I cannot find anything in pub 590 that affirms that RMDs must be taken separately from traditional and beneficiary IRA's. Can someone link to a source for that?
google is your friend ....searched for this
https://www.google.com/#hl=en&cp=33....,cf.osb&fp=2adfbbf777968faa&biw=1011&bih=670
from here:
Avoiding Mistakes In Required Minimum Distributions (RMD)
found this:
Combining RMDs Must Be Limited to the Same Type of Retirement Plan
If you have multiple retirement accounts, you are allowed to combine and withdraw the multiple RMDs from one retirement account; however, only RMDs from certain types of retirement plans can be combined. The following combinations are permitted:
If you have multiple Traditional IRAs, you may calculate each IRA's RMD, combine these RMDs, and withdraw the total amount from one Traditional IRA.
If you have multiple 403(b) accounts, you may calculate each 403(b)'s RMD, combine all these RMD amounts, and withdraw the total amount from one 403(b).
If you have multiple inherited/beneficiary IRAs from the same decedent, you may choose to combine life-expectancy distributions for those inherited IRAs and withdraw the total from one inherited IRA.
You may not combine the RMD amount for different types of retirement plans. The following are examples of combinations that are not allowed:
You may not combine the RMDs for multiple qualified plans. Each RMD must be withdrawn from the respective qualified plan.
You may not combine RMD amounts for different types of plans. For instance, an RMD amount for a 403(b) account may not be withdrawn from a Traditional IRA or vice versa, and the RMD for a 403(b) account may not be withdrawn from a qualified plan.
RMD amounts for inherited/beneficiary IRAs may not be withdrawn from Traditional IRAs that you own.
Example
Sam inherited an IRA from his Aunt Suzie. The RMD amount for the inherited IRA is $6,000. Sam has his own IRA that he funded himself with regular and rollover contributions, and this year the RMD amount for his own IRA is $10,000. Sam cannot combine the two RMD amounts and withdraw from only one. Each RMD must be withdrawn from its respective account.
If you have multiple inherited/beneficiary IRAs from different decedents, you may not combine distributions for those inherited IRAs.
Should you inadvertently combine RMD amounts for different types of retirement plans, an RMD shortfall will result for the retirement plan from which you withdrew no RMD. For instance, say the RMD for your qualified plan is $10,000 and the RMD for your Traditional IRA is $5,000. If you withdraw $15,000 from the Traditional IRA and make no withdrawal from the qualified plan account, you will not have satisfied the RMD for your qualified plan account and will owe the IRS an excise tax amount of $5,000 (50% of the shortfall).
Read more:
Avoiding Mistakes In Required Minimum Distributions (RMD)