Fábio de Barros
Diversity of orchids
Orchids consist in a family of plants, scientifically called Orchidaceae. It is one of the largest families among the Phanerogam (plants that produce flowers), with about 25,000 natural species, in addition to a number of hybrids produced artificially by the man that should be on the verge of 30,000. Orchids can be found in all vegetated environments of our planet, although they are much more numerous in tropical regions, where predominantly epiphytic species.
The orchids are always herblike, but cover species which may have only a few millimeters in height, up to very large plants, with a few meters length. As for the growth way they can be terrestrial, epiphytes, rupiculous, saxicolas, humicolus or saprophytes. Their flowers are adapted to the pollination by different agents, including birds (hummingbirds) and insects of several orders and different sizes. The great morphologic variation of the orchids is intimately related to the capacity to explore different types of environments, and this two features result of a high evolution rate in the family. Probably, the evolution in the Orchidaceae family was ruled by adaptations increasingly specialized towards the insect pollination and to the epiphytism. Among the most conspicuous adaptations to the pollination by insects stands out the presence, in the flowers, of a lip, which is a differentiated petal, usually more colored and outstanding.
Concerning the adaptations to the epiphytism, stands out the common presence of a tumescent organ, denominated pseudobulb, which represents a reservoir of water and nutrients, and the occurrence of a special type of photosynthetic metabolism, known as CAM metabolism (abbreviation of Crassulacean Acid Metaboliam). Due to the different adaptations and different occupied atmospheres, many times the orchids are among the most representative families, in number of species, in any flower inventory held in tropical and subtropical areas, although they never constitute a very conspicuous element when thinking of the physiognomy of the vegetation. Indeed, several flower inventories held in Brazil consider orchids at least among the five families with the greatest number of species, often being the first, when considering areas covered by forest vegetation.
The diversity of the orchids can be analyzed so much under the point of view of the local floras as under the point of view of the family as a whole. In the first case, stands out the great amount of species in the environment. In the second case, draws attention the wide variety of forms displayed by the species of the family. In fact, although most of the people when talking about orchids have in mind a plant with big, colored flowers and with a characteristic shape with the presence of a colored lip, the shape of the orchid's flowers is breathtakingly varied. The same goes to the vegetative parts that are not behind in format variation.
There is a third way to face the diversity of the orchids, but in a much more specialized sphere: the variability among samples within and between populations of each species.
Certainly those three ways to face the diversity are strongly related. They all have to do with evolutionary adaptations present in the family and they represent, in a certain way, just different levels of coverage.
So, how could one notice each of them?
In the case of the multiplicity of shapes inside of the family, it is enough to visit an exhibition of orchids, or to browse a book about them to notice the immense number of different types of plants. In the case of the diversity inside of local floras, it is enough to consult and one of them to find the Orchidaceae family always among the most representative ones. In the case of the variability of certain species, among and within populations, the perception of the phenomenon might depend of much more sophisticated techniques then the simple visual observation, requiring methodologies of genetic or morphometrically evaluation of the individuals.