History of the trope
This trope was — at one time — a real scientific theory.
The Trope Maker was the 1947 paper "Expressions Studies on Wolves" by animal behaviorist Rudolph Schenkel, based on his work observing wolves at the Basel Zoo in Switzerland. It can be read here.
The Trope Codifier was wolf researcher L. David Mech, who popularized the idea by repeating it in his 1970 book — which he now considers an Old Shame.
The big turning point was switching from studying wolves in zoos to studying wolves in the wild.
Mech studied wild wolf packs on Ellesmere Island in Canada for 13 summers. Based on his observations there, he wrote a new paper in 1999, called "Alpha Status, Dominance, and Division of Labor in Wolf Packs." It can be read here.
You can see Mech talking about this concept here.
Wolves in the wild
A wolf pack typically consists of a breeding couple and their kids. Wolves look like adults by about a year old, but may not leave their parents quite so soon. Any other "adults" in a pack are usually older kids, between the ages of 1 and 3, who haven't left to form their own packs yet.
The parents have authority, not because of Asskicking Leads to Leadership, but because of Honor Thy Parent.
Calling the father wolf the "alpha male" or the mother wolf the "alpha female" is not strictly incorrect, but it's generally considered an inappropriate and misleading term these days because it falsely implies that the wolf hierarchy is based on force. Still, the term "alpha" is sometimes used to describe any dominant animal in a group, regardless of how it attained or maintains that status.
Wolves in captivity
Schenkel originally came up with the trope by observing wolves in a zoo. In that specific context, the trope is actually true.
Captive packs made up of unrelated wolves introduced to each other in adulthood tend to have a more volatile hierarchy. There's no natural order but physical strength. Disagreements must be settled, since they live in a smallish inclosure and the two parties can't simply part ways.
This very, very rarely occurs in the wild. Comparisons have been made to drawing conclusions about how human society works based solely on observation of people in prison.