What we learned about I-Y5451 (Isles-C2) in 2018

I-P37 project member Ryan Casey wrote this summary of recent discoveries about I-Y5451. This is the haplogroup that is sometime nicknamed Isles-C2, it has several distinctive STR marker values, especially DYS392=12. This branch is especially typical of central-western Ireland (counties Roscommon, Galway, Mayo etc.), and it has a MRCA who lived 1150 years ago according to YFull's estimate.
https://www.yfull.com/tree/I-Y5451/

You can see some I-Y5451 people here (be sure to change the page size box at the top to 5000):
https://www.familytreedna.com/public/I2aHapGroup?iframe=ycolorized

Ryan's summary:

• 1/26/18: Y43901 is shared by two men and becomes the second known subclade of Y5451 after FGC14463.
• 2/5/18: FGC14458 separates from the Y5451 SNP block after it becomes known it’s upstream.
• 6/6/18: FGC14463 is known to have occurred before FGC14449 because a man does BY testing and is positive for the former and negative for the latter, FGC14449 appears to be the SNP that defines the Keaveney surname.
• 10/15/18: Y128131 and possible equivalent SNP Y129461 are shared between two men and becomes the third known subclade.
• 11/2/18: BY150381 and equivalent SNP Y45719 are shared between two men and becomes the fourth known subclade.
• 12/10/18: A subclade of BY150381 called BY186335 is discovered along with its 7 equivalent SNPs and is shared by two closely related men with a Spanish surname

Click here to find our most recent tree for I-Y3723 which includes I-Y5451