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The genus Ravenelia represents the third largest genus of rust fungi and parasitizes a great number of leguminous shrubs and trees, mainly in the subtropics and tropics. Molecular phylogenetic analyses of this genus using nc 28S rDNA and CO3 sequences are presented with a special focus on South African representatives of Ravenelia. Many of the specimens had been collected by us in recent years, mainly from acacia species of the genera Vachellia and Senegalia. Morphological characters were extensively studied using light microscopy and scanning electron microscopy. The analyses resolved several well-supported phylogenetic groups. By linking these groups to their morphology and life cycle characteristics, it was possible to interpret the outcomes in terms of their evolutionary ecology and biogeography. Several characters previously used to define subgeneric groups within Ravenelia were found to be misleading because of assumed convergent evolution. However, host associations, the ability to induce aecial galls as well as the development of two-layered probasidial cells emerged as useful criteria for inferring monophyletic groups. Six novel Ravenelia species were discovered and described. Furthermore, five species represent new reports for South Africa, species descriptions were emended for two taxa, and a new host report emerged for R. inornata. Keywords Pucciniales. Raveneliaceae. Ravenelia moloto sp. nov.. Ravenelia molopa sp. nov.. Ravenelia modjadji sp. nov. Ravenelia doidgeae sp. nov.. Ravenelia spinifera sp. nov.. Ravenelia dumeti sp. nov.. Phylogeny. Diversity study This article is part of the topical collection on Basidiomycote Mycology in honor of Franz Oberwinkler who passed away in March 2018

Trees in the genus Vachellia (previously Acacia) are commonly infected by the gall-inducing rusts Raveneliamacowaniana and R.evansii. Rust galls bearing aecial infections and relating uredinial and telial infections on the leaves of nine Vachellia species not previously recorded to be infected by Ravenelia spp. have recently been collected in South Africa. The rust fungi causing these infections were characterised using molecular phylogenetic analyses of DNA sequence data of the LSU and ITS rDNA regions as well as morphological examinations. The host range of R.macowaniana and R.evansii was thus re-assessed and extended from four to nine species and from one to three species, respectively. Application of Principal Component Analyses (PCA) of telial morphological characters provided evidence of an effect of the host species on the teliospore morphology in R.evansii, but only minor effects in R.macowaniana. A novel gall-inducing Ravenelia sp. closely related to R.macowaniana, was found on Vachelliaxanthophloea and it is described here as R.xanthophloeae.

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Trees in the genusVachellia(previouslyAcacia) are commonly infected by the gall-inducing rustsRaveneliamacowanianaandR.evansii. Rust galls bearing aecial infections and relating uredinial and telial infections on the leaves of nineVachelliaspecies not previously recorded to be infected byRaveneliaspp. have recently been collected in South Africa. The rust fungi causing these infections were characterised using molecular phylogenetic analyses of DNA sequence data of the LSU and ITS rDNA regions as well as morphological examinations. The host range ofR.macowanianaandR.evansiiwas thus re-assessed and extended from four to nine species and from one to three species, respectively. Application of Principal Component Analyses (PCA) of telial morphological characters provided evidence of an effect of the host species on the teliospore morphology inR.evansii, but only minor effects inR.macowaniana. A novel gall-inducingRaveneliasp. closely related toR.macowaniana, was found onVachelliaxanthophloeaand it is described here asR.xanthophloeae.