PARENT SESSION
Oral Session #63: Invasive Species: Terrestrial.
Presiding: D. Larson
Wednesday, August 7. 1:00 PM to 4:45 PM. Graham Meeting Room, TCC.

An Allee effect may limit invasion by the plant pathogen Tilletia indica.

Garrett, Karen^*,1, Bowden, Robert¹, ¹ Kansas State University, Manhattan, KS

ABSTRACT- Tilletia indica depends on encounters between wind-dispersed secondary sporidia of different mating types for successful infection and reproduction. This life history characteristic results in destabilizing density-dependent reproduction at low population levels, or an Allee effect. Invasions by this fungus are of particular interest because many countries have trade restrictions against wheat imports from regions that have been invaded by T. indica. We estimated the Allee effect based on T. indica life history by calculating the probability of infection for different numbers of secondary sporidia. We also estimated the threshold population size below which populations of T. indica are predicted to decline rather than grow. An Allee effect is probably important for long distance transport of secondary sporidia, since their concentration will generally be greatly reduced at the frontier of the invasion. For new populations initiated by teliospores, an Allee effect will probably be important only when the environment is nonconducive enough that the number of secondary sporidia produced stays low. Deployment of partial resistance and use of fungicides will be useful if they push population levels from above to below the Allee threshold.

KEY WORDS: invasion, pathogen, demography, Allee