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Aim A surprising finding of genetic studies of Phragmites australis is that native populations, whether in Europe or North America, are characterized by lower genetic diversity than non-native populations. What is not clear is whether higher diversity within invasive stands results from disturbance facilitating sexual reproduction or whether individuals with higher diversity have greater invasion potential. Location Upper Midwest, United States, North America. Methods To answer this question, we investigated genetic structure of native and non-native P. australis stands at multiple spatial scales and under differing levels of anthropogenic disturbance. Our goals were to assess the influence of habitat disturbance on genetic structure and determine whether patterns differed in native versus non-native stands. We also screened for hybrid genotypes, which have not been reported from this region. Results When controlling for disturbance, native and non-native P. australis exhibited relatively similar within-site genetic diversity and degrees of clonal growth, suggesting that their spread is comparably reliant on clonal versus sexual dispersal. In all cases, discrete clumps of P. australis were composed of multiple, closely related genotypes, indicating seed heads as the key dispersal units. The genetic structure of P. australis stands did not differ with disturbance; however, only non-native P. australis was found in highly disturbed anthropogenic habitats. Native P. australis stands exhibited lower genetic diversity overall, lower sexual reproduction in less disturbed sites and greater isolation by distance and differentiation among sites, which is consistent with its longer residence time in this region. We found no evidence of hybrid genotypes, despite native and non-native stands sometimes co-occurring. Main conclusions Our results suggest that invasion by non-native P. australis is sporadic, associated with disturbance and involves closely related individuals, likely derived from a single seed head. The ability of the non-native lineage to exploit a variety of anthropogenic habitats helps to explain its invasiveness.

Aim Biogeographers have long known that plant species do not fully encompass their fundamental niche. Nonetheless, in practice, species distribution modelling assumes that plant distributions represent a reasonable approximation of their environmental tolerance. For ecological forecasting, projections of habitat loss due to climate change assume that many species will be unable to tolerate climate conditions outside of those found within their current distributional ranges. We aim to test how well occurrences in the native range approximate the climatic conditions in which plant species can survive. Location Continental USA. Methods We compared the climatic conditions between occurrences in the US native versus US non-native ranges using 144 non-invasive plant species. We quantified differences in January minimum temperature, July maximum temperature and annual precipitation as indicators of climatic tolerance. We also compared modelled potential distributions throughout the US based on native and total ranges to test how expanded climatic tolerance translates into predicted geographical range. Results Most species (86%) had non-native occurrences in climates outside those described by their native distributions. For the 80 species with lower minimum temperatures at non-native occurrences, the median expansion of minimum temperature tolerance was −2.9 °C. Similarly, for the 90 species with lower precipitation at non-native occurrences, the median expansion of minimum annual precipitation was −23 cm. Broader climatic conditions at non-native occurrences expanded the modelled potential geographical range by a median of 35%, with smaller range species showing larger expansions of potential geographical range. Main conclusions Our results show that plants' native ranges strongly underestimate climatic tolerance, leading species distribution models to underpredict potential range. The climatic tolerance of species with narrow native ranges appears most prone to underestimation. These findings suggest that many plants will be able to persist in situ with climate change for far longer than projected by species distribution models.

Aim Trophic cascades are a common consequence of herbivore outbreak and in the absence of hunting can cause the local extinction of native plant species and communities. We compared plant communities at 66 island and mainland sites to test the hypothesis that deer (Cervidae) determine species cover, richness and diversity and that palatable species become rare at high deer density. We validate a region-wide index of deer density and impact on plant communities in a region where culturally significant food plants maintained by aboriginal people prior to European contact helped to define baseline plant communities. Location Gulf and San Juan Island archipelagos and North American mainland. Methods We conducted surveys of 49 native, 10 exotic and 15 culturally significant plant species and deer sign at 66 sites on 35 islands and mainland to determine deer abundance and plant species cover, richness and diversity. We identified culturally significant food plants facilitated by aboriginal people using ethnobotanical knowledge, quantified plant palatability via cafeteria trials and characterized shrub architecture. Results Native and culturally significant shrub cover, richness and diversity were 52–85% lower at sites with abundant deer (0.9–2.8 ha−1) versus no deer. However, these values were also 38–82% lower at sites in the lowest deer density class (

Aim: Ecosystems face numerous well-documented threats from climate change. The well-being of people also is threatened by climate change, most prominently by reduced food security. Human adaptation to food scarcity, including shifting agricultural zones, will create new threats for natural ecosystems. We investigated how shifts in crop suitability because of climate change may overlap currently protected areas (PAs) and priority sites for PA expansion in South Africa. Predicting the locations of suitable climate conditions for crop growth will assist conservationists and decision-makers in planning for climate change. Location: South Africa. Methods: We modelled climatic suitability in 2055 for maize and wheat cultivation, two extensively planted, staple crops, and overlaid projected changes with PAs and PA expansion priorities. Results: Changes in winter climate could make an additional 2 million ha of land suitable for wheat cultivation, while changes in summer climate could expand maize suitability by up to 3.5 million ha. Conversely, 3 million ha of lands currently suitable for wheat production are predicted to become climatically unsuitable, along with 13 million ha for maize. At least 328 of 834 (39%) PAs are projected to be affected by altered wheat or maize suitability in their buffer zones. Main conclusions: Reduced crop suitability and food scarcity in subsistence areas may lead to the exploitation of PAs for food and fuel. However, if reduced crop suitability leads to agricultural abandonment, this may afford opportunities for ecological restoration. Expanded crop suitability in PA buffer zones could lead to additional isolation of PAs if portions of newly suitable land are converted to agriculture. These results suggest that altered crop suitability will be widespread throughout South Africa, including within and around lands identified as conservation priorities. Assessing how climate change will affect crop suitability near PAs is a first step towards proactively identifying potential conflicts between human adaptation and conservation planning.