Nuclear gene sequences from a late pleistocene sloth coprolite.

The determination of nuclear DNA sequences from ancient remains would open many novel opportunities such as the resolution of phylogenies, the sexing of hominid and animal remains, and the characterization of genes involved in phenotypic traits. However, to date, single-copy nuclear DNA sequences from fossils have been determined only from bones and teeth of woolly mammoths preserved in the permafrost. Since the best preserved ancient nucleic acids tend to stem from cold environments, this has led to the assumption that nuclear DNA would be retrievable only from frozen remains. We have previously shown that Pleistocene coprolites stemming from the extinct Shasta sloth (Nothrotheriops shastensis, Megatheriidae) contain mitochondrial (mt) DNA from the animal that produced them as well as chloroplast (cp) DNA from the ingested plants. Recent attempts to resolve the phylogeny of two families of extinct sloths by using strictly mitochondrial DNA has been inconclusive. We have prepared DNA extracts from a ground sloth coprolite from Gypsum Cave, Nevada, and quantitated the number of mtDNA copies for three different fragment lengths by using real-time PCR. We amplified one multicopy and three single-copy nuclear gene fragments and used the concatenated sequence to resolve the phylogeny. These results show that ancient single-copy nuclear DNA can be recovered from warm, arid climates. Thus, nuclear DNA preservation is not restricted to cold climates.