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characters in systematic treatments and sound phylogenies can clarify the
origin of reproductive characters or syndromes (Anderson et al., 2002).
Fortunately, several authors have demonstrated the taxonomic and evolu-
tionary value of floral nectaries in understanding the classification of many
angiosperm groups. Examples of the groups that have been analysed with
interesting and challenging results are: Apocynaceae-Asclepiadoideae (Christ
& Schnepf, 1988), Bignoniaceae (Galetto, 1995a; Rivera, 2000a), Bromeliaceae
(Böhme, 1988; Sajo et al., 2004), Costaceae (Newman & Kirchoff, 1992),
Crossosomatales (Matthews & Endress, 2005a), Dipsacales (Wagenitz & Laing,
1984), Haemodoraceae (Simpson, 1993), Iridaceae (Rudall et al., 2003a),
Lamiaceae (Dafni et al., 1988; Petanidou et al., 2000), Liliaceae (Khaniki &
Persson, 1997), Malvales (Judd & Manchester, 1997; Vogel, 2000), Melasto-
mataceae (Stein & Tobe, 1989), Melianthaceae (Decraene & Smets, 1999a;
Decraene et al., 2001), Aizoaceae-Mesembryanthemoideae (Chesselet et al.,
2002), Polygonaceae (Decraene & Smets, 1991a), Rhamnaceae (Medan &
Aagesen, 1995), Solanaceae (Bernardello, 1987; Cocucci & Galetto, 1992),
among others. More importantly, the survey publications on dicot groups by
Smets (1986, 1988) and Smets and Cressens (1988) and on monocot groups
by Daumann (1970), Vogel (1981a), Endress (1995), and Smets et al. (2000)
were fundamental to appreciation of the significant role of nectaries in sys-
tematics and evolution. Nevertheless, their potential impact is still under-
exploited. Taking this background into account, I here summarize the
biodiversity of floral nectaries and their general position and distribution in
gymnosperms and angiosperms, with emphasis on their use in systematic
classifications and phylogenies.
2
NECTARIES IN GYMNOSPERMS
Although most gymnosperms are anemophilous, entomophily has evolved in
Cycadales and Gnetales, albeit differently in each group. In many cycads,
thermogenic cones characterize pollination: here beetles and thrips find re-
wards in the form of food, mating sites and brood sites for larvae, and in
return act as pollen vectors (e.g., Tang, 1987; Donaldson, 1997; Terry et al.,
2004).
The three genera of Gnetales—
Ephedra
(Bino & Meeuse, 1981; Bino
et al., 1984a, b; Meeuse et al., 1990),
Gnetum
(Kato et al., 1995), and
Welwitschia
(Wetschnig & Depisch, 1999)—differ in that their ovules se-
crete a sugary droplet at the micropylar end (Fig. 1), i.e., the nucellar apex of
the ovule (Martens & Waterkeyn, 1974; Moussel, 1980; Carafa et al., 1992),
