Patchy Landscapes; Demography; Invasion; Spread; Arabidopsis thaliana; Dispersal
Lustenhouwer Nicky, Williams Jennifer L., Levine Jonathan M. (2018), Evolution during population spread affects plant performance in stressful environments, in Journal of Ecology
Williams Jennifer L., Levine Jonathan M. (2018), Experimental evidence that density dependence strongly influences plant invasions through fragmented landscapes, in Ecology
, 99(4), 876-884.
Lustenhouwer Nicky, Wilschut Rutger A., Williams Jennifer L., van der Putten Wim H., Levine Jonathan M. (2018), Rapid evolution of phenology during range expansion with recent climate change, in Global Change Biology
, 24(2), e534-e544.
Lustenhouwer Nicky, Moran Emily V., Levine Jonathan M. (2017), Trait correlations equalize spread velocity across plant life histories, in Global Ecology and Biogeography
, 26(12), 1398-1407.
Williams Jennifer L., Kendall Bruce E., Levine Jonathan M. (2016), Rapid evolution accelerates plant population spread in fragmented experimental landscapes, in SCIENCE
, (6298), 482-485.
Williams Jennifer L., Snyder Robin E., Levine Jonathan M. (2016), The Influence of Evolution on Population Spread through Patchy Landscapes, in AMERICAN NATURALIST
, (1), 15-26.
Two of the most pressing ecological concerns are the spread of biological invasions and species range shifts with climate change. At the heart of each dynamic is the advance of a population across the landscape. Predicting which introduced species will successfully invade, and which native species will shift their ranges requires a better understanding of spread. Theory predicts that in many cases, rare individuals at the invasion front make the propagules that advance the invasion, and that spread velocities tend to be constant. Nonetheless, our basic knowledge of spread is limited by two simplifications in most models. The first is a uniformly favorable environment; real landscapes are characterized by natural and anthropogenic barriers to spread. The second is the absence of evolution; selection on dispersal and growth can accelerate invasions. Importantly, recent work suggests that gaps between suitable habitat can cause high density individuals to drive population spread, altering selection on advancing individuals, and fundamentally changing how invasions advance. This proposal outlines experiments and models to explore (1) how landscape patchiness and density dependence interact to influence the spread of advancing populations, and (2) how landscape heterogeneity changes selection in advancing populations and the role of evolution in accelerating invasion velocities. To address these questions, we will integrate experimental invasions of the annual plant Arabidopsis thaliana with theoretical models of expanding populations. To test how landscape patchiness and density dependence regulate invasion velocities, we will compare the spread of replicate Arabidopsis populations over six generations on experimental “runways” in the greenhouse. We will vary landscape patchiness by changing the distance between the planting trays in the runways, and vary the strength of density dependence by changing the depth of the soil in the trays. To test the role of evolution in enhancing the invasion velocity, we will invade our landscapes with genetically variable Arabidopsis populations (multiple accessions and genotypes). We will prevent evolution in half of the replicates by replacing the individuals in each generation with the same seeds that began the invasion, thereby preventing changes to genotype frequency. Finally, we will explore how landscape patchiness affects the evolution of spreading populations by repeating our evolution manipulation, but with Arabidopsis populations invading runways with varying sized gaps between trays. All experimental work will be integrated into integro-difference equation models of population spread. We will use simulation and Evolutionarily Stable Strategy (ESS) analysis of these models to evaluate (1) the contribution of different types of density dependence to spread and (2) differing selection pressures in continuous versus patchy landscapes.Given the central place of population spread in our understanding of invasions, succession, disease, and range limits, understanding how landscape structure and evolution influence spread is important for advancing knowledge in ecology. Importantly, our work does so by bridging gaps between theoretical and empirical approaches. Finally, the work is important for a society concerned about biological invasions and the persistence of native species with climate change.