Many plant populations exhibit substantial variation in demographic rates and dispersal. This intraspecific variation in demographic rates can arise from intra- and inter-annual variation in abiotic conditions or genetic differences among individuals which impact survivorship, growth and reproduction. Similarly, variation in dispersal rates can arise from intra- and inter-annual variation in environmental factor such as the magnitude and directionality of abiotic currents or the distribution and abundance of biotic dispersal agents. Alternatively, variation in dispersal rates may stem from genetic variation in dispersal related traits such as seed size or shape. When populations arrive in a new habitat, local demography and dispersal collectively determine whether the population persists and if it persists, the rate at which the population spatially spreads in this new habitat. Understanding this rate of spatial spread has and continues to play an important role in invasive, restoration, and conservation biology. In this talk, I will review, synthesize, and develop new theory about how intra- and inter-annual variability in demography and dispersal alter rates of spatial spread and to what extent the heritability of this variation plays an important role.
While non-heritable intra-annual variation in demographic rates have no effect on rates of spatial spread, non-heritable inter-annual variation slows down spatial spread, a finding consistent with expectations from classical stochastic demography. Heritability of this demographic variation can reverse this trend when different genotypes are adapted to different environmental conditions. Intra- or inter-annual variation in dispersal rates accelerate spatial spread. Variation in fecundity that is positively correlated with dispersal rates and heritability of these sources of variation strengthen this trend.