Predicting distribution patterns and recent northward range shift of an invasive aquatic plant: Elodea canadensis in Europe

Abstract

Climate data and distribution data for the Canadian waterweed Elodea canadensis Michx. from North America, whole Europe and Finland were used to investigate the ability of bioclimatic envelope models to predict the distribution range and recent northward range shift of the species in Europe. Four diff erent main types of models were developed using the North American data, including either three 'baseline' climate variables (growing degrees days, temperature of the coldest month, water balance) or an extended set of seven climate variables, both averaged either over a 30 year time slice or a longer 90 year time slice. Ten diff erent random selections of pseudo-absences were generated from the North American data, on the basis of which ten separate generalized additive models (GAMs) were developed for each main model type. All the 40 developed GAMs were applied fi rst to North America and then transferred to whole Europe and Finland. All the models showed a statistically highly signifi cant accuracy in the three study areas. Although the diff erences among the four main model types were only minor, the two extended model types showed on average statistically better performance than the two baseline models based on Bayesian information criterion (BIC) values, the amount of deviance explained by the models, resubstitution validation and four-fold cross-validation in North America. Th ey also provided slightly more accurate predictions of climatically suitable area for Elodea canadensis in Finland both in 1961-1984 and 1985-2006. However, the projections from the individual extended models were more variable than projections from the baseline models. Th us model predictions based on a variety of predictor variables but only one selection of pseudo- Heikkinen et al. / BioRisk 2: 1-32 (2009) 2 absences may be subject to biases, and outputs from multiple models should be investigated to better account for uncertainties in modelling. Overall, our results suggest that more attention should be paid to the careful selection of predictor variables and the use of multiple pseudo-absence sets in the ecological niche modelling in order to increase the reliability of the projections of the range shifts of invasive species. RESEARCH ARTICLE A peer-reviewed open-access journal Biodiversity & Ecosystem Risk Assessment

Climate change and the future distributions of aquatic macrophytes across boreal catchments

“…Profound changes in biodiversity, species distributions and invasions by exotic species are expected in boreal regions over the next few decades in general, and aquatic ecosystems are similarly threatened by ecological alterations due to climate change (Wrona et al. , 2006; Heikkinen et al. , 2009; Heino et al.…”

“…Temperature‐related increased growth rates of aquatic vegetation will probably result in occupation of current niches to some extent, but additional niche space created by climate change‐promoted overgrowth is probably the primary cause for the expansion of emergent aquatic macrophytes. Communities of emergent aquatic macrophytes are typically driven by species‐sorting processes along environmental gradients, where heterogeneous environmental conditions, with associated niche differences and sufficient dispersal, determine species distributions (see also Cottenie, 2005; Heikkinen et al. , 2009).…”

“…Bioclimatic envelope modelling has been proven to be an efficient way to predict future distributions of species, although more attention should be paid to the selection of environmental variables (Beaumont et al. , 2007; Heikkinen et al. , 2009).…”

“…, 2009) where climate change is projected to be strong (IPCC, 2007). Very few modelling studies have examined climate change effects on aquatic ecosystems in northern high latitudes (however, see Heikkinen et al. , 2009), and there is thus a need to examine these systems using a number of different techniques.…”

Factors affecting the distribution patterns of aquatic macrophytes

“…Although temperature within the thermal tolerance promotes growth and reproduction in aquatic plants, decrease in water temperature may be one of the factors that are responsible for depth-related reductions in the seasonal growth of macrophytes (Barko et al 1986). It is believed that the temporal changes in distribution of certain species of macrophytes are mainly temperature-driven (Heikkinen et al 2009;Alahuhta 2011;Kors et al 2012). The variations that occur in the species composition and distribution of certain species of aquatic macrophytes, mostly submerged ones due to thermal changes, indicate that temperature is as important as light in influencing competitive interactions among coexisting species (Anderson 1969;Allen and Gorham 1973;Barko et al 1986).…”