PARENT SESSION
Oral Session #9: Theoretical Ecology -- Populations, interactions.
Presiding: D. Srivastava
Monday, August 5. 8:00 AM to 11:30 AM. Grand Ballroom Central, Radisson.

Dispersal, demography, and invasion speed: Sensitivity and LTRE analysis.

Neubert, Michael^*,1, Lensink, Robert², Caswell, Hal¹, ¹ Woods Hole Oceanographic Institution, Woods Hole, MA² Catholic University of Nijmegen, Druten, The Netherlands

ABSTRACT- Rates of spread for invasive species can be calculated from information on demography (in the form of a stage-structured matrix population model) and dispersal (in the form of a distribution of dispersal distances). This invasion speed complements the use of population growth rate () as an index of population performance in conservation biology. We will present a new way to calculate the sensitivity and elasticity of invasion speed to changes in the order statistics of the dispersal distribution. This makes it possible to examine the effects of changing the distance dispersed by the longest-dispersing individual, the shortest, the median individual, etc. We apply the method to data on the Pied Flycatcher in the Netherlands, the Starling in the United States, and the Sparrowhawk in England and the Netherlands. We find that invasion speed is vastly more sensitive to changes in the upper percentiles of the dispersal distribution than to changes elsewhere. The sensitivity results make it possible to carry out LTRE calculations, quantifying the contribution of demography, short-distance dispersal, and long-distance dispersal to inter-population differences in invasion speed. Again, most of the dispersal effects are due to the upper percentiles of the dispersal distribution. The patterns revealed in the analysis of the four populations are very similar, suggesting that the dependence of invasion speed on long-distance dispersal may exhibit common patterns of sensitivity and elasticity.

KEY WORDS: long-distance dispersal, invasion rates, perturbation analyses, integrodifference equations