Multigene analysis suggests ecological speciation in the fungal pathogen Claviceps purpurea

Abstract

Claviceps purpurea is an important pathogen of grasses and source of novel chemical compounds. Three groups within this species (G1, G2, and G3) have been recognized based on habitat association, sclerotia and conidia morphology, and alkaloid production. These groups have further been supported by RAPD and AFLP markers, suggesting this species may be more accurately described as a species complex. However, all divergent ecotypes can coexist in sympatric populations with no obvious physical barriers to prevent gene flow. In this study, we used both phylogenetic and population genetic analyses to test for speciation within C. purpurea using DNA sequences from ITS, a RASlike locus, and a portion of beta-tubulin. The G1 types are significantly divergent from the G2/G3 types based on each of the three loci and the combined dataset, whereas the G2/G3 types are more integrated with one another. Although the G2 and G3 lineages have not diverged as much as the G1 lineage based on DNA sequence data, the use of three DNA loci does reliably separate the G2 and G3 lineages. However, the population genetic analyses strongly suggest little to no gene flow occurring between the different ecotypes and we argue that this process is driven by adaptations to ecological habitats; G1 isolates are associated with terrestrial grasses, G2 isolates are found in wet and shady environments, and G3 isolates are found in salt marsh habitats.

Ecological Genetic Divergence of the Fungal PathogenDidymella rabieion Sympatric Wild and DomesticatedCicerspp. (Chickpea)

“…Previous host specificity studies involved inter-and intraspecific hybridizations of fungal pathogens (15,36). However, despite the potential importance of ecological factors driving genetic divergence, they are poorly understood in fungi (18,22,32,33), and most of the existing data have been obtained from highly artificial experiments (18). In our work, the differences between the two parental isolates included both pathogenic fitness (RAUDPC and incubation period) and temperature adaptation.…”

Genetic diversity and recombination in natural populations of the nematode‐trapping fungus Arthrobotrys oligospora from China

“…), Claviceps purpurea (Douhan et al. ), Venturia inaequalis (Gladieux et al. ), fungal endophyte Colletotrichum gloeosporioides agg.…”

Comparison of Claviceps purpurea populations originated from experimental plots or fields of rye

“…Results obtained after crossing of two C. purpurea strains showed that single copy RAPD fragments segregate in a 1:1 ratio, and therefore can be used as genetic markers [18]. It was shown that data from RAPD as well as AFLP analyses were more informative than DNA sequences (i.e., β-tubuline gene or ITS rDNA) for separating the different ecotypes [38].…”