Antarctica may be vulnerable to invasion by Poa annua from a range of populations around the globe

Abstract

Poa annua L. is the only plant species that successfully invaded Antarctica, despite its high isolation and extreme environmental conditions. Usually such success is attributed to the high phenotypic plasticity of the species or a specific pre-adapted population that started the invasion. The applied significance of our paper is connected with the dilemma: should the control/phytosanitary effort be aimed at a specific source population, or should the preventive measures remain general? We aimed to examine reasons for annual bluegrass invasion success and assess its dependence on the origin of the source population. The main research question is whether the species presents an invasion risk regardless of the population origin, or are some populations better pre-adapted to invasion in Antarctica. We conducted four ex situ common garden experiments with different sets of environmental conditions. The experiments focused on comparing traits and responses of plants to edaphic and climate conditions emulating both optimal conditions for the species and Antarctic summer conditions. Plants used in the research originated from populations from eight different places in the world, including the population from Powsin, Poland, which is described in the literature as the suspected source of the invasion. While individuals from different populations differed in response to optimal conditions, they exhibited a similar response to simulated Antarctic summer conditions, regardless of their source. This confirms the species' high phenotypic plasticity. No studied population seems especially maladapted to Antarctic invasion, and all populations performed better in less extreme, warmer conditions. Synthesis and applications. Poa annua is capable of Antarctic invasion regardless of the propagule source and may become even more dangerous under climate warming. Therefore, the protection of Antarctica may be even more difficult in the future, as the survival barrier will be less restrictive. Specific management implications include minimizing the pressure of P. annua propagules accidentally introduced into Antarctica from any source and immediately removing any emerging individuals. The broader implication is that invasions in harsh, low-resource environments follow a different path than under optimal conditions, extending the time in which management actions may be performed, but making the species more conspicuous.