Table 1.
Environmental predictor variables pre-selected by expert knowledge.
| Category | Variables | Source | Reference |
|---|---|---|---|
| Climate data | Annual mean temperature, temperature seasonality, maximum temperature of warmest month, minimum temperature of coldest month, minimum temperature of May, mean temperature of wettest quarter, mean temperature of warmest quarter, annual precipitation, precipitation of driest month, precipitation seasonality, precipitation of wettest quarter, precipitation of driest quarter, precipitation of warmest quarter | Bioclimatic variables WorldClim1.4 – Global Climate Data of the current (reference period 1960–1990) climate conditions. Bioclimatic variables for future climate scenarios (CMIP5): NorESM1-M (RCP 4.5, RCP 8.5) MPI_ESM-LR (RCP 4.5, RCP 8.5) (Hijmans et al., 2005) |
Magnusson et al., 2008; Magnusson, 2010; Wasowicz et al., 2013 |
| Topography | Altitude | Bioclimatic variables WorldClim1.4 – Global Climate Data (Hijmans et al., 2005). |
Own consideration in accordance with Magnusson, 2010 |
| Aspect and slope | Manually calculated from altitude in R | ||
| Soil | Age of substrate | Icelandic Institute of Natural History (http://en.ni.is/). Accessed October 17, 2016. | Own consideration in accordance with Sigurdardottir, 2008; Magnusson, 2010 |
| Soil type | Agricultural University of Iceland (provided February 27, 2018) | Personal communication Dr. Olafur Arnalds; Arnalds, 2015 | |
| Land cover | Vegetation types: grassland and cultivated land, birch woodland, moss heathland | Icelandic Institute of Natural History (http://en.ni.is/). Accessed October 17, 2016. |
Hultén, 1968; Fremstad and Elven, 2008; |
| Surface water: rivers, waterbodies, glaciers | Magnusson, 2010 | ||
| Substrate: sand, lava, gravel plains | |||
| Human vector |
Distance to nearest road Human influence index (human population pressure; human land use and infrastructure; human access) |
Calculated based on the road map obtained from the NLSI: National Land Survey of Iceland (http://www.lmi.is/en/). Accessed January 04, 2017. Wildlife Conservation Society – WCS, and Center for International Earth Science Information Network – CIESIN – Columbia University, 2005. Last of the Wild Project, Version 2, 2005 (LWP-2). Palisades, NY: NASA SEDAC. doi: 10.7927/H4BP 00QC. Accessed January 04, 2017. |
Magnusson, 2010 |
Variables in bold were further selected by Pearson Correlation Coefficient, Jackknife and AIC and used to calibrate the species distribution model 1 (Maxent) of Lupinus nootkatensis. In model 2, we omitted the variable “distance to nearest road” but kept all other settings constant.