Biology Reference
In-Depth Information
Table 2.
Different nectar attributes of viscous and non-viscous nectars of 1-day flowers of
Phlomis fruticosa
collected on 28-29 April 1992 in the phryganic habitat of Daphni, Athens.
Values are averages ± SE followed by the results of statistical analyses (Mann-Whitney
U tests).
Nectar attributes
Viscous
nectar
Non-viscous
nectar
M-W U test
Total content (nmole/flower)
Amino acids
18.7 ± 1.75
5.22 ± 0.82
U
(8,16)
= 2, P <0.001
Sugars
6,880 ± 3,354.4
3,834 ± 2,504.2
U
(8,10)
= 20, P >0.05
Sucrose/hexose ratio
S/(G+F) (in weight)
4.7 ± 0.72
3.3 ± 0.62
U
(8,10)
= 6, P <0.01
S/(G+F) (in moles)
2.5 ± 0.38
1.7 ± 0.32
U
(8,10)
= 6, P <0.01
nectariferous. In the Daphni
phrygana
community Petanidou (1991) found
that only 12.4% of the species were nectarless (
n
= 133), but from the rest
only 13.5% produced considerable quantities of nectar. In a more detailed
study within the same
phrygana,
Petanidou and Smets (1995) and Petanidou
(2005) found an average nectar secretion of 0.64 ± 0.246 µl per flower
(
n
= 76 species). However, this substantial average was due to only a few
abundantly nectar-secreting species. When three of the abundant nectar pro-
ducers were removed, average secretion dropped by almost one third.
Nectar concentration (quality) in Mediterranean habitats is generally
higher than in temperate communities (Beutler, 1930, 1953a, b; Cruden
et al., 1983). Beutler (1930) found that the concentration of flower nectars of
18 species visited by honeybees ranged from 10-70%. von Frisch (1967)
examined 65 species and found a similar range. The concentration found by
Cruden et al. (1983) was 32.5 ± 2.46% (
n
= 12). On the other hand, Herrera
(1985) found that in a Spanish
garrigue
most species had very concentrated
nectars, usually higher than 60%. In the Greek
phrygana
, the community
average concentration was 55.4 ± 1.69% w/w sucrose (
n
= 68). The species
average concentration reached 76% w/w sucrose, while that of individual
flowers could exceed 80% (Petanidou & Smets, 1995). In extreme cases
(e.g.,
Urginea maritima, Anthyllis hermanniae
), nectar may even crystallize
in all flowers within a population and it cannot be sampled using capillaries
(Petanidou, personal observations). Regardless of the small volumes detected
in
phrygana
, the total amount of per flower nectar sugars is comparable to
other temperate systems (Cruden, et al., 1983; Petanidou & Smets, 1995).
The low nectar volume in
phrygana
coupled with a high energetic content is
almost certainly related to water limitations in the Mediterranean area.
