Human activity influences genetic dynamics of widespread invader

Study of invasive grass species in two closely located sub-Antarctic islands shows clear effect of human activity on genetic diversity and population structure

GBIF-mediated data resources used : 516,947 species occurrences
Poa annua
Poa annua L. observed in South Georgia and the South Sandwich Islands by Hugo Hulsberg (CC BY-NC 4.0)

Human activities can affect the spread and invasion of alien plant species, but distinguishing external factors from intrinsic population dynamics can be challenging and require comparisons of invasions in areas both with and without human presence.

This study identified an ideal model system in the sub-Antarctic region: two South African islands, Marion Island and Prince Edward Island, that share similar biotic and abiotic conditions as well as a common invader (Poa annua L.). While Marion is home to a research station with year-round operations, Prince Edward remains largely unvisited.

To better understand the degree of invasion, the authors modelled the ecological niches of P. annua on both islands using GBIF-mediated occurrences. After gathering samples from different populations on both islands, they analyzed variations in genomic size, genetic diversity and structure.

The niche models for both islands showed that nearly their entire landmasses were climatically suited for the turfgrass, even though current distributions were limited to the coastlines. On occupied Marion Island P. annua populations had high levels of genetic diversity and low levels of structure, while the opposite was the case for unoccupied Prince Edward.

These results combined suggest that continued human activity on Marion facilitated ongoing gene flow and diversification. To mitigate increased spread and abundance on Prince Edward, the study recommends minimizing human activity to limit further introductions and thus avoid increasing the genetic diversity of the island's P. annua population.

Mairal M, Chown SL, Shaw J, Chala D, Chau JH, Hui C, Kalwij JM, Münzbergová Z, Jansen van Vuuren B and Le Roux JJ (2021) Human activity strongly influences genetic dynamics of the most widespread invasive plant in the sub‐Antarctic. Molecular Ecology. Wiley 31(6): 1649–1665. Available at: