Temporal origin of Chrysoporthe austroafricana and related species, estimated from ribosomal DNA sequences

• Published in: Journal of plant pathology Vol. 90; no. 3; p. 604
• Main Authors: van der Merwe, NA, Steenkamp, E T, Wingfield, B D, Wingfield, MJ
• Format: Journal Article
• Language: English
• Published: 01-11-2008
• Subjects: Myrtaceae
• ISSN: 1125-4653

Chrysoporthe austroafricana and Chrisoporthe cubensis (anamorph Chrysoporthella) are pathogens of woody Melastomat-aceae and Myrtaceae in tropical and subtropical regions of the world. C. cubensis is thought to have originated in South East Asia or South America, and recent discoveries of diverse populations of C. austroafricana on exotic and indigenous trees in South Africa indicate an African origin for this fungus. The distribution patterns of these fungi reflect possible continental origins. They are, however, associated with short terminal branches in all previous DNA based phylogenies, which suggests recent origins. In this study, we considered how long ago species of Chrysoporthe might have diverged from their ancestors. For this purpose, maximum likelihood analyses of the ITS region of the ribosomal DNA operon were used. Results show that Chrysoporthe emerged approximately three million years ago, which coincides with the end of the last ice age. The fungi in this assemblage are thus relatively young compared to species in the related genus Cryphonec-tria. The data also suggest that over-water dispersal most likely played an important role in the current distribution of these fungi, as their emergence estimate is well after the fragmentation of Gondwana. Thus, species of Chrysoporthe conceivably reached the areas where they are currently considered native at the end of the last ice age. They then entered a phase of rapid expansion and colonisation of new habitats as temperatures gradually rose, which is reflected in the diverse nature of their contemporary populations.