Species integrity and hybridization in anthropomorphic Orchis species (Orchidaceae).

Hybridization is widespread in Orchis (Orchidaceae), with 38 recorded hybrids between the 21 accepted species. The four anthropomorphic Orchis species that occur in Britain (O. anthropophora, O. militaris, O. purpurea and O. simia) are on the edge of their range and are of high conservation priority. Understanding how these species maintain their integrity in the face of hybridization is an important step in providing informed conservation management. This thesis examines hybridization between these four western European anthropomorphic Orchis species. To establish genetic structure in hybridizing populations a set of nuclear microsatellite markers were developed and the resolution of these markers was tested at the species level and the population level. The developed markers revealed new patterns of admixture in multiple O. militaris – O. purpurea, O. purpurea – O. simia and O. anthropophora – O. simia hybridizing populations in southern France. These patterns were reflected in labellum geometric morphometric data which correlated strongly with nuclear microsatellite data in all three species combinations. A DNA target capture and sequencing approach enabled the reconstruction of well-supported phylogenetic trees which placed an O. militaris – O. purpurea clade sister to O. simia. The evolutionary relationships were used to help make inferences about observed patterns of hybridization