The role of dispersal limitation and reforestation in shaping the distributional shift of a forest herb under climate change

Aim: Forest herbs might be unable to track shifts in habitat suitability due to rapid climate change and habitat fragmentation. In this study, we quantified the role of dispersal limitation and the potential mitigating effect of large-scale reforestation on the redistribution of the herbaceous forest plant species Primula elatior under climate change.

Location: Europe

Methods: High resolution (100 m) landscape-scale and macro-climatic variables were combined to predict range-wide habitat suitability using Maxent. Dispersal limitation was modelled, based on isolation-by-resistance (IBR) principles through integration of circuit theory and genomic data, to assess patch accessibility and metapopulation stability under climate change. Large scale reforestation was evaluated as a potential mitigating strategy by incorporating a land-use change scenario into the distribution and dispersal models.

Results: Landscape-scale variables contributed significantly to the distribution of P. elatior (78.33%) and to the accuracy of our model (AUC=0.81). Isolation-by-resistance (R²cond=0.92) was driven by land-use (45.5%), distance from rivers (36.4%) and elevation (18.2%). It was estimated that 46.4±13.9% (mean±SD of climate change scenarios) of the total distribution area would be lost due to climate change by 2050 and an additional 15.6±1.7% (mean±SD) of the distribution would not be accessible through migration. The median latitude of the patch distribution shifted 183.2±34.8 km (mean±SD) northwards and 58.1±9.3 km (mean±SD) to more maritime regions. The patch accessibility was low in these regions and the metapopulation stability decreased considerably in the south of the distribution. Reforestation mitigated 54.1±18.2% (mean±SD) of the accessible distribution area loss and 49.5±4.2% (mean±SD) of the decrease in metapopulation stability.

Main conclusion: To alleviate the loss of the accessible distribution area of P. elatior under climate change, it will be required to integrate climate mitigation strategies (RCP 2.6), range-wide afforestation, restoration of ecological connectivity and focused assisted migration to newly available habitat.

Methods
Data collection and processing

Input_data_SDM.xlsx

Training and validation data (occurrences and pseudo-absences) used for the species distribution modelling. The data processing methodology can be found in section “Species occurrence data and pseudo-absence generation” of the manuscript. Coordinates of the occurrences were removed due to contractual obligations. The coordinates can be requested at the agencies listed in table I of Appendix S1 of the manuscript and an overview of the coordinates can be found in Fig. 1 of Appendix S1. The corresponding raster stack values (explanatory variables) of occurrences and pseudo-absences are integrated in this dataset.

PREDMEAN Raster tif files

The methods regarding the projections in space and time of the species distribution models can be found in the section “Model building and projections” of the manuscript. Further info on the input data preparation can be found in Appendix S1-SIII and more in depth evaluation of the models can be found in Appendix SVI-SV.

isolation_by_resistance.zip

Methods corresponding to the isolation by resistance relationship can be found in the section “Modelling dispersal and migration events to determine the accessible area” of the manuscript. Detailed methods about the genome sequencing can be found in Appendix SVII (genetic distance) and detailed methods about the effective resistances can be found in Appendix SVIII.

habitat_patch_shapefiles.zip

Methods in regard to the habitat patch delineation can be found in the “Model building and projections” section of the manuscript, methods regarding the dispersal and migration effective resistances and potential can be found in the “Modelling dispersal and migration events to determine the accessible area” section of the manuscript, and methods regarding the proximity resistance index can be found in the “Assessing shifts in patch distribution and configuration” section of the manuscript. A more in detail description of the genetic optimization procedure and resulting statistics of dispersal potential thresholds can be found in Appendix SVII.