Some species of Eucalyptus I've heard need fire for their seeds to "activate"/germinate. They've also discovered a huge variety of Australian plants in valley's

Some species of Eucalyptus I've heard need fire for their seeds to "activate"/germinate. They've also discovered a huge variety of Australian plants in valley's where the fire never reaches (think the Wollemi Pine); where everywhere else is really just eucalyptus. If fire could eventually start in an area you pretty much just have eucalyptus bush everywhere and nothing else. My non-educated hypotheses is that eucalyptus was a very dangerous weed that uses fire to basically kill everything else around it. It managed to kill via fire every other native Australian plant in the bush expect with the exception of some safe sanctuary spots (close to water, deep valley's where moisture content is higher) many years ago. Some other plants have evolved against this and adapted to fire however (think Australian grass trees).