For plants, which are sessile for most life history stages, seed dispersal is an essential process. Dispersal of seeds affects genetic diversity and species’ capacity for adaptation and the spread of populations. Aspects of dispersal ability may trade-off with other aspects of a life history strategy, such as reproduction. However, dispersal has not been incorporated explicitly into investigations of plant life history strategies. Quantifying the influence of dispersal on individual fitness and plant populations is challenging. Empirically, dispersal is difficult to observe, measure, and manipulate at the relevant scales needed to assess the full influence of dispersal. Analysis of spatial models with realistic assumptions about processes at multiple scales is a mathematical challenge.
We integrate disparate datasets of plant demography and dispersal to incorporate dispersal explicitly into plant life history strategies using analytical methods. We use the COMPADRE plant matrix database that currently has 637 species and 6242 matrices, and two dispersal datasets that we and colleagues have collated: 1) maximum dispersal distances for 576 species and 2) dispersal kernels for 168 species. We use these data to parameterize matrix population models and integro-difference equations to model population growth and spread, respectively, and examine trade-offs in plant life history strategies.
Recent findings analyzing life history strategies across species using the COMPADRE dataset have shown that life history strategies of plant species are explained by a major axis associated with growth and survival and another associated with reproductive strategies. To incorporate dispersal into life history strategies, we fit dispersal kernels across species. Variation in dispersal distances was best explained by plant growth form, dispersal mode, and plant height. Using the best-fitting mathematical description of dispersal kernels (the exponential power), we vary the distribution of dispersal distances across species based on plant growth form, dispersal mode, and plant height to predict population spread. Preliminary results indicate that dispersal ability shows important trade-offs with aspects of the life history and explains variation among species in the ability for populations to spread and invade new habitats. Incorporating dispersal into plant life history strategies and examining the ability of plants to spread will not only give us a better basic understanding of patterns of biodiversity and species distributions but also allow us to better predict species’ risk to climate change.