Project: Geography of Demography: modeling plant population responses to global habitat patterns
Funding: Marie Sklodowska-Curie Individual Fellowship
Timeframe: June 2015-June 2017
Host institution: Trinity College Dublin, Ireland
Mentor: Prof. Yvonne Buckley
Collaborators: Prof. Antoine Guisan and Dr. Olivier Broennimann, the Spatial Ecology Lab, University of Lausanne, Switzerland
Global environmental changes are causing enormous biodiversity loss, frequently referred to as the sixth mass extinction event on Earth. In this era of large-scale habitat rearrangements, ecologists need to derive global understanding of organismal responses to environmental conditions across large spatial extents. We need spatially explicit, mechanistic models of species’ persistence throughout the geographic area of distribution as well as global predictions of vulnerability to changing conditions. Over the last decades, ecologists have used correlative and process-based ecological niche models to explain the distributions of hundreds of species as a function of environmental variables. However, species distribution models do not take into account a key geographic feature known to severely alter population-environment interactions, the spatial configuration of suitable habitats. As a result, their usefulness in informing population and higher levels of ecological organization has remained weak and largely unexplored. Landscape features such as size of area occupied and large geographic barriers interact with life history, demography and organismal movement to modulate persistence patterns and as a result, forecasts of geographic distributions depend heavily on our ability to model how species interact with the landscape across large spatial extents. The project is addressing this fundamental gap in our understanding of the ecological processes defining species ranges by analysing the spatial structure of predicted distributions, with the aim of improving projections of species redistributions with global environmental changes.
With GEODEM we have used global species occurrence databases to construct species distribution models for over 800 plant species endemic to Europe. We have quantified the geographic range structure of these species using spatial tools and have used these results to test links between life history strategies of plants and the spatial configuration of suitable habitats. We have tested whether species' current range structure patterns (area occupied, connectivity between suitable habitat, habitat fractality etc.) can inform changes in geographic range structure in the future. With a finer approach, we then tested to what extent can the geographic position of populations within species' ranges inform on the suitability of the occupied habitat. Finally, we have modelled to what extent biological (species' niche properties, traits) and physical (continental barriers, geomorphological heterogeneity) factors might drive the revealed patterns. Our results demonstrate that continental-level analyses of geographic range structures are meaningful, though neglected tools in understanding mechanisms of species' distribution in space and time.
Expected potential impact
Current models of plant persistence have either ignored the effect of large-scale landscape patterns on organismal distribution and performance, or have tested population responses to theoretical models of range patterns, such as the “abundant centre” hypothesis (species are most abundant in the center of their range and decline in abundance toward the range edges). These tests have failed to detect meaningful spatial drivers of demographic variability, and this may be partly due to our ignorance of the spatial structure of habitats across geographic ranges and at range boundaries. The results of GEODEM are moving this field of Macroecology towards describing and quantifying the distribution of habitat suitability values derived from ecological niche modelling throughout a species range. We have developed predictive models of how these spatial patterns are linked to variation in life history traits and physical properties of the landscape over the species' geographic ranges. Such models have not been previously considered across large spatial scales, and no generalizations have been attempted across multiple species and life histories.
GEODEM has addressed fundamental theoretical concepts of Biogeography, advancing our mechanistic understanding of plant-environment interactions across large spatial scales. Our models will have important conservation applications in the future (e.g. measures of connectivity of populations, creation of migration corridors, identification of areas of potential species extinction and expansion, nature reserve design) and will potentially open up avenues for developing new theory in Macroecology and Biogeography research in the future.
- Csergő AM et al. The relative effect of geographic isolation: a test on mainland and island populations (in prep.)
- Csergő AM*, Broennimann O*, Petitpierre B*, and Buckley Y*, Guisan A*, The geography of habitat suitability (in prep.)
- Broennimann O*, Csergő AM*, and Guisan A*, Buckley YM*, Global patterns in species' geographic ranges: a spatial analysis of habitat distributions (in prep.)
- Csergő AM, Salguero-Gómez R, Broennimann O, Coutts SR, Guisan A, Angert AL, Welk E, Stott I, Enquist BJ, McGill B, Svenning JC, Violle C, and Buckley YM (2017) Less favorable climates constrain demographic strategies in plants Ecol. Lett. link
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