Biology Reference
In-Depth Information
combined in several successional stages in order to attain the maximal floral
and bee diversity in a habitat (see also Petanidou & Ellis, 1996).
5.7
What types of nectars do pollinators prefer?
In the Mediterranean, as in many other regions and habitats, nectar profile
(i.e., secretion and characteristics) is sometimes strongly related to the plant's
main pollinator guilds (Baker & Baker, 1983; Petanidou, 2005; Petanidou
et al., 2006). This may be reflected in differences in the nectar profile of ge-
netically closely related plant species that are pollinated by different insect
guilds. The pollination of several species and subspecies of
Capparis
in
Israel is a case in point. The nectar of
C. ovata
, a hawkmoth-pollinated spe-
cies, is higher in volume and concentration than that of
C. spinosa
, a bee-
pollinated species, which occurs in the same localities
and has a similar
flower morphology (Dafni et al., 1987). In addition, the two subspecies of
C. spinosa
in Israel were found to have different nectar profiles: a hawk-
moth-pollinated subspecies with high nectar yield and a bee-pollinated one
with lower nectar volume and concentration (Eisikowitch et al., 1986).
Within the Mediterranean, however, cases like
Capparis
are not com-
mon, as this genus represents an exception for many reasons. Aided by a
very efficient water economy,
Capparis
is a thriving genus in the Mediterra-
nean region where it manifests diverse pollination systems and exceptional
traits such as summer flowering and showy nocturnal flowers with unusually
high nectar rewards (Rhizopoulou, 1990; Petanidou et al., 1996; Rhizopoulou
et al., 1997). In fact,
Capparis
provides the most abundant nectar reward
within Mediterranean scrub, with a recorded nectar volume of 15.21 µl per
flower—about 24 times as much as the community average (0.64 µl)
(Petanidou & Smets, 1995). On the other hand, a phryganic community en-
compasses an outstanding diversity of ordinary plant species that, unlike
Capparis
, follow the “system rules,” by flowering mainly within the major
blooming period (i.e., spring, from March to May) and having small, diurnal,
and low-nectar-yielding flowers (Petanidou et al., 1995; Petanidou & Smets,
1995). Such habitats also contain an exceptional diversity of flower-visiting
insects of particular taxonomic and ecological guilds (Petanidou & Ellis,
1993, 1996). This raises the question of whether, at the community level,
there is a possibility of matching insect guilds and plant species on the basis
of their nectar attributes. Petanidou et al. (2006) attempted to address this
question in a community study and their results are summarized below:
1.
Relationships with insects are more significant in distinguishing plant
assemblages characterized by particular nectar traits than other plant
