A tale of two horses : origins and population genetics of two feral horse herds
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Domestic feral horses have been living on two United States barrier islands since earliest record, and their origins are speculative. Legend holds that horses surviving Spanish colonial shipwrecks in these areas may have swam ashore to found these herds; historic records show previous residents brought domestic horses to the islands, and the escaped or abandoned animals may have founded the populations. Managers must balance the value of these horses with the negative impacts they have on their island ecosystems, and both populations are being managed at a size below their carrying capacity. Small, isolated populations such as these are subject to declines in genetic diversity due to inbreeding and genetic drift. This study examines the current levels of genetic diversity in the feral horse populations on Assateague Island, Maryland, and Shackleford Banks, North Carolina. I find high levels of genetic variability in both populations, in agreement with levels previously found within domestic horse populations. I also use nuclear microsatellite loci and mitochondrial sequences from horses within these populations and horses from domestic breeds to examine the possible origins of the feral populations. Nuclear diversity inferred through microsatellite loci confirm that these populations have been isolated for many generations and indicate that these populations are more similar to one another than to any of the breeds examined. Mitochondrial sequence divergence indicates these populations were founded by horses with diverse lineages. The possible Spanish origin was not supported.
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