Biology Reference
In-Depth Information
Chapter 8
Tribe Arethuseae (
Calopogon
R. Brown
and
Arethusa
L.) and Subfamily Vanilloideae
(Part One) (
Pogonia
Jussieu)
Abstract
Arethusa bulbosa
,
Calopogon tuberosus
, and
Pognia ophioglossoides
are self-compatible but adapted to outcrossing. The flowers produce little or no
reward and are probably pollinated primarily by deceit. Fruit production is pollen
limited. Pollinators are bees apparently attracted to the large, colorful perianths and
ultraviolet absorbing, anther-like brushes on the lips. Larger flowers of
C. tuberosus
discriminate among pollinators and prevent hybridization with three smaller,
sympatric species. Reproductive isolation among the smaller flowered taxa is main-
tained primarily by differences in phenology, habitat, and pollinator preference.
The flowers of
C. oklahomensis
are similar in size to those of
C. tuberosus
, but this
species is hexaploid and blooms earlier.
Keywords
Arethusa
s
Calopogon
s
Pogonia
s$ECEITPOLLINATIONs5LTRAVIOLET
ABSORBINGPSEUDOSTAMENSs2EPRODUCTIVEISOLATIONs0OLLENLIMITEDFRUITSETs#LUMP
ANDINmORESCENCESIZEEFFECTSs"UMBLEBEES
The tribe Arethuseae comprises 26 genera native to eastern Asia, New Guinea, the
southwest Pacific Islands, eastern North America, and the northern Caribbean
(Pridgeon et al.
2005
). Two genera,
Arethusa
and
Calopogon
, are found in our flora.
Arethusa
includes one species from North America and one from Japan while
Calopogon
, with five species, is restricted to North America. Most information on
its pollination biology is based on a single species.
Pogonia
, with one North American and three or four East Asian species, is also
considered here. It is assigned to subfamily Vanilloideae (see below) (Pridgeon
et al.
2003
) and is not closely related to
Calopogon
and
Arethusa
(e.g., Dressler
1981, 1993
; Freudenstein and Rasmussen
1997
; Cameron and Case
1999
; Goldman
et al.
2001
; Panasarin and Barros
2008
). However, the flowers of all three are simi-
lar in size and color (Luer
1975
), and the lip in each is similarly structured and
shares a cluster of stamen-like, yellow-white protuberances or brushes which
absorb ultraviolet light and are thought to function in the attraction and orientation
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