Biology Reference
In-Depth Information
2.3
Plant species with no nectar
An important feature of Mediterranean plants is the absence of nectar from
plants that one expects to be nectar-rewarding, based on their floral display.
Such non-nectariferous species occurring in the Mediterranean region can be
grouped into three major categories:
1.
Species with nectarless deceit flowers, very commonly found in Orchida-
ceae in the region (Dafni & Bernhardt, 1990; Dafni & O'Toole, 1994). In
deceptive pollination, pollinators are offered no floral reward, i.e., no
nectar or pollen, for their visits to orchids (Dafni, 1984). Considering the
high number of deceptive orchids in the Mediterranean area, it may be
concluded that such a rewardless investment service may be of highly
selective significance here. For instance, orchids comprise ~4% of the
total angiosperm flora of the island of Lesvos, Greece, which may
increase to 5% if all orchid subspecies are considered (Bazos, 2005,
personal communication).
2.
Species with differential investment in advertisement versus little or no
reward. This group includes genera with showy flowers that have little or
no nectar, and that use “discovery advertisement” sensu Dafni (1996),
such as geophytes with autumnal flowering and hysteranthous foliage
(e.g.,
Colchicum, Cyclamen, Crocus
). It also includes plants with big and
showy flowers blooming in spring, like
Acanthus spinosus
and
Bellardia
trixago
, both with large white flowers (Petanidou, 1991). Although the
rationale for the existence of such nectarless species would fit with that
of deceptive pollination in the Mediterranean, the selection process to-
wards flower emptiness is totally unknown for either species.
3.
Species with differential investment in pollen versus nectar, both as adver-
tisement and reward, which includes anemones (
Anemone
), poppies
(
Papaver
,
Glaucium flavum
), and nightshades (
Solanum
). Such “pollen
flowers” are common in the Eastern Mediterranean and very important to
bees for pollen alone (Proctor et al., 1996). Other genera bearing less
conspicuous and consequently less competitive pollen flowers (e.g.,
Hypericum
), may be favoured by flowering during a less competitive
period, i.e., towards summer, and then receiving pollinator services
through necessity (Petanidou, 1999).
