Patterns of reproductive isolation in Sardinian orchids of the subtribe Orchidinae

Abstract Orchids are globally well known for their highly specialized mechanisms of pollination as a result of their complex biology. Based on natural selection, mutation and genetic drift, speciation occurs simultaneously in organisms linking them in complexes webs called ecosystems. Clarify what a species is, it is the first step to understand the biology of orchids and start protection actions especially in a fast changing world due to human impact such as habitats fragmentation and climate changes. I use the biological species concept (BSC) to investigate the presence and eventually the strength of mechanisms that limit the gene flow between close related taxa. Islands are considered natural laboratories due their unique evolutionary trends which have led to a flora whose biology remains, in many cases, unknown and controversial. The main outcomes of this thesis are: i) clarify the number of orchid species currently recorded in Sardinia and discuss the relevance of studying orchids on island conditions; ii) adopting the biological species concept, investigate zygotic barriers in two endemic close related Ophrys species and iii) discuss the zygotic barriers in the two most important functional groups of deception in mediterranean orchids.