Horse microsatellites and their amenability to comparative equid genetics

We investigated the applicability of microsatellite primers, designed in horses, for use in plains and mountain zebras. Fifteen of the 20 tested horse-isolated primer pairs reliably amplified polymorphic loci in two wild equid species. We used this information to assess whether levels of genetic variation and repeat size differed in species from which microsatellites were isolated and in closely related target species. Target equid species exhibited similar levels of genetic variation to the horse, the species from which primers were originally isolated. We show that ascertainment bias results in lower mean and modal repeat size in target species. The data also provide evidence for a bi-directional mutational constraint in allele size across three equid species.