance, a few of them have high relevance and thus could provide some decision making support for application of SPL traceability in practice. Conclusions: This work concludes that SPL traceability is maturing and pinpoints areas where further investigation should be performed. As future work, we intend to improve the comparison betWeen traceability proposals for SPL and single-system development. (C) 2016 Elsevier B.V. All rights reserved.