How great is the biological diversity of the mosses in Mexico and what uses are they put to in the country?

21/07/2021

Mosses are plants of wide world distribution, which usually live in humid places or near water. They are among the first organisms to colonize rocks because when they grow on them they modify their surface, forming a substrate in which other plants can take root. In Mexico, it is common to find them as carpets on the floor of humid forests, although they also grow on the branches and trunks of trees, on the roofs of buildings, on concrete walls, and even on sewers. Nevertheless, how great is the biological diversity of these Mexican mosses, what uses are they put to in the country, and how many species are in danger of extinction?

Among the plants, mosses belong to the bryophytes, which historically have been used, from the scientific point of view, as working material to carry out hybridization studies and experimental production of the first polyploids in plants (plants with duplicate sets of chromosomes). They have also been used to carry out studies on the dispersal of flora over long distances. Mosses preferentially absorb certain mineral elements found in the substrate. Chemical analysis for the detection of such elements in certain species of mosses is sometimes more reliable than analysis of the substrate itself. Many mosses are known to grow where copper or radioactive minerals are abundant.

In recent years, the potential of mosses has been valued from other points of view. They can be used as indicators of soil, air, and water pollution. In Mexico City, air quality evaluations have been made using the presence of epiphytic mosses as indicators because these plants are very sensitive to certain pollutants such as sulfur dioxide, ozone, and volatile fluorides. Their response to these substances is useful for diagnosing toxic levels in the environment. Species with a wide global distribution, as well as those that grow in various habitats, can be useful for assessing pollution in variable environments.

For many years they have been used in horticulture, where their beauty is appreciated as ornaments in gardens, terrariums and to simulate grass in the nativity scenes of Christmas arrangements. This is probably the greatest use of mosses in Mexico. However, they can also be mixed with soil to improve water retention, although certain mosses could create an environment of excessive humidity that suffocates the seeds and slows the regeneration of vegetation. They could be very useful in forest regeneration through seed germination.

In some parts of the world, mosses have been used as filling material for mattresses and pillows because of their softness and water absorption capacity. Because of these same characteristics and their antiseptic properties, they have been used as packaging material for clothing, fragile objects, fruits, and vegetables, as well as a substrate for transporting live plants. They are also an excellent insulating material for filling cracks in the walls of cabins in cold countries.

For a long time, the number of Mexican moss species was an enigma. However, there are about 960 species and varieties of mosses in the country. This number of species places Mexico in an important place in relation to the diversity of mosses in tropical countries.

The 16th-century Codex de la Cruz-Badiano, recently returned to Mexico by the Vatican, records the use of two types of mosses to relieve fever and headache. Other examples of the medicinal uses of mosses are found in the international bibliography in which mixtures of mosses with vegetable oils are mentioned to prepare ointments to relieve minor wounds, insect bites, burns, eczemas, etc. Mosses have also been used to make surgical dressings because they absorb and retain liquids. These soft, cool bandages are made more quickly and at a lower cost than cotton bandages. In China, with its long tradition in naturopathic medicine, about 40 species of bryophytes are considered medicinal, and some of them are included in treatments for kidney stones, cardiovascular diseases, nervous diseases, tonsillitis, bronchitis, cystitis, etc.

In other countries, research has been carried out on the active principles of mosses, and there are data on their antibiotic activity (antibacterial and antifungicidal). In the United States, for example, studies have been carried out to determine their antitumor activity and promising results have been obtained in some of the families studied. However, direct contact with other species may produce certain ailments, including dermatitis. In the field of pharmacology, many studies on mosses are still needed.

According to studies, there are 103 species of endemic mosses in Mexico, which constitutes 10,070 of the known moss flora. There is a list of 25 species of mosses that are considered to be protected. However, other species may be locally threatened by agricultural practices, forest destruction, or massive collection, as is the case of Campylopus, Thuidium, and Hypnum, which are indiscriminately collected at Christmas. Of these, the most affected populations are those found near urban centers. It is possible that other species that apparently are not threatened, live in fragile environments or in reduced areas and therefore also need protection. It is clear that to conserve species of bryophytes we must preserve their habitats.

Source: Biodiversitas (6), Mexico: CONABIO