Tribe Calypsoeae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 113

Fig. 6.2 Bumblebee with pollinarium of Calypso bulbosa attached to the hairless area at the rear
of its dorsal thorax, scale bar = 5 mm. po pollinium, sc scutellum, vs viscidium
is more likely in some populations of variety a mericana in conjunction with the
higher frequency of clonal growth noted for this taxon (Mousley 1925 ; Mosquin
1970 ). Clonal growth is also common in the Eurasian variety bulbosa (Wollin 1975 ),
where Alexandersson and Agren ( 2000 ) reported high rates of self-pollination in
addition to important levels of pollen flow among populations.
Fruiting Success and Limiting Factors
The ability of the bee to recognize flowers of Calypso as unrewarding is reflected in
the levels of pollinator visitation. These levels can be estimated by the rates of pol-
linaria removal or displacement, pollinia deposition, and fruit set. Boyden ( 1982 )
found that only 101 (12%) of 843 examined flowers of variety americana in the