Is there any definitive canon relating to various races of Elves, and how they treat each other or is it pretty much up to each individual author as to how various races/subraces of Elves get along?
Raymond Feist - Riftwar series - Several races of Elves, among them the glamredhel (mad elves), moredhel (dark elves), eledhel. They all mostly get along, and the eledhel actively try to break the power of the Dark Path to redeem their moredhel brethren.
Weis/Hickman - Dragonlance - Kaganesti, Sylvanesti, Qualanesti. Definite race striation, with the Kaganesti being seen as primitive and fit only for servants, with the Sylvanesti being the "highest" ranked race.
Tolkien - Falathrim, Sendar, Eldar - Various offshoots of the original 12/144 Elves (Tribes of Israel anyone?), generally all get along although they have some race wars (Wars of Beleriand) that can be attributed to the same reasons as human wars.
Given that Elves are one of the first "exotic" creatures and are a mainstay in fantasy fiction, is there an accepted reason for the variation in relationships among subraces or is that mainly an author preference to suit the flavor of the story being written at the time?