WikiTree is one collaborative world tree we do not have individual trees as such, just some that have not been linked together yet. To find out if any people you are looking for are here yet use the Find menu, top right, People: Search.
William Bradford (Mayflower pilgrim) is profile-id Bradford-24.
http://www.wikitree.com/wiki/Bradford-24
Under the sources for this profile is: " Beem Genealogy, Publication: family tree done by professional genealogist Howard French in 1936 for Mrs. Berton Beem of Reading, Michigan. Note: This seems to be a private source." I worked on this profile, combining and merging all the information submitted to WikiTree for Gov. William Bradford. We porbably cannot separate out what came from any one source. There are profiles for Gov. Bradford's ancestors and descendants for a couple of generations. Most of those profiles were conbined and merged.