Biology Reference
In-Depth Information
Figure 5.
Fungal hyphae (
arrows
) and conidial spores (
arrowheads
) on
Hedera helix
(Arali-
aceae) floral nectary surface. The epidermal cells are covered by ridged cuticle. Bar = 10 µm.
8.4
Variability and experimental design
All these sources of intraplant and intraspecies variability of nectar proper-
ties must be considered before planning experiments on nectar production.
Galetto and Bernardello (2005) provided some recommendations to neutral-
ize this variability:
•
To decrease intraplant variability it is necessary to include flowers of the
same age but different sizes, from different flower stems, or from different
positions in inflorescences, and from different locations within the plant in
each flower set.
•
To decrease within- and between-population variability it is necessary to
include flowers of the same age from different plants and, when possible,
from different populations in each flower set.
•
It is also recommended to concentrate measurements in the same period
and to measure the microclimate (temperature and RH) around or within
the flowers.
We can speculate about the significance of such high potential variability
of nectar traits. Many researchers argue that nectar variability may itself be
adaptive because pollinators encountering variable rewards are more likely
to move from plant to plant, promoting outcrossing. Potts et al. (2004) report
that nectar resource diversity alone explains the majority of variation in bee
species richness in complex communities. It therefore seems that variability
in nectar features is favourable for both plants and visiting animals.
