From 18S ribosomal sequence data to evolution of morphology among the fungi.

From ribosomal DNA sequence data we can estimate ascomycete relationships, the time of divergence of major ascomycete lineages, and the history of morphological evolutionary change. Groups long accepted by mycologists such as the filamentous ascomycetes with fruiting bodies, (the plectomycetes and pyrenomycetes) are supported by 18S rDNA sequence data. After generating a phylogenetic tree showing relationships, the geological time of divergence of major fungal lineages may be estimated, inferring elapsed time using the calibrated percent substitutions between sequences. Determining the pathway of evolution of morphological characters is more difficult than inferring the relationships among these taxa. To establish the history of morphological evolution, we need accurate trees receiving strong support from our data set. We also need taxa with the intermediate characters to reveal the sequence of events in morphological evolution. Soon, however, we may be able to take a more direct approach to evolution of morphological characters, sequencing the genes that code for the character.

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