Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Life history traits are an appropriate and important focus for the study of the ecological and evolutionary importance of polyploidy because (1) life history traits are often main determinants of fitness (e.g., Levy and Feldman 2002; Otto 2007; Ramsey 2011), and (2), ploidy level has the potential to influence life history traits in both positive and negative ways (e.
Category: