Submitted to: Mycoscience
Publication Type: Proceedings
Publication Acceptance Date: January 20, 2006
Publication Date: June 1, 2006
Citation: Szabo, L.J. 2006. Deciphering species complexes: Puccinia andropogonis and Puccinia coronata, examples of differing modes of speciation. Mycoscience. 47:130-136. Technical Abstract: Puccinia andropogonis and P. coronata are both macrocyclic heteroecious rust fungi with telia hosts in the Poaceae. P. andropogonis has a narrow telial host range (Andropogon gerardii and Schizachyrium scoparis) but a broad aecial host range that includes six different families. In contrast, P. coronata has a broad telial host range that includes more than 15 genera and a narrow aecial host range (Rhamnus sp.). In order to better understand the phylogenetics of these two species, DNA sequence analysis of the nuclear rDNA region (ITS) was performed. Eighteen collections of P. andropogonis from both telial hosts and four aecial hosts (Penstemon sp., Comandra umbellate, Zanthoxylum americanaum, and Lupinus perennis) were analyzed. Phylogenetic analysis (Neighbor Joining and Parsamony) of aligned ITS sequence resulted in trees with four distinct clades which were well supported by bootstrap analysis. These four clades separated by aecial host (I, Penstemon; II, Comandra; III, Zanthoxylum; and IV, Lupinus). In addition, the samples from the telial hosts separated into different clades (Schizachyrium scoparis in clade I and Andropogon gerardii in clades II, III, and IV). These results indicate that P. andropogonis is a complex with at least four different species and that speciation has occurred primarily by radiation on new aecial hosts. Fifteen collections of P. coronata including seven telial hosts (Arrhenatherum elatius, Avena sativum, Bromus inermis, Calamgrostis canadensis, Elytrigia repens, Holcus mollis, and Lolium perenne) and two aecial hosts (Rhamnus alnifolia and R. catharticus) were analyzed. Phylogenetic analysis resulted in five distinct clades primarily based on telial host (I, Calamgrostis; II, Holcus; III, Arrhenatherum, Avena, Lolium; IV, Bromus; V, Eytrigia). These results indicate that P. coronata is a complex with at least five different species and that speciation has occurred primarily by radiation on to new telial hosts. P. andropogonis and P. coronata are both species complexes and show different means of speciation.