FOOD-DEPENDENT AND DENSITY-DEPENDENT DISPERSAL - EVIDENCE FROM A SOILCOLLEMBOLAN

1. Dispersal in a fungivore species of Collembola, Onychiurus armatus, in a homogeneous soil was theoretically approached as a deterministic compartmental process, in which the movement of animals between discr ete patches could be described by a series of differential equations o r by the discrete geometric probability distribution, assuming a const ant probability to move from one patch to the next. 2. Experiments wer e designed for a release of collembolans in two types of soil in a phy sical arrangement of distinct patches represented by vials connected b y tubings to cover a distance of 40 cm. Dispersal distances of individ uals were determined, and theoretical and observed distributions compa red. 3. Dispersal rates, estimated from transfer rate constants, range d from 0.020 to 1.42 day-1, suggesting that an average O. armatus move d less than 10 cm day-1. The probability to leave a patch varied betwe en 0.10 and 0.50. 4. Dispersal was dependent on population density, so il type and length of fungal mycelium; it was almost twice as high at a high than at a low density (90 000 and 30 000 individuals m-2) in a mor soil and four times as high in a sandy compared with a mor soil. D ispersal rate decreased as the mycelial length increased, especially i n a sandy soil. 5. Collembolans in a feeding phase had a higher tenden cy to disperse than those that were moulting. 6. Enriching the soil pa tch at 40 cm distance from the release point with a favoured food item , the fungal species Mortierella isabellina, increased dispersal rate by more than four times in a mor soil, suggesting that fungal odour ca n attract collembolans from a large distance and enhance their rate of movement more than a three-fold increase of their population density does.