The function of the wild carrot's dark central floret: attract, guide or deter?

Abstract

Although Charles Darwin wrote about flower polymorphism in the wild carrot, Daucus carota, the function of the conspicuous central dark floret is still unclear. We used video recordings to evaluate the functional significance of the dark central floret as a shortdistance signal for insects landing on the umbels and analyzed the location of landing points, landing orientation and visit duration. These parameters, as well as insect attraction did not differ on umbels with and without a dark central floret. Hence, we found no evidence for the role of the dark central floret in the pollination of D. carota. Umbels with a dark central floret, however, were parasitized significantly less often by the gall midge Kiefferia pericarpiicola than umbels without a dark central floret. We propose that the dark central floret may play a role in reducing parasite infestation by mimicking an already present gall or deterring oviposition of the gall midge by other means.

Attractiveness of the dark central floret in wild carrots: do umbel size and height matter?

“…Finally, we cannot refute the hypothesis that the DCF may mediate visitation by certain taxa, as we did not address this aspect in our study. Our conflicting results for umbels at different heights support the hypothesis that DCF function depends on ecological context, reliant on both the visitor community and the predominant flower phenotype (Goulson et al 2009;Polte & Reinhold 2013).…”

“…The function of the dark central florets (DCF), which not only vary in numbers but also in their presence within a population, has been a matter of debate for many years. Some authors have suggested that the DCF is a vestigial structure without a function (Darwin 1888), that it serves as a long or short distance signal to attract or deter flower visitors, or that it might function as a defense mechanism against herbivores, such as the gall midge Kiefferia pericarpiicola (Bremi) (Diptera: Cecidomyiidae) (e.g., Eisikowitch 1980;Lamborn & Ollerton 2000;Goulson et al 2009;Polte & Reinhold 2013).…”

“…Such a diversity of explanations attributed to the DCF appears to be a reflection of the generalized pollination system of D. carota, varying in function depending on the local pollinator availability and composition (Ollerton et al 2007;Goulson et al 2009;Polte & Reinhold 2013). For example, the number of floral visitors recorded for D. carota ranges from 20 species in Europe to more than 300 species in North America.…”

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

“…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). This issue needs further research to clarify the role of purple-colored flowers in Daucus species.…”

Exceptional evolutionary lability of flower‐like inflorescences (pseudanthia) in Apiaceae subfamily Apioideae

“…sphondylium (L.) are a plesiomorphic adaptation to flies and wasps in ancestral montane habitats. Moreover, many apioids with white petals and floral pseudocorollas (e.g., Daucus carota , Artedia squamata , and some species of Echinophora L.) develop so‐called “dark central florets”, which have been thought to attract certain species of coleopterans (Westmoreland and Muntan, 1996; Goulson et al, 2009) and flies (Eisikowitch, 1980) or facilitate pollinator's orientation during foraging (Polte and Reinhold, 2013).…”