Geographic Variation in Festuca rubra L. Ploidy Levels and Systemic Fungal Endophyte Frequencies

SERDAR   DIRIHAN; MARJO HELANDER; HENRY VAÈRE; PEDRO E. GUNDEL; LUCAS A. GARIBALDI; J. GONZALO N. IRISARRI; IRMA SALONIEMI; KARI SAIKKONEN

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2016

1932-6203

Polyploidy and symbiotic EpichloeÈ fungal endophytes are common and heritable characteristicsthat can facilitate environmental range expansion in grasses. Here we examined geographicpatterns of polyploidy and the frequency of fungal endophyte colonized plants in 29Festuca rubra L. populations from eight geographic sites across latitudes from Spain tonorthernmost Finland and Greenland. Ploidy seemed to be positively and negatively correlatedwith latitude and productivity, respectively. However, the correlations were nonlinear;84% of the plants were hexaploids (2n = 6x = 42), and the positive correlation betweenploidy level and latitude is the result of only four populations skewing the data. In the southernmostend of the gradient 86% of the plants were tetraploids (2n = 4x = 28), whereas inthe northernmost end of the gradient one population had only octoploid plants (2n = 8x = 56).Endophytes were detected in 22 out of the 29 populations. Endophyte frequencies variedamong geographic sites, and populations and habitats within geographic sites irrespectiveof ploidy, latitude or productivity. The highest overall endophyte frequencies were found inthe southernmost end of the gradient, Spain, where 69% of plants harbored endophytes. Innorthern Finland, endophytes were detected in 30% of grasses but endophyte frequenciesvaried among populations from 0% to 75%, being higher in meadows compared to riverbanks.The endophytes were detected in 36%, 30% and 27% of the plants in Faroe Islands,Iceland and Switzerland, respectively. Practically all examined plants collected from southernFinland and Greenland were endophyte-free, whereas in other geographic sites endophytefrequencies were highly variable among populations. Common to all populations withhigh endophyte frequencies is heavy vertebrate grazing. We propose that the detectedendophyte frequencies and ploidy levels mirror past distribution history of F. rubra after thelast glaciation period, and local adaptations to past or prevailing selection forces such asvertebrate grazing.