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

Supplementary tables 1-3 for the paper: 

  

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

 

Although Poa annua L. (annual bluegrass) is presently the sole invasive vascular plant species to have successfully established in Maritime Antarctica, the reasons for its success in the region have yet to be established. Here, we determined whether the invasiveness of P. annua, and its competitiveness with the native Antarctic hairgrass Deschampsia antarctica, is influenced by symbioses formed with seed fungal endophytes, and whether plants derived from seeds from four global macro-regions differ in their performance (Maritime Antarctica, sub-Antarctica, South America and Europe)

Endophyte frequency was measured in P. annua seeds collected from the four macro-regions. The germination, survival, biomass accumulation, flower production and competitiveness with D. antarctica of P. annua plants grown from uncolonised and colonised seeds was determined in the laboratory. The effects of endophytes on P. annua seed germination and survival and seedling osmoprotection was also assessed in the Maritime Antarctic natural environment using locally-sourced seeds.

Endophytes were at least twice as frequent in seeds from Maritime Antarctica than in those from South America, Europe and sub-Antarctica. A higher proportion of endophyte-colonised seeds germinated and survived than did uncolonised seeds, but only when they originated from Maritime Antarctica. The presence of seed endophytes in P. annua increased the competitiveness of the species with D. antarctica, but only for P. annua 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.

The findings indicate beneficial effects of seed endophytes on invasion-related traits of P. annua, such as survival, germination success and flower production. 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 P. annua in Maritime Antarctica.