A SYSTEMATIC SURVEY OF FLORAL NECTARIES - Nectaries and Nectar - page 51

Hydrastis is the basal genus for the Ranunculaceae (Ro et al., 1997);
however, scant information is available on the pollination of this genus,
which lacks petals and has caducous sepals. Small bees are the primary pol-
linators (Sinclair et al., 2000), and it seems to have pollen as reward but no
nectar.

3.5.6 Solanaceae

This cosmopolitan family, with its main centre of diversity in South Amer-
ica, offers different kinds of rewards to a broad array of pollinators. It shows
a wide adaptive radiation that includes all forms of animal pollination: by
birds, moths, butterflies, bats, bees, and flies (Cocucci, 1999; Hunziker,
2001). Similarly diverse are the floral rewards that its members can offer,
which include nectar (e.g., Galetto & Bernardello, 1993, 2003), pollen (e.g.,
Symon, 1979; Lester et al., 1999), scents (e.g., Passarelli & Bruzzone, 2004),
and oil (e.g., Simpson & Neff, 1981; Cocucci, 1991).

Solanum is the most diverse and the largest genus in the family, compris-
ing about half of all Solanaceae species (~1,400 spp.). Solanum flowers offer
pollen as reward and are typically buzz-pollinated (Symon, 1979; Buchmann,
1983; Hunziker, 2001). However, most other genera (e.g., Capsicum , Ly-
cium , Nicotiana, Physalis , Schizanthus ) and tribes (e.g., Cestreae, Datureae,
Lycieae, and most Solaneae) are nectariferous, presenting an annular nectary
at the base of the ovary (Bernardello, 1986, 1987; Vogel, 1991; Hunziker,
2001). This widespread nectariferous condition, together with the presence
of nectar in the basal Schizanthoideae and Swenckioideae groups (Olmstead
et al., 1999; Martins & Barkman, 2005; Perez et al., 2006), suggest that nec-
tar as reward is ancestral in this family.

Taxonomically, the presence or absence of nectaries is useful at the
generic and tribal levels. Within a genus, nectary morphology and colour
can be variable among the species; nectary colour is a valuable trait used to
define assemblages of species (Bernardello, 1987; Cocucci & Galetto, 1992).

3.6 Nectaries and deceit pollination

The presence of a reward in flowers of animal-pollinated plants (nectar in
our case) has been thought to allow the evolution of plants with rewardless
flowers that only look (or smell) as if they could offer a reward (Willson &
Ågren, 1989). Such flowers are said to be pollinated by deceit. Although
there are several studies on these kinds of plants (e.g., Williamson, 1982;