PeerJ Preprints is going to be closed, BTW. Nobody has so much as hinted at a reason; the official statement on PeerJ's blog just claims "the time has come", there's no way to leave comments on that post, and when I wrote an e-mail to ask, I didn't get any reaction.
I suspect it's because it was never all that popular. Despite the strong push from folks like the SVPOW guys, according to a Facebook convo on Nick Gardner's wall, PeerJ preprints were always a hard sell for prospective submitters. They might try funneling things towards BioRxiv or PaleorXiv in the future, especially now that there is a glut of options available to people wanting to go that route.