Tribe Pogonieae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 174

Fresh capsule weight and mean seed weight in I. medeoloides did not differ among
the treatments of Vitt and Campbell's ( 1997 ) study, but overall seed weight was highly
correlated with capsule dimensions and with plant size. Larger plants had larger cap-
sules containing a greater seed bulk. In addition, Vitt et al. ( 1996 ), in a 10-year study
in Maine, found that a successful reproductive effort in 1 year was significantly cor-
related with a reduction in reproductive status the following year. Such a correlation
suggests the presence of resource limitation just as the difference in the percentage of
capsule production in artificially pollinated and open-pollinated plants of I. verticil-
lata suggests pollinator limitation (Table 9.2 ). On the other hand, Mehrhoff's ( 1989a )
demographic data provide no evidence for a high cost of reproduction in I. medeoloides .
He found that 75% of flowering plants in stable populations flowered the following
year, whereas only 24% of nonflowering plants did so. In declining but still reproduc-
tive populations, the numbers were 59% and 10%, respectively.
I. verticillata produced many more pollen grains and ovules per flower than I.
medeoloides , but the pollen to ovule ratios (P:O) for these species were 3.9:1 and
3.8:1, respectively, suggesting efficient breeding systems (Mehrhoff 1983 ). Cruden
( 1977 ) predicted lower P:O ratios for autogamous as compared to xenogamous spe-
cies, a not surprising expectation if it is assumed that relatively more pollen grains
need to be produced when their probability of reaching the stigma is less certain. The
P:O ratio for I. verticillata is exceptionally low for a xenogamous species. Mehrhoff
( 1983 ) noted that pollination in I. verticillata is a relatively rare event, and the low
P:O ratio of this orchid may reflect a heavy reliance on propagation by cloning.
Cleistesiopsis Pansarin and Barros
Cleistesiopsis includes two species, both restricted to North America (Pansarin and
Barros 2008 ). Formerly included in the genus Cleisteis , the designation of a new
genus is based on an analysis of both molecular and morphological characters (for
details, see Cameron and Case 1999 ; Cameron et al. 1999 ; Pansarin and Barros
2008 ; Pansarin et al. 2008 ).
Cleistesiopsis divaricata (L.) Pansarin and Barros
(Spreading Pogonia) and Cleistesiopsis bifaria (Fernald)
Pansarin and Barros (Smaller Spreading Pogonia)
Distribution and Habitat
C. bifaria is found in the Appalachian Mountains from northern Georgia to West
Virginia and on the Coastal Plain from North Carolina to Louisiana (Catling and
Gregg 1992 ). It occurs in pine savannas, open oak-pine woods, and meadows on
mountain ridges and grades. Recent molecular data imply that West Virginia and