Species delimitation and population structure of Microbotryum saponariae on Saponaria species
Final Report Abstract
Even though fungal plant parasites have often a tremendous impact on economy and ecology the understanding of micro-evolutionary processes that led to the known tremendous species richness is still limited. In the genus Microbotryum (Pucciniomycotina) studies revealed host species to be the driving force for radiation leading to an almost one parasite per host pattern. In contrast, Microbotryum saponariae infects three different species of the host genus Saponaria and in studies with standard molecular markers no host specific clustering could be observed. Thus the basic hypothesis of this project was that the host jump of Microbotryum saponariae onto the host genus occurred recently and the speciation process is not completed. We sampled specimens of Microbotryum saponariae from all three host species. The major part of the samples was from the host plant Saponaria officinalis were 282 specimens out of 32 populations were sampled. The fungus was found on nine populations of the host plant S. pumila resulting in 85 samples and one population of an infected Saponaria ocymoides with 10 samples was available. The genome of one strain per host plant was sequenced with NGS methods. A low coverage sequencing approach was chosen resulting in an average coverage of 1,5x. Based on this genomic data twelve pairs of primers were developed amplifying various microsatellite regions. The availability of three different strains reduced the time and material needed to find polymorphic markers. All samples were analysed with a fluorescence based fragment length analyse. Additionally, 17 genetic regions containing a high number of single nucleotide polymorphisms (SNPs) were analysed. The result of both analyses, the microsatellite as well as the SNP analyse, revealed clear clusters within Microbotryum saponariae on population level. We could show that the driving force of the differentiation is the host plant species and not the geographic distribution of the host. Only when samples from Microbotryum from Saponaria officinalis were analysed alone a clustering due to the geographic distribution became visible. These clusters and the occurrence of private alleles within M. saponariae indicate partly interrupted gene flow between populations. Our data suggests that Microbotryum saponariae is in the middle of a speciation process on three different host plants and is therefore a perfect study organism to gain better understanding of this process. Additionally we designed primers amplifying polymorphic microsatellite regions for Microbotryum silenes-acaulis on the host plant Silene acaulis. This plant shows a circumpolar artic-alpine distribution and is commonly infected. With this primers population studies it will be possible to investigate the influence on such a wide distribution on the genetic diversity of a plant parasitic fungi. With the new molecular tools out of this project it will be possible to analyse the impact of different host species and the geographic distribution on the speciation and radiation processes of two different species of the genus Microbotryum. These data can give us deeper insights not only into micro-evolutionary processes but also into principle patterns in the evolution of plant parasitism.
Publications
- (2012) Leucosporidium drummii sp. nov. a new microbotryomycete isolated from soil in Germany. International Journal of Systematic and Evolutionary Microbiology 62: 728-734
Yurkov A, Schäfer AM, Begerow D
- (2013) Contrasting phylogenetic patterns of anther smuts (Pucciniomycotina: Microbotryum) reflect phylogenetic patterns of their caryophyllaceous hosts. Organisms Diversity & Evolution 13: 111-126
Kemler M, Martín M P, Telleria M T, Schäfer A M, Yurkov A, Begerow D
(See online at https://doi.org/10.1007/s13127-012-0115-1)
