Biology Reference
In-Depth Information
as already noted the flowers of
S. magnicamporum
have a strong and distinctive
fragrance (Sheviak
1973, 1976, 1982
). Catling and Brown (
1983
) think that pollina-
tors in mixed populations of these species may very well respond to these differ-
ences. At the same time, a general similarity in floral morphology may serve to
attract and reinforce the behavior of pollen vectors as in
Goodyera
(Kallunki
1981
;
Catling and Brown
1983
).
Pollinators and Pollination Mechanisms
The primary pollinators of this genus are medium sized (ca. 9-mm long) to com-
paratively large (15-20-mm long), long-tongued bees, particularly species of
Bombus
and to lesser extent members of the Megachilidae (Tables
2.3-2.9
) (Darwin
1862
; Robertson
1893, 1929
; Ames
1921
; Godfery
1931, 1933
; Catling
1980b,
1983c
; Sheviak
1982
). Smaller halictine bees (species of
Lasioglossum
(
Dialictus
Robertson) and
Augochlorella
) are adapted to the pollination of
S. lucida
(Table
2.7
);
visits of these bees to other species are often erratic and associated with inefficient
pollen transfer (see below) (Catling
1980b, 1983c
). Among the few remaining tabu-
lated insects, the importance of the andrenid
Calliopsis andreniformis
as a pollina-
tor of
S. lacera
(Table
2.5
) remains to be determined. The same may be said of the
long-tongued bees of the genus
Anthophora
and the typhiid wasp,
Myzinum
, reported
as pollinators of
S. diluvialis
(Table
2.8
). Sipes and Tepedino (
1995
) only rarely
observed them bearing any pollinaria, and they have not been implicated in the pol-
lination of other species of
Spiranthes
(Catling
1983c
).
In most
Spiranthes
, the nectar glands (calli) secrete their nectar into the base of
the floral tube (Fig.
2.5a
) (Ames
1921
; Correll
1978
; Catling
1982, 1983c
). The
relatively long, curved galea and projecting tongue of
Bombus
species and
Megachilidae are well-adapted to reach this nectar source. The galea is hinged to the
Stipes and when extended it reaches well forward of the head. As the insect inserts
its head into the flower to obtain the nectar, it brings the dorsal surface of the flat-
topped galea into contact with the viscidium (Fig.
2.5b
) (Catling
1983c
). The vis-
cidium is elongated and rigid in all northeastern species of
Spiranthes
, except
S.
lucida
(Fig.
2.3
) (see below), and attaches readily to the stiff, flat-topped galea
(Fig.
2.5c
) (Catling
1980b, 1983c
; Catling and Catling
1991
). It is oriented parallel
to the long axis of the proboscis and adheres to the middle or proximal upper surface
in bees with a short galea and to the distal upper surface in bees with a long galea.
A similar mode of attachment was reported for
Bombus
pollinators of
S. romanzof-
fiana
and
S. diluvialis
(see below) in western North America (Tables
2.6
and
2.8
)
(Larson and Larson
1987
; Sipes and Tepedino
1995
) and
S. spiralis
in England
(Darwin
1862
; Godfery
1933
).
The flowers open first near the base of the spike, and blooming proceeds upward
in sequence (e.g., Darwin
1862
; Catling
1983c
; Sipes and Tepedino
1995
). Individual
flowers are protandrous. In newly opened flowers, the lip and column are close
together and the stigma hidden (Fig.
2.4a
). At this male stage, incoming pollinia
Search WWH ::
Custom Search