My son tested with 23andMe. The haplogroup name result was I-Z58. It doesn't have a numeral 1 after the letter I. Is I1-Z58 the same as I-Z58?
Yes, I1-Z58 = I-Z58, the basic tree goes Hg-I > I1-M253 > DF29 > Z58 Branch
A pretty up-to-date Z58 Tree is available at YFull dot com
William Hartley