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

DIRIHAN, S.; HELANDER, M.; VARE, H. ; GUNDEL, P.E.; GARIBALDI, L.A.; IRISARRI, J.G.N.; SALONIEMI, I.; SAIKKONEN, K.

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2016 vol. 11 p. 1 - 16

1932-6203

Polyploidy and symbiotic EpichloeÈ fungal endophytes arecommon and heritable characteristics that can facilitate environmental rangeexpansion in grasses. Here we examined geographic patterns of polyploidy andthe frequency of fungal endophyte colonized plants in 29 Festuca rubra L. populations fromeight geographic sites across latitudes from Spain to northernmost Finland andGreenland. Ploidy seemed to be positively and negatively correlated withlatitude and productivity, respectively. However, the correlations werenonlinear; 84% of the plants were hexaploids (2n = 6x =42), and the positive correlation between ploidy level and latitude is theresult of only four populations skewing the data. In the southernmost end ofthe gradient 86% of the plants were tetraploids (2n = 4x = 28), whereas in thenorthernmost end of the gradient one population had only octoploid plants (2n =8x = 56). Endophytes were detected in 22 out of the 29 populations. Endophytefrequencies varied among geographic sites, and populations and habitats withingeographic sites irrespective of ploidy, latitude or productivity. The highestoverall endophyte frequencies were found in the southernmost end of the gradient,Spain, where 69% of plants harbored endophytes. In northern Finland, endophyteswere detected in 30% of grasses but endophyte frequencies varied amongpopulations from 0% to 75%, being higher in meadows compared to riverbanks. Theendophytes were detected in 36%, 30% and 27% of the plants in Faroe Islands, Icelandand Switzerland, respectively. Practically all examined plants collected fromsouthern Finland and Greenland were endophyte-free, whereas in other geographicsites endophyte frequencies were highly variable among populations. Common toall populations with high endophyte frequencies is heavy vertebrate grazing. Wepropose that the detected endophyte frequencies and ploidy levels mirror pastdistribution history of F. rubra after the last glaciationperiod, and local adaptations to past or prevailing selection forces such as vertebrategrazing.