Tribe Neottieae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 72

Fig. 3.5 Epipactis helleborine . ( a ) Flower, front view, scale bar=3 mm; ( b ) column, slightly
oblique side view, scale bar = 1 mm; ( c ) wasp entering flower, scale bar = 3 mm; ( d ) polliniarum,
scale bar = 1 mm. an anther, po pollinia, ro rostellum-viscidium, sd staminodium, sg stigma, vs
viscidium
Compatibility and Breeding System
Although the flowers are self-compatible, Muller ( 1988 ) concluded that autogamy
is absent, and Ehlers et al. ( 2002 ) found no evidence for it in bagging experiments
conducted on 13 populations from 3 geographic regions along a latitudinal gradient
of about 1,000 km from northern to southern Sweden. Similarly, Talalaj and Brzosko
( 2008 ) found allogamy to predominate in a 5-year study of three populations from
NORTHERN0OLAND!UTOGAMYISUSUALLYPREVENTEDBYTHEPOSITIONINGOFTHELARGE
rostellum and stigma (Fig. 3.5b ) (Mousley 1927 ; Ehlers et al. 2002 ; Talalaj and
Brzosko 2008 ). In addition, insect visitation with removal of the pollinia often
occurs very quickly after the flowers open.
Although van der Cingle ( 2001 ) attributed reports of autogamy to taxonomic
confusion, namely, the misidentification of distinct, but closely related autogamous
taxa as E. helleborine s.s., other workers have reported that following elevation of
the anther cap, the pollinia sometimes pivot at their points of attachment on the
rostellum and fall onto the stigmatic surface (Martens 1926 ; Mousley 1927 ; Light
in Squirrell et al. 2001 ). Also, in older, unvisited flowers, the pollinia may expand
and become friable, and an elevated anther cap then allows pollen fragments to
break away, some reaching the stigma (Mousley 1927 ; Talalaj and Brzosko 2008 ).
Hagerup ( 1952 ) described a similar process in Denmark, where tetrads were