02338nas a2200241   4500008004100000245010500041210006900146300001200215490000700227520154000234653003501774653001301809653001501822653001901837653001401856653003101870653002501901653001801926100001601944700001601960700001501976856010501991       2008                        eng d00a Parallel floral adaptations to pollination by fungus gnats within the genus Mitella (Saxifragaceae)0 aParallel floral adaptations to pollination by fungus gnats withi  a560-5750 v463 aThe widespread pattern of parallel flower evolution as an adaptation for particular pollinator agents, known as "pollination syndromes", has long drawn attention from evolutionary biologists. Here, we report parallel evolution of saucer-shaped flowers and an associated unusual pollination system within the lineage Heucherina, a group of saxifragaceous genera. Field observations reveal that 18 of 28 plant species studied are pollinated almost exclusively by fungus gnats (Mycetophilidae). Among the 18 species with a fungus-gnat pollination system, 13 have characteristic saucer-shaped flowers and are pollinated mainly by several unspecialized mycetophilid genera with short mouthparts. We performed phylogenetic analyses using nucleotide sequences of external and internal transcribed spacers of nuclear ribosomal DNA and reconstructed ancestral floral morphologies with an establishment of the model of floral character evolution under a maximum-likelihood framework. Our analysis indicates that there is significant directionality in the evolutionary shifts of floral forms in the Heucherina. The inferred phylogeny further supports four origins of saucer-shaped flowers, which is shared among 14 species that are traditionally classified into the genus Mitella. In addition, our analysis indicates the extensive polyphyly of genus Mitella, as also suggested previously. The results suggest that the flower-visiting fungus gnats have caused convergent selection for the saucer-shaped flower repeatedly evolved within Heucherina.10aAncestral state reconstruction10aGnoriste10aHeucherina10aMycetophilidae10aMyiophily10aPollination specialization10aPollination syndrome10aSaxifragaceae1 aOkuyama, Y.1 aPellmyr, O.1 aKato, M, .  uhttp://www.online-keys.net/sciaroidea/add01/Okuyama_et_al_2008_parallel_floral_adaptions_mitella.pdf