Tribe Pogonieae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 167

Chapter 9
Tribe Pogonieae
Abstract Isotria verticillata is a clonal orchid with a xenogamous-geitonogamous
breeding system. Autogamy and agamospermy are absent. Isotria medeoloides is
autogamous but not agamospermous. I. verticillata is pollinated by short-tongued,
wide-ranging, polylectic bees. Pollinator visitation may limit fruit production.
Cleistesiopsis bifaria is a clonal, pollen-limited orchid with a geitonogamous-xeno-
gamous breeding system, but selfing reduces the percentage of healthy embryos.
Autogamy is absent. Bumblebees and leaf-cutter bees are primary pollinators.
Anthers disperse pollen tetrads in successive doses of decreasing size. Flowers pol-
linated with small pollen doses fade more slowly and sometimes receive additional
pollen to increase their seed output. Flowers also provide a pollen reward.
Keywords Isotria s Cleistesiopsis s$IVERGENTBREEDINGSYSTEMSs0OLLENLOADPAR-
TITIONINGs3TRATEGIESOFDECEITANDREWARDs3HORTTONGUEDBEESs"UMBLEBEESs
Leaf-cutter bees
The tribe Pogonieae is represented by five disjunct genera found on three continents
(Pridgeon et al. 2003 ). Two, in addition to Pogonia , are present in our flora.
Isotria Rafinesque
Isotria , comprised of two species, is restricted to North America.