Abstract Detail

Poster Session

Wilson, Andrew [1], Bell, Charles [2], Aime, M. Catherine [3].

Deconstructing the co-evolutionary complexity of rust fungi (Pucciniales) and their plant hosts.

Rust fungi (Pucciniales) are simultaneously the most diverse and the most complex group of plant pathogenic fungi. The majority of Pucciniales require two specific but unrelated plant hosts in order to complete their life cycle. This life cycle can be distilled into two phases occurring on the different hosts, herein referred to as the aecial and the telial states/hosts. Previous attempts to look for evidence of co-evolution between the rust fungi and their hosts may have been complicated by the fact that there can be multiple hosts per species and that different selective pressures may be at work during different phases of the life cycle. Our working hypothesis is that the aecial host, which is the host on which sexual recombination in the form of fertilization occurs, is under the strongest pressure for conserving host associations, and therefore may retain the greatest signal of co-evolution. To test this hypothesis, we generated phylogenies for the Pucciniales and their hosts in order to compare aecial and telial host co-evolution ‘complexity’ separately. More co-evolutionary events indicate greater complexity in the co-evolutionary relationship between two organismal groups. These events can be counted using a parsimony-based approach implemented in the program Jane. Assessment of host-parasite phylogenetic congruence was performed at different taxonomic scales in the Pucciniales using three multi-gene datasets. For each set of analyses aecial and telial state host associations were compared and the state with the most parsimonious co-phylogenetic relationships is presumed to have been under greater selective pressure to retain associations as their hosts diversified. In addition we used molecular dating to correlate the diversification of major Pucciniales lineages with the diversification and evolution of their hosts. Molecular dating indicates that the Pucciniales emerged around 175 MY. This age pre-dates the earliest angiosperms, which arose around 160 MY. The majority of extant Pucciniales emerged around 117 MY as angiosperms were becoming widespread but gymnosperms remained dominant. This time also marks the divergence between the crown Pucciniales and the Melampsorineae, whose aecial state is associated with conifers. The Pucciniaceae arose and diversified around 50 MY, which is about 10-50 MY after the angiosperms became the dominant land plants, and around the same time that aecial and telial hosts in the Asteraceae (40-43 MY) and the Fabaceae (56-68 MY) are predicted to have appeared.

1 - Chicago Botanic Department, Plant Science and Conservation, 1000 Lake Cook Rd, Glencoe, IL, 60022
2 - University Of New Orleans, Department Of Biological Sciences, 2000 Lakeshore Drive, New Orleans, LA, 70148, USA
3 - Purdue University, Botany and Plant Pathology, 915 W. State Street, West Lafayette, IN, 47907, USA

Keywords:
Pucciniales
Rust fungi
Phylogenetic co-evolution
Molecular dating
fungal plant pathogen
host-pathogen co-diversification.

Presentation Type: Offered Paper - Poster
Session: P3
Location: Lincoln Room/Kellogg Hotel and Conference Center
Date: Monday, June 9th, 2014
Time: 8:00 PM
Number: P3007
Abstract ID:98
Candidate for Awards:None