Biology Reference
In-Depth Information
Little, 1983; Dafni, 1984; Willson & Ågren, 1989; Nilsson, 1992), many
species remain to be recognized and described as such. Some examples fol-
low.
3.6.1
Apocynaceae
In Apocynaceae
s.l.
, most species are nectariferous. They possess either an
annular ovarian nectary, a receptacular nectary (either surrounding the ovary
or as two glands alternating in position with the two carpels), or have carpel-
lodes transformed into nectaries (Rao & Ganguli, 1963; Boiteau & Allorge,
1978; Galetto, 1997). In some taxa, however (
Plumeria
,
Himatanthus
,
Nerium
,
Aspidosperma
), nectar is not produced, because the nectary be-
comes inconspicuous and non-functional (Woodson & Moore, 1938; Haber,
1984; Herrera, 1991; Lin & Bernardello, 1999). Despite lacking nectar, other
floral features together with massive flowering in these taxa attract naïve
visitors, which are deceived into pollinating the flowers. Although data are
insufficient, deception in this family seems to be derived and to have arisen
several times in the Apocynoideae and Rauvolfioideae clades (Potgieter &
Albert, 2001), suggesting that there are factors in common that predispose
members of the family to this trend.
3.6.2
Bignoniaceae
The same situation is true for members of the mainly tropical Bigno-
niaceae—primarily centered in northern South America—most representatives
of which have nectar as reward. The nectar is exuded from an annular ovarian
nectary (Galetto, 1995a; Rivera, 2000a), a character that can be considered
ancestral for the family. Nevertheless, in a few taxa from tribe Bignonieae
(
Cydista
,
Clytostoma
,
Phryganocydia
, and some species of
Lundia
; Gentry,
1980, 1982; Rivera, 1996, 2000a), the nectary is non-functional and the
species are thought to be pollinated by deceit. As this tribe (Spangler &
Olmstead, 1999) and the “mimetic clade” within it are considered to be
derived (Lohmann, 2006), this condition can be regarded as derived as well
and it seems to have evolved once in the group. In
Lundia cordata
, a species
that has lost its ovarian nectary, nectar is secondarily produced from pluricel-
lular corolla trichomes (Lopes et al., 2002); as the presence of an ovarian
nectary is considered an apomorphy for the genus, these authors suggested
that reversal from deceit to nectariferous flowers has taken place in some
taxa of
Lundia
.
