Pre-dispersal predation of Taraxacum officinale (dandelion) seed

Authors


A. Honek (tel. +420 233 022269; fax +420 233 311591; e-mail honek@vurv.cz).

Summary

  • 1Pre-dispersal predation of seeds of Asteraceae has been studied in species where ripening seed is present on plants for long periods but rarely in those where seed maturation is ephemeral and density of consumers is therefore unlikely to keep pace with changes in seed availability.
  • 2We therefore followed predation of dandelion (Taraxacum officinale) seeds by the larvae of Glocianus punctiger and Olibrus bicolor and predicted that both abundance of seed consumers and seed damage will be indirectly proportional to inflorescence availability, and that overall seed damage will be less than in species with longer lived inflorescences.
  • 3We counted the number of dandelion capitula m−2, number of larvae capitulum−1 and percentage of damaged seeds at 10 sites, where the flowering time and densities of dandelions differed. The counts were made in 2002 and 2003, at half-weekly (April–May) or weekly (June–August) intervals.
  • 4Abundance of both species of consumer varied among dandelion patches, and with change in availability of dandelion capitula. Numbers of larvae capitulum−1 were high early and late, when few capitula were available, but decreased at the time of peak flowering when there were many capitula. Production of ready-to-pupate larvae m−2 of a species at a site was similar in successive years, but values for O. bicolor and G. punctiger were not correlated.
  • 5Seed damage paralleled the abundance of consumer larvae, with early and late flowers suffering most. A linear relationship correcting for lost seeds, predicted 30% damage when there were five larvae capitulum−1, below levels reported for species of Asteraceae with persistent inflorescences.
  • 6The intensity of pre-dispersal seed predation is directly proportional to the abundance of seed consumer species and indirectly proportional to the availability of maturing capitula. Consequently, in species with ephemeral, synchronized flowering, where seed is available for only a short time, the majority of plants lose only a small proportion to predators. Although those flowering earlier or later than the peak will suffer a much higher risk, the low overall level of damage is unlikely to influence population biology.

Ancillary