This lichen is pioneer in xerosere

The correct option is crustose lichen.

Step-by-Step Explanation:

1. Understanding Xerosere:
A xerosere is a plant succession that starts in an extremely dry habitat, such as a bare rock, wind-blown sand dune, or desert. Initially, these habitats lack soil and nutrients, and have very limited water-holding capacity.

2. Pioneer Species:
The first organisms to colonize a barren, uninhabited area are called pioneer species. In the case of a rocky xerosere, the pioneers must be able to withstand extreme temperature changes, direct sunlight, and severe dehydration.

3. Characteristics of Crustose Lichens:
Crustose lichens (such as Rhizocarpon, Lecidea, and Rinodina) are uniquely suited to be the pioneers of a xerosere because:
- They form a thin, crust-like structure that is tightly adhered to the rock surface, helping them resist wind and physical displacement.
- They can survive long periods of complete desiccation (drying out) and quickly resume metabolic activity when moisture becomes available.
- They secrete organic acids (such as carbonic acid) that chemically react with the rock surface, weathering it and breaking it down into fine mineral particles.

4. Preparation for Future Stages:
The accumulation of weathered rock particles, combined with the organic debris from decaying crustose lichens, forms a very thin layer of soil. This newly formed soil layer can retain a small amount of moisture, making the habitat suitable for the next successional stage (foliose lichens, followed by mosses and herbaceous plants).