Elucidating the drivers of plant community dynamics on fragmented landscapes

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The long-term goal of my research program is to test key hypotheses concerning the drivers of short- and long-term changes in plant communities on anthropogenic landscapes. Over the next 5 years I will test the relative influence of dispersal ability, availability of suitable habitat, landscape context, and interactions between these factors in predicting whether or not a focal plant species of conservation concern is present in a local community. This work builds on my research over the past 5 years quantifying suitable habitat for rare plant species in the fragmented woodlands of southern Ontario using species distribution models (SDMs). My short-term objectives are: (1) To test whether measuring the amount of species-specific suitable habitat on the landscape surrounding a focal site can improve the ability of SDMs to predict species occupancy. Using geospatial analyses, my lab will test whether species-specific delineation of habitat improves our ability to predict the presence or absence of plant species of conservation concern based on habitat amount as a measure of connectivity. It has been shown that the role of habitat connectivity in predicting the presence or absence of bird species is more accurately estimated using species-specific delineation of habitat, but this approach has yet to be tested for plants. 2) To quantify the role of dispersal limitation and establishment limitation in the colonization of suitable habitat by plants. We will design and implement the first project to use SDMs for directing translocation of rare plant species. Planting trials will occur over a range of habitat suitability levels, including some sites currently already occupied by each species. We will also test the relative importance of dispersal ability and establishment by out-planting seeds, seedlings, and mature individuals. This research will provide a rare empirical test of SDM predictions, and help to fill the current gap in rare plant translocation research in Canada. 3) To estimate effective dispersal rates of pollen and seeds between isolated populations of rare plants on a fragmented landscape. We will use genetic analyses to test whether genetic differentiation between rare plant populations corresponds to geographic isolation of populations and/or contiguity of suitable habitat. We will quantify genetic diversity within and between populations of two species with contrasting life histories: the wood poppy and the crooked-stem aster. By examining genetic diversity within and between populations of these species we will determine how the severe fragmentation of southern Ontario forests is influencing genetic patterns. The proposed research will provide insight into fundamental ecological questions, such as whether niche limitation or dispersal limitation predominates in community assembly. The results will also inform future conservation planning and policy for plant species at risk in southern Ontario and elsewhere in Canada.