Since its initial introduction to evolutionary biology, FCM has mostly been used to describe patterns of variation in ploidy within and among natural populations. Traditionally, these studies have been conducted by plant systematists interested in the taxonomic implications of chromosome number and have relied on conventional karyological techniques, which are technically challenging (especially with large chromosome numbers) and time-consuming (e.g. Stuessy et al. 2004). With FCM, ploidy variation can now be surveyed over large spatial scales and involve large sample sizes. For example, recent geographic studies routinely gathered DNA ploidy data from >1000 individuals (e.g. Baack 2004; Burton and Husband 1999; Husband and Sabara 2003). To this degree, FCM has revolutionized the field of cytogeography and is changing our perception of the magnitude of ploidy variation and its dynamic nature in the wild.
The extensive surveys of ploidy facilitated by FCM have fueled a number of research problems in population biology. Researchers have been able to more fully explore the distribution patterns and extent of ecological overlap between diploids and their polyploid derivatives. Specifically, FCM made it possible to better characterize regions of allopatry (Baack 2004; Ohi et al. 2003) as well as contact zones between multiple ploidies (Hardy et al. 2000; Husband and Schemske 1998; Liebenberg et al. 1993; Suda et al. 2004). These results have raised questions about the underlying historical and selective mechanisms maintaining these patterns (Felber-Girard et al. 1996; Johnson et al. 2003; Petit et al. 1999; Renno et al. 1995; van Dijk and Bakx-Schotman 1997). In addition to describing variation across entire geographic ranges, FCM has enabled researchers to map fine-scale distributions of ploidies within individual populations (Husband and Schemske 1998; Keeler et al. 1987 - the first article using FCM in field botany; Suda 2003; Weiss et al. 2002). This work is generally revealing greater cytotype variability and more hybrid cytotypes in natural populations than previously recognized.
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