Invasive sub-Antarctic grasses respond to increasing temperatures at the expense of chilling tolerance

Abstract

Climate change and global warming has large effects on the performance and spatial distribution of plants and is considered one of the underlying causes for the spread of invasive species. Particularly vulnerable is the vegetation in cold environments where plants selected for tolerance traits have reduced phenotypic plasticity and capacity to respond to warming temperatures. In contrast, invasive species are phenotypically plastic and respond positively to climate change at the expense of stress tolerance. We investigate this trade-off in traits measuring the photosynthetic response to warming, chilling tolerance and specific leaf area (SLA. of a phylogenetically constrained group of Pooid grasses. We correlate this to the extent to which their ranges have expanded on a cold Sub-Antarctic Island in the southern ocean. The invasive species responded strongly to warming, increasing photosynthetic rates by up to two-fold, while non-invasive species did not respond. The response was associated with increased stomatal conductance and not to modifications of the photosynthetic metabolism. In contrast, electrolyte leakage, a measure of chilling sensitivity, was higher in invasive than non-invasive species, and SLA followed a similar pattern. All three traits scaled linearly with the rates of range expansion and demonstrate that on a historically cold island, unprecedented warming over the last 50 years has favoured grass species that can respond to warming at the detriment of those that cannot, and negated the advantage that chilling tolerance must have conferred in the past. This shows that cold ecosystems are particularly vulnerable to warming as species selection for stress tolerance has limited their responsiveness to environmental change, while introduced invasive have no such limitations. We show clear mechanistic evidence of the physiology that underpins these warming and chilling tolerance traits. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.