These are bots, most commonly plants, that continually reproduce. For non-plants this leads typically to a rapid population boom and equally rapid decline(graphs will show a sudden sharp spike). For plants this leads to an oscillating population size from extremely large to just a few. This is one of the most beneficial mutations for veggies since it allows them to immediately reproduce again, when the total veggie population size or total Energy is low enough to allow them to reproduce.
Since reproduction can't occur without enough space, a bot's death from over reproducing can be slowed if there is another plant or bot preventing continual reproduction.