Biology Reference
In-Depth Information
Pollinators and Pollination Mechanisms
E. helleborine is pollinated by wasps (Fig. 3.5c ). These insects are visually oriented
and often attracted to brown, yellow-green, and dull red colors (Wiefelsputz 1970 ). In
addition, Brodmann et al. ( 2008 ) recently demonstrated that E. helleborine produces
compounds that mimic green-leaf volatiles, chemicals released when herbivores, such
as caterpillars, feed on leaves (mostly six-carbon aldehydes, alcohols, and acetates).
Caterpillars, such as those of Pieris rapae (L.) (cabbage white), are known prey of
social wasps, and E. helleborine evidently mimics green-leaf volatiles in order to
attract wasps for pollination.
Judd ( 1972 ) found wasps to be the exclusive floral visitors in southern Ontario.
Vespula arenaria (Fabricius) [= Dolichovespula arenaria (Fabricius)] (sandhills
hornet), V. consobrina (Saussure) (blackjacket), and V. vidua (Saussure) (ground
hornet) carried up to three pairs of pollinia attached to the hairs on their lower frons
and clypeus, indicating multiple visits. They were mostly female workers, although
some males were also observed. Voth ( 1982 ) reported that female wasp pollinators
in Europe were older workers that were no longer feeding larvae or seeking animal
prey. A fourth species, Polistes fuscatus (Fabricius) (paper wasp), visited the flow-
ers in Ontario but carried no pollinia (Judd 1972 ). In addition, Mousley ( 1927 )
reported two other wasps, Vespula germanica (Fabricus) (german yellow jacket)
and, to a lesser extent, V. maculata L. (black wasp, bald-faced hornet) as the most
common pollinators in Quebec, and Dowden (in Luer 1975 ) observed the common
yellowjacket, V. vulgaris (L.) as a pollinator in New England. Catling ( 1983 ),
Mantas ( 1993 ), and Light and MacConaill ( 1998 ) reported unspecified wasps as
pollinators in Montana, Ontario, and Quebec, respectively. Honeybees are frequent
visitors in New England, but their long proboscises often allow them to reach the
nectar without removing the pollinia. Wasps, on the other hand, have short probos-
cises and are forced to penetrate deeply into the flower to reach the nectar. As a
result, their heads almost always contact the pollinia.
Studies in the Old World indicate that the legitimate pollinators of outcrossing
Epipactis species are also predominantly wasps of the family Vespidae (e.g., Darwin
1862 ; Kunth 1898 -1905; Meeuse 1961 ; Judd 1972 ; Nilsson 1981a ; Richards 1982,
1986 ; Ehlers and Olesen 1997 ; Ehlers et al. 2002 ). However, it has already been
mentioned that syrphid flies are the principal pollinators of E. consimilis (= E. hel-
leborine subsp. helleborine ) in Israel and E. thunbergii in Japan (Ivri and Dafni
1977 ; Sugiura 1996 ). Although Kew's World Checklist of Monocotyledons lists
E. consimilis as a synonym of E. helleborine var. helleborine , details of its pollina-
tion, especially the role of the hinge mechanism as described by Ivri and Dafni
( 1977 ), differ from that reported elsewhere for E. helleborine . Other Old World spe-
cies are pollinated by various flies, beetles, bees, and other hymenoptera, including
ants (e.g., Darwin 1862 ; Nilsson 1978, 1981a ; Brantjes 1981 ; Richards 1986 ). Ants
also supplement syrphid flies as pollinators of E. thunbergii in Japan (Sugiura 1996 ;
Sugiura et al. 2006 ). Of particular interest, honeybees, the most important pollina-
tors of Epipactis species in the Netherlands based on their abundance and mobility,
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