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:For example, most of the marine species that had been subdivided by lower sea levels around the Florida Peninsula still show a strong signal of regional structure, indicating that migration over long distances is insufficient to mix haplotype lineages among populations (Avise, 2000).
Category: