ferns grasses lichens mushrooms
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Over a long period of time, a rocky volcanic island that previously did not support any form of life got transformed into a dense forested region. Which of these species is most likely to have been the pioneer species that initiated this transformation?
Possibilities:
- ferns
- grasses
- lichens
- mushrooms

lichens