Tribe Neottieae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 59

Fig. 3.2 ( a ) Listera convallarioides , flower, oblique view; ( b ) fungus gnat ( Mycetophila sp.) with
pollen mass of L. cordata attached to its head, scale bars = 1 mm. po pollen mass
The most commonly reported pollinators of L. cordata in the coastal redwood
forests of northern California were fungus gnats (Fig. 3.2b ) in the families
Mycetophylidae ( Mycetophila Meigen sp.) and Sciaridae ( Sciaria Meigen sp.)
(Ackerman and Mesler 1979 ; Mesler et al. 1980 ). Hapeman ( 1996 ) also reported
fungus gnats as pollinators in Door County, Wisconsin. These insects did not always
orient themselves properly with respect to the column and did not always contact
the trigger hairs of the rostellum or deposit pollinia on the stigma (Mesler et al.
1980 ). The probability of pollination per flower visit was low, but this was compen-
sated by an abundance of gnats and a large number of visits.
The flowers of L. cordata show no evident adaptation to a specific pollinator. The
nectar is well-exposed, and the pollination mechanism is simple and can probably
be operated by many small insects with short mouthparts. Members of other insect
groups reported carrying pollinia in northern California included hymenoptera in
families Ichneumonidae and Braconidae ( Microgaster Latreille sp.). Although
interaction with these insects was sporadic and accounted for less than 0.1% of the
flower visits, Ackerman and Mesler ( 1979 ) and Mesler et al. ( 1980 ) thought that the
dominant role of fungus gnats at their site might be a regional phenomenon related
to the local abundance of these insects and that the primary pollinator might differ
at other sites, where fungus gnats are less common (Ackerman and Mesler 1979 ).
Other pollinators have, in fact, been observed elsewhere. For example, Tipula sub-
nodicornis Zetterstedt (Tipulidae) and a species of Microgaster (Braconidae) were