I am not of this family at all, but I put "Dohnert" into the new LDS search engine Family Search Record Search to see what came up and found a child's birth (and unfortunately, death some days later) in 1868 in Berlin, Brandenburg, Germany. Mother's name was Emilie Dohnert. This is possibly your line. The new database (indexed records from microfilms) is at http://pilot.familysearch.org/recordsearch/start.html#p
Also in the International Genealogical Index, there are Dohnerts from the late 1700s in Germany and I saw one girl born 1653 in Thuringen. There are some from Lancaster Co., PA, USA, from the 1700s but the spelling is missing the "t" on the end. I'd say it's the same surname, since they did a lot of phonetic spelling back then.