MSc student Lucienne de Witte - NHN & Hortus Botanicus Leiden

How fundamental novelties or changes in body plans originate during evolution is still controversial among biologists. The Modern Synthesis, mainly based on population genetics, explains how gradual processes by natural selection can be responsible for micro- and even macro-evolution. Homeotic varieties, however, that are able to establish stable populations in a natural environment, so-called “hopeful monsters”, prove that a saltational mode of character change is a potential alternative mechanism for speciation. Homeosis is a result of changes in developmental genes and is a type of variation in which “something has been changed into the likeness of something else”. In the homeotic mutant Coelogyne leungiana (Orchidaceae), the second perianth whorl of the flower has changed organ identity compared to the wildtype C. fimbriata: petals and lip are sepal-like. This morphological change might be caused by a different expression of MADS-box B class genes involved in floral development. Gene expression in different perianth whorls is investigated using RT PCR. The same B gene lineages (PI- and AP3) are expected to be expressed in wildtype sepals of C. fimbriata and the sepaloid petals and labellum of C. leungiana.