EST-SSRs as a resource for population genetic analyses

Simple-sequence repeats (SSRs) have increasingly become the marker of choice for population genetic analyses. Unfortunately, the development of traditional 'anonymous' SSRs from genomic DNA is costly and time-consuming. These problems are further compounded by a paucity of resources in taxa that lack clear economic importance. However, the advent of the genomics age has resulted in the production of vast amounts of publicly available DNA sequence data, including large collections of expressed sequence tags (ESTs) from a variety of different taxa. Recent research has revealed that ESTs are a potentially rich source of SSRs that reveal polymorphisms not only within the source taxon, but in related taxa, as well. In this paper, we review what is known about the transferability of EST-SSRs from one taxon to another with particular reference to the potential of these markers to facilitate population genetic studies. As an example of the utility of these resources, we then cross-reference existing EST databases against lists of rare, endangered and invasive plant species and conclude that half of all suitable EST databases could be exploited for the population genetic analysis of species of conservation concern. We then discuss the advantages and disadvantages of EST-SSRs in the context of population genetic applications.