Q: what anti-virus software is recommended for the Mac?

None. There are no viruses that affect OS X in the wild. AV software on a Mac is a complete waste and will usually cause more problems than it could possibly solve.

Malware is a different animal entirely and would not be stopped by AV software.

Apple does not endorse any AV software, nor should you use any.

That's interesting I've never seen any Apple documentation recommending AV software. Can you point us these
Help topics?

The last paragraph of that page is obsolete. The "Products Guide" that it refers to doesn't even exist anymore.

Apple's general statements about malware protection are here and here, and here are its instructions for removing the most common types of ad-injection malware. Those statements don't mention any third-party "anti-virus" or "anti-malware" product.

Our apologies Ralph. In fact, it does still exist

Safety tips for handling email attachments and content downloaded from the Internet - Apple Support

And the link to "Products Guide" goes directly to MacApp Store.

I will bring this to the attention of Apple.