Molecular phylogenetics of the sexually deceptive orchid genus Ophrys (Orchidaceae) based on nuclear and chloroplast DNA sequences

We present a phylogenetic analysis of the major lineages of the sexually de ceptive orchid genus Ophrys based on nuclear ribosomal (nr) DNA (internal t ranscribed spacer region) and noncoding chloroplast (cp) DNA (trnL-trnF reg ion) sequences. Sequence divergence within and among major Ophrys lineages was low for both nrDNA and cpDNA sequences. Separate analyses resulted in s imilar but poorly resolved trees. An incongruence length difference test re vealed that nrDNA and cpDNA data sets were not incongruent, A combined anal ysis resulted in a better-resolved phylogenetic hypothesis of relationships among the major Ophrys lineages. Our data strongly support a division of O phrys into two groups. These groups do not correspond to the earlier propos ed sections Euophrys and Pseudophrys and are thus in conflict with traditio nal classifications. Our results support a well-resolved monophyletic group that contains the geographically widespread O. bombyliflora, O. speculum, O. tenthredinifera, and the O. fusca-lutea lineage. Relationships in the ot her group are poorly resolved. Based on our observations that tars with ide ntical sequences at presumably rapidly evolving loci clearly differ in flor al morphology, we hypothesize that the diversity in the genus Ophrys is the result of a recent radiation in this orchid lineage. (C) 2001 Academic Pre ss.