Host visitation sequence as a determinant of search persistence in fruit parasitic tephritid flies

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Abstract
We tested, through field experiments and simulation models, the hypothesis that fruit-searching tephritid fruit flies adjust their within-tree search persistence according to the sequence and timing of encounters with parasitized (i.e. egg-infested) and unparasitized Crataegus sp. host fruit. In the field, we presented flies with 4 different sequences of unparasitized [=C] and parasitized [=M] fruit: 5M+0C; 1C+5M; 5M+1C, 1C+0M. Following fruit presentation, flies were permitted to forage freely within trees, which harboured no fruit, until emigration occurred. Under these conditions, flies that encountered the aforementioned different sequences of hosts, displayed differences in Giving Up Time, measured as active foraging time and number of leaf visits, in a manner predicted prior to testing. These differences were, however, not statistically significant. Based upon the results described above, we then built 3 simulation models that predicted within-tree Giving Up Times for individual flies: Model 1-Giving Up Time is incremented and decremented by fixed amounts following encounters by the fly with suitable (i.e. for oviposition) and unsuitable hosts, respectively; Model 2-similar to Model 1, but increment and decrement values are variable and are dependent upon the time since previous encounters by the fly with suitable and unsuitable hosts; Model 3-Giving Up Time is fixed. Comparison with previously reported field data for tephritid flies showed that Model 2 predicted rather well, and significantly better than Models 1 and 3, Giving Up Time for wild type tephritid flies under seminatural field conditions. We discuss our results in light of contemporary foraging theory.