Who is The fathertrees from Xenocide and what is their importance?

Fathertrees represent the third and final stage of pequenino existence and also provide leadership among the piggies. Only the most honored of the brothers (males in the second stage of existence) are granted a third life as a Fathertree. The fathertrees grow out of the corpses of the brothers during a special ritual, retain all their memories, and can live many hundreds of years, in a kind of small scale immortality. The fathertrees are able to communicate with each other through philotes, much in the same way the hive queen does with her workers. In fact, the fathertrees can even speak with the hive queen herself philotically (like telepathy) and will even be able to communicate between worlds once the pequeninos colonize other planets.