One of the novelties of wild bettas, is the ability to (with most species) house male and females together. Often the most difficult part of spawning domesticated B. splendens, is the actual introduction between the male and female. With wild bettas, you do not usually have to worry about this step because the pair share a tank and initiate spawning of their own accord.
This however, does not always mean a peaceful cohabitation. Indeed, I have found that aggression levels vary wildly based on the individual fish involved. Like nearly everything with these fish, there are no hard or fast rules.
Some of my pairs are quite tolerant of each other's presence and only spar during courtship. This includes my wild-caught burdigala pair, as well as my B. hendra pair. On the other hand, some of my males and females regularly rip into each other whether they intend on spawning or not. The worst offenders by far, are my captive bred B. burdigala pair.
Every single adult fish in that tank (three females and a male) have damage of some sort to their fins. The original female is extremely hostile towards the male at times, and this reaches a sort of violent climax right before they spawn. I long ago gave up on the hope that my male would ever fully grow back his fins. He is destined to go through life looking like a fighter from a Rocky Balboa film.
I have seen it mentioned that a lower temperature can lessen conspecific aggression, and I did seem to see less aggression from my B. brownorum pair when I brought the temperature down.
However, I have reached a far simpler conclusion.
Bettas are just jerks.
They are a feisty fish with an oversized attitude, and that is exactly why I keep them.
Hailing from Melbourne, Australia, I currently keep and breed a number of species from the coccina complex.