PARENT SESSION
Organized Oral Session 23: The use of spatially explicit data in ecological investigations
Organizer(s): K Conrad, J Holland, and L Rew
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 511 C, Level 5, Palais des congrès de Montréal

Spatial dynamics of Red-Legged Earth Mite in western Australia.

Smith, Robert^*,1, Read, Jon^{1, 2}, Ridsdill-Smith, James³, ¹ University of Leicester, Leicester, UK² University of Warwick, Coventry, UK³ CSIRO-Entomology, Perth, W. Australia

ABSTRACT- The Red-Legged Earth Mite or RLEM Halotydeus destructor is a destructive, introduced pest of pasture in Western Australia with a wide host range. RLEM populations peak during the cool, wet winters (up to 3 generations per annum) while mites aestivate as diapause eggs during the hot summer. We analysed several years of data collected in the 1950s and found evidence of both direct (within generation) and delayed (lag 2-3 generations) density dependence. Detailed, spatially-explicit counts of RLEM at 252 regularly spaced (20m) points allowed us to identify large-scale aggregations that moved across the 10 ha sampled landscape. The scale was so large (about 1ha) that these aggregations must be generated by demographic rather than behavioural effects and may represent travelling waves of high density. RLEM competes with a collembolan (Sminthurus viridis), for which we also have spatially-explicit counts, and both are predated by a Bdellid mite. We suggest that the spatial patterns are generated by predator-prey-competitor interactions between species with limited dispersal abilities.

Key words: Halotydeus destructor, aggregation, density-dependence, competition