Herbarium specimens and the value of DNA in orchid classification and conservation
As dried plants can easily be used for DNA analyses, the 20'000 herbarium specimens of the Jany Renz collection could also be used for molecular research. As more and more orchids have been discovered and described since the 18th century, the task of producing artificial keys to various genera and higher taxa has become more complex, with the result that certain floral characters, which do not stand the weight of analysis today, were held up as hallmarks of certain genera. Excessive reliance on these characters has resulted in polyphyletic genera and total confusion about relationships at levels as low as the species and as high as the subfamily. The development of molecular technology and phylogenetic techniques in the last several decades has done nothing less than cause a revolution in biological classification. Not only are we able now to provide a genetic and more objective basis for analysis of generic concepts and relationships in the orchid family, but we can also reconstruct the evolutionary history of major groups within the family and trace its origins as well as better understand the evolutionary changes in vegetative and floral features of orchids.
Although morphological features, visible to the unaided eye or through a light microscope, are necessary for purposes of identification and still have a major role to play in orchid classification, DNA sequence data have several advantages. First, they allow us to determine whether morphological features in different organisms are related by common ancestry (homologous) or if they had independent origins. In other words, they show us, which morphological characters are good indicators of relationship and which are merely convergences as the result of similar selection pressures (pollinators, epiphytism, etc.). The result is a more useful, predictive, and accurate classification.
Second, sequences can be produced quickly and in abundance - hundreds, even thousands of characters at a time. Just as importantly, they can be easily communicated electronically, added to other databases including GenBank, and incorporated in analyses of related species around the world.
Third, DNA data have a predictive value. For example, if we learn that certain groups of plants have biochemical compounds with antibacterial or antiviral activity, then we can "harness" the genetic relationships uncovered to predict the possible occurrence of the same or similar compounds in groups of plants shown to be related by analysis of DNA sequences. From a horticultural standpoint, orchid hybridizers are able to use the information to predict whether two species can be successfully bred and, if so, what can be expected in the progeny.
Finally, at the levels of species and population, we are able to use DNA fingerprinting techniques to quantify genetic variation and use information on genotypes to resolve whether populations of a given species are genetically related and if they warrant special conservation status and protection. As a result, we can better determine conservation strategies for endangered or threatened species that are shown to be genetically and not just geographically isolated. With this information we can then focus limited management resources and funding more appropriately.
Given the implications of new molecular tools for systematics and conservation and the promise of still others in the next generation, ours is truly an exciting age, pioneering the next millennium for orchid enthusiasts everywhere.