title: History and complexity in tick-host dynamics: discrepancies between 'real' and 'visible' tick populations.
abstract: BACKGROUND
  Numerical responses of ticks to changes in densities of their hosts can be complex and apparently unpredictable. Manipulations even of deterministic models can produce counter-intuitive results, including tick populations that either rise or fall under increasing host densities, depending on initial conditions.
  
  
  METHODS
  In this paper I use an established simulation model to demonstrate a wide range of numerical responses to different scenarios of host changes, and to examine the basic mechanisms that drive them.
  
  
  RESULTS
  The rate and direction of change of host densities affects the extent to which questing tick numbers reflect those of their hosts. Numerical responses differ profoundly between dynamic tick-host systems and those allowed to reach equilibrium.
  
  
  CONCLUSIONS
  The key to understanding tick-host dynamics is to understand the difference between 'real' and 'visible' tick populations. An appreciation of the implications of this difference - and of the conditions that influence it - will benefit the effective interpretation of field data.
authors.affiliation: School of Biological and Environmental Sciences, University of Stirling, Cottrell Building, Stirling FK9 4LA, UK. andrew.dobson@stir.ac.uk.
authors.forename: Andrew D M
authors.initials: AD
authors.lastname: Dobson
mesh_terms: D000818:Animals; D015415:Biomarkers; D003198:Computer Simulation; D006790:Host-Parasite Interactions; D011157:Population Dynamics; D013984:Tick Infestations / Q000453:epidemiology; D013987:Ticks / Q000502:physiology*; D013997:Time Factors
chemical_list: D015415:Biomarkers