@ARTICLE{TreeBASE2Ref18182, author = {Doris Wolff and Sigrid Liede-Schumann}, title = {Evolution of flower morphology, pollen dimorphism, and nectar composition in Arcytophyllum, a distylous genus of Rubiaceae}, year = {2006}, keywords = {}, doi = {}, url = {}, pmid = {}, journal = {Organisms Diversity & Evolution}, volume = {}, number = {}, pages = {}, abstract = {A phylogenetic study of Arcytophyllum based on ITS was conducted and compared with an earlier study based on cpDNA. The position of the widespread A. thymifolium as sister to all other species was confirmed and several well-supported clades could be retrieved. The Central American A. lavarum is well embedded between exclusively or predominantly South American species. To understand the expression of heterostyly in the genus, we analyzed inter- and intraspecific variation in floral morphology, nectar, pollen-ovule-ratio and seed set of ten species in eleven populations. Stigma and anther levels differed significantly between the morphs in the species/populations investigated except for A. filiforme, in which anther levels differed not significantly between the two morphs. Different expressions of heterostyly in Arcytophyllum seem independent of phylogenetic relationships. Nectar sugar composition was similar between the morphs. Nectar of most species presented a larger proportion of hexoses than of sucrose, only the most derived species, A. macbridei and A. vernicosum, have higher sucrose proportions. There is a significant positive correlation between corolla tube length and the proportion of sucrose. Pollen dimorphism, both with regard to the number (long-styled > short-styled) and to the size (short-styled > long-styled) was observed in all taxa investigated except for A. filiforme. According to the pollen-ovule-ratios the breeding systems range from facultative autogamy to facultative xenogamy. The lowest P/O-ratios were found in A. filiforme the highest in A. rivetii. Hymenoptera, Diptera and Coleoptera were observed as flower visitors. Seed production did not differ significantly between the morphs in eight of the eleven species/populations investigated. There is, however a tendency in all species/populations (except for A. macbridei Peru) that the short-styled morph has a higher percentage of seeds per ovule indicating that the short-styled morphs display higher female reproductive success.} }

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