Functional significance of the dark central floret of Daucus carota (Apiaceae) L.; is it an insect mimic?

Abstract

In Daucus carota L. (Apiaceae) the florets comprising the central umbellet of inflorescences are usually pink or dark purple, presenting a marked contrast to the surrounding umbellets, which are generally white. The number of dark florets varies, and some inflorescences have no dark florets. It has been proposed that the dark florets function as an insect mimic, and in so doing serve to attract insects to the flower. In contrast, other authors, Darwin included, suggest that they are functionally redundant. The present study examined whether the dark florets attract insects, and also whether this effect can be replicated by replacing these florets with an insect. At the study site in Portugal the predominant insect visitor was the beetle Anthrenus verbasci L. (Dermestidae), which is similar in size and shape to the dark florets. Large inflorescences and those with more dark florets attracted more beetles than small inflorescences and those with fewer or no dark florets. Inflorescences with the dark florets removed attracted fewer beetles visitors compared with intact inflorescences. Inflorescences in which the dark florets were replaced with one or a cluster of five dead, freeze-killed A. verbasci attracted more beetles than inflorescences from which the dark florets had been removed. Replacement of the dark florets with a relatively large Meloid beetle resulted in the attraction of markedly fewer A. verbasci. We conclude that the dark florets can act as an insect attractant for some insect groups by acting as an insect mimic, and that they are adaptive, in contrast to the speculations of Darwin.

Integrated Molecular and Morphological Studies of the <I>Daucus guttatus</I> Complex (Apiaceae)

“…This may be a plausible explanation for the case of dark-colored pattern present in D. guttatus clades 1, 2, 4. Westmoreland and Muntan (1996), and Goulson et al (2009) favored the hypothesis that the dark flowers in umbels of Daucus significantly increase both insect attraction and fruit production. Conversely, Polte and Reinhold (2013) demonstrated that the dark central floret in wild Daucus has no role in pollination, but may play a role in reducing parasite infestation by the gall midge Kiefferia pericarpiicola (Bremi, 1847).…”

Higher longevity and fecundity of Chrysoperla carnea, a predator of olive pests, on some native flowering Mediterranean plants

“…In about 90 % of individuals, the florets of the central umbellet are pink or purple in color (Lamborn and Ollerton 2000), presenting a marked contrast to the surrounding umbellets, which are generally white. Goulson et al (2009) concluded from their studies that these dark central florets are adaptative and can function as an insect attractant for some insect groups by acting as an insect mimic. The composition of the nectar and/or pollen of D. carota can also play a role in their suitability for different groups of insects.…”

Indirect effects on mutualisms: parasitism of bumble bees and pollination service to plants

“…In 2007, we grew individuals of Trifolium pratense L. (Fabaceae) and Solanum carolinense L. (Solanaceae) from seed in the greenhouse (see Plate 1). Rudbeckia and Daucus have floral morphologies that are associated with more generalist pollination systems (Waser et al 1996, Goulson et al 2009, and a wide range of insect species visit them in the field, when compared to Solanum and Trifolium (S. Gillespie, personal observation). Solanum was not used in 2008, as plants either failed to germinate or flower that year.…”