The evolution of orchids
THE ORCHIDACEAE are a diverse and widespread family of flowering plants, commonly known as the orchid family. They are are often colourful and fragrant. There are over 25,000 different species of orchids occurring in the natural, as well as 100,000 or more man-made varieties.
The number, variety and location of these beautiful plants are absolutely amazing. The origin, evolution and diversification of orchids have been a mystery for many years. Scientists have now managed to partly decipher the orchids’ genetic code to find out more about how these plants function and how they have managed to evolve to such a degree.
Plants, including the orchids, face stressful environmental challenges related to seasons, rainfall, drought, among others, on a continuous basis.
These conditions affect the metabolic activity in these plants which eventually may cause changes in their development and their ability to survive. Only those plants that have adapted sufficiently to meet the challenges will survive. These adjustments affect the plants at the molecular and genetic levels. These genotypic changes including mutations (changes in the genetic structure) eventually bring about phenotypic changes, alterations in the visual expression as seen in the plant. The results are new plants better suited to meet the environmental challenge.
Orchid adaptation to their environment may occur in different ways.
They may produce large quantities of pollen to improve the chances of pollination. The formation of pollinia, lumps of sticky pollen, prevents the loss of pollen grains as the pollen is being carried by the pollinator from one orchid to another. Flowers have also evolved ways to attach the pollinia.
Although orchids may in some cases be self-pollinating, they sometimes rely on specific insects or birds for pollination.
DEVELOPMENT OF AN AERIAL LIFESTYLE
This adaptation paved the way for the ability to live on trees. These plants are called epiphytes. By exposing their roots to the open air, some plants have developed a method called crassulacean acid metabolism that helps them to survive only on fog, rain and nutrients. This diversification greatly increased the ability to be aerial and to occupy niches in the mountains.
The development of seeds without endosperm has allowed orchids to use their energy in the production of thousands of very small and light seeds. This increases the ease of dispersal and increases the possibility of seeds germinating in distant places.
Orchids may use other plants and trees for support and to enhance their exposure to sunlight or shade as the needs may be, and to provide nutrients.
Some orchids depend on fingi growing inside the orchid’s roots to help the plant to absorb water and minerals. These relationships are called symbiotic, with the orchid producing some nutrients that allow the fungi to survive.
Most orchid species may be found in tropical environments, but others can be found in semi-desert or colder regions. They are are not found in frigid or extreme arid environments.
Orchids may be described as new- or old-world orchids. The majority of new-world orchid species are found in Mexico, Central America and South America, as well as the higher regions like the Andes.
Orchids are also found in East, West and Central Africa, as well as Asia.
Orchids are found in all colours and may vary in size and weight from milligrams to tons.
Some orchids are subterranean (living underground). Some grow on rocks (lithophytes) and some grow in the soil (terrestrial). Most orchids grow on other plants or on trees. Epiphytes are, however, not parasitic.
Orchidaceae display various morphological features and varying lifestyles. Due to their adaptability and evolution, they have been able to occupy almost every known habitat on Earth.