The most likely first colonizers of a bare rock are

The most likely first colonizers of a bare rock are lichens. Lichens are a symbiotic relationship between a fungus and an alga or a cyanobacterium. They are well adapted to grow on bare rocks and can tolerate extreme temperatures, high radiation, and minimal nutrients. Lichens are capable of breaking down the rock surface through a process called chemical weathering. The acids produced by the lichen can dissolve minerals in the rock and create small crevices where organic matter can accumulate. These crevices provide a habitat for other organisms like mosses and ferns. Over time, as mosses and ferns establish themselves on the rock surface, they can trap more organic matter and create soil. This soil provides a better environment for larger plants like shrubs and trees to grow. In summary, lichens are the most likely first colonizers of a bare rock due to their ability to tolerate extreme conditions and break down the rock surface. As they create small crevices, other organisms like mosses and ferns can establish themselves, leading to the development of soil and the growth of larger plants.