Supplementary Dataset for 'The “Trojan horse” strategy: seed fungal endophyte symbiosis helps to explain the invasion success of the grass Poa annua in Maritime Antarctica'

Supplementary tables 1-3 for the paper:<b>The “Trojan horse” strategy: seed fungal endophyte symbiosis helps to explain the invasion success of the grass </b><i><b>Poa annua</b></i><b> in Maritime Antarctica</b><b>Aim:</b><i>Poa annua </i>L. (annual bluegrass) is presently the sole invasive vascular plant species to have successfully established in Maritime Antarctica, where it poses a significant conservation threat to native plant species. However, the reasons for its success in the region have yet to be established. Here, we determined whether the invasiveness of <i>P. annua</i>, and its competitiveness with the native Antarctic hairgrass <i>Deschampsia antarctica</i>, is influenced by symbioses formed with seed fungal endophytes, and whether plants derived from seeds from four global regions differ in their performance.<b>Locations:</b>Four regions (Maritime Antarctica, sub-Antarctica, South America and Europe).<b>Methods:</b>Endophyte frequency was measured in<i>P. annua </i>seeds collected from the four regions. The germination, survival, biomass accumulation, flowering and competitiveness with <i>D. antarctica </i>of <i>P. annua </i>plants grown from endophyte-uncolonised and uncolonised seeds was determined in the laboratory. The effects of endophytes on <i>P. annua </i>seed germination and survival and seedling osmoprotection were also assessed in the Maritime Antarctic natural environment using locally-sourced seeds.<b>Results:</b>Endophytes were at least twice as frequent in seeds from Maritime Antarctica than in those from other regions. A higher proportion of endophyte-colonised seeds germinated and survived than did uncolonised seeds, but only when they originated from Maritime Antarctica.Seed endophytes increased the competitiveness of <i>P. annua </i>with <i>D. antarctica</i>, but only for plants grown from Maritime Antarctic seeds.In the field, endophyte-colonised seeds from Maritime Antarctica germinated and survived more frequently than uncolonised seeds, and osmoprotection was higher in seedlings grown from colonised seed.<b>Main conclusions:</b>The findings indicate beneficial effects of seed endophytes on invasion-related traits of <i>P. annua</i>, such as survival, germination success and flowering.Together with vegetative and reproductive traits facilitating the colonization process, the seed-fungal endophyte symbiosis can be invoked as an important factor explaining the invasiveness of <i>P. annua </i>in Maritime Antarctica.