Dear Ashwani,

Polyploid evolution of ferns is a wonderfully exciting topic that was intensively studied around years 1960-1980, and onwards. Professor Gábor Vida (Hungary) studied the subject for decades and made several discovery for certain group of ferns. The professor has already retired, however, I would suggest you to contact him and asking him about the key literatures of the subject.

Best regards, Péter

A lot of DNA in bigger genomes, like the ferns, is “junk DNA” and doesn't actually code for anything useful. ... In fact, the reason that ferns can have so many chromosomes is that they are ancient enough to have accumulated so many chromosomes.

the chromosome number and env resistance over 400 million years Any clue ?

Humans on the other hand are more careful with no accumulating junk DNA and therefore have a smaller, more information-dense genome. In fact, the reason that ferns can have so many chromosomes is that they are ancient enough to have accumulated so many chromosomes.