A molecular analysis of ground sloth diet through the last glaciation

DNA was extracted from five coprolites, excavated in Gypsum Cave, Nevada an d radiocarbon dated to approximately 11 000, 20 000 and 28 500 years BF. Al l coprolites contained mitochondrial DNA sequences identical to a DNA seque nce determined from a bone of the extinct ground sloth Nothrotheriops shast ensis. A 157-bp fragment of the chloroplast gene for the large subunit of t he ribulosebisphosphate carboxylase (rbcL) was amplified from the boluses a nd several hundred clones were sequenced. In addition, the same DNA fragmen t was sequenced from 99 plant species that occur in the vicinity of Gypsum Cave today. When these were compared to the DNA sequences in GenBank, 69 we re correctly (two incorrectly) assigned to taxonomic orders. The plant sequ ences from the five coprolites as well as from one previously studied copro lite were compared to rbcL sequences in GenBank and the contemporary plant species. Thirteen families or orders of plants that formed part of the diet of the Shasta ground sloth could be identified, showing that the ground sl oth was feeding on trees as well as herbs and grasses. The plants in the bo luses further indicate that the climate 11000 years BP was dryer than 20 00 0 and 28 500 years BP. However, the sloths seem to have visited water sourc es more frequently at 11 000 BP than at earlier times.