Reduced-representation sequencing can be an affordable alternative to WGR, especially where many individual samples are required, where the species of interest has a large reference genome, or when a reference genome is unavailable. Successful applications of reduced-representation sequencing (or other approaches that do not use whole genome sequence data, such as transcriptomics) have been particularly useful when reconstructing the evolutionary history of biological invasions (e.g. , Gibson, de Lourdes Torres, Brandvain, & Moyle, 2020; Schmidt et al., 2020). However, reduced-representation sequencing does not allow haplotype data to be used, (see Box 3), cannot identify structural variants (see Part 4), may not provide sufficient resolution to estimate the timing of recent biological invasions (Part 3), and provides limited resolution when detecting adaptation or introgression throughout the genome (Parts 4 and 5). In addition, library preparation can be more time-consuming (and therefore expensive) than WGS approaches. Figures in this box are adapted from Hahn (2019).