Biology Reference
In-Depth Information
1988; van Heel, 1988; Vogel, 1998d; Smets et al., 2000; Rudall, 2002). Sep-
tal nectaries have been lost several times in monocot evolution, probably in
association with the development of different pollination systems (in aposta-
sioid orchids, some Tecophilaeaceae, some Xanthorrhoeaceae, some Aspara-
gaceae) or with the development of perigonal nectaries (in Liliales, some
Iridaceae, some Orchidaceae) (Daumann, 1970; Vogel, 1981a, 1998d; Dressler,
1990; Smets et al., 2000; Rudall, 2002). In addition, septal nectaries are
always absent in taxa with a gynostemium—a compound structure formed
by adnation of stamens and style (Rudall & Bateman, 2002).
Asparagales.
Septal nectaries are widespread in this order (Daumann, 1970;
Meerow, 1987; Vogel, 1998d; Smets et al., 2000; Rudall et al., 2003a; Gold-
blatt et al., 2004; Nepi et al., 2006; see Rudall, 2002, for a summary of their
positions). Even though in most families septal nectaries are always present,
in
Alliaceae
,
Asparagaceae
,
Asteliaceae
,
Blandfordiaceae
,
Boryaceae
,
Doryanthaceae
,
Iridaceae
,
Ixioliriaceae
,
Lanariaceae
,
Tecophilaeaceae
,
Xanthorrhoeaceae
, and
Xeronemataceae
they may be absent in some
members (Daumann, 1970; Rudall, 1998, 2002; Vogel, 1998d; Smets et al.,
2000; Rudall et al., 2003a). Rudall (2002) suggested that the loss of septal
nectaries has occurred
de novo
several times in this order, the absence of
nectar being related to alternative pollination modes, like buzz pollination in
some Asparagaceae, Tecophilaeaceae, Xanthorrhoeaceae, and apostasiod
orchids (Vogel, 1981a; Kocyan & Endress, 2001b; Rudall, 2002). In Irida-
ceae, when septal nectaries are absent, elaiophores, tepal, or staminal
nectaries can be found (Rudall et al., 2003a); these authors suggested that
perigonal nectaries may have evolved from septal nectaries by heterochrony,
i.e., developmentally later formation of nectaries in a more distal position on
organ primordia.
Septal nectaries are completely absent in the two monocot families Or-
chidaceae and Hypoxidaceae. In
Orchidaceae
, Smets et al. (2000) linked
this lack to the presence of unilocular ovaries in most species. As already
pointed out, orchids may have other floral rewards (pollen, perfume, oil) or
deceit pollination; there are also nectariferous flowers that have tepal nectar-
ies (Daumann, 1970; Nilsson et al., 1987; Dressler, 1990; Figueiredo & Pais,
1992; Galetto et al., 1997; Bustos Singer & Cocucci, 1999; Stpiczyńska et al.,
2005) and nectaries in the rachis or the pedicels of inflorescences (Fisher &
Zimmerman, 1988). On the other hand,
Hypoxidaceae
exclusively presents
pollen flowers, mainly with buzz pollination (Vogel, 1998d; Kocyan &
Endress, 2001a).
