Leaf colour patterns, vegetative and sexual reproduction of Episcia ...

Research in the tribe Sinningieae revealed an average amount of nectar of 15,4 µl (±12,1 µl
standard deviation) for bee pollinated flowers (Perret et al. 2001). For Drymonia serrulata
(Gesneriaceae), a plant that is mostly visited by large neotropical bees, an average of 262,3 µl
(±95,9 µl standard deviation) has been published (Steiner 1985). Opler (1983), however, gives
values of 9,75 µl for medium to large bee pollinated species and 0,93 µl for butterfly pollinated
species. Reddi (1998) investigated among others “tubular flowers with the essential organs
inserted” which were pollinated by butterflies. She found a range from 0,01 to 2.0 µl nectar
volume. These statements point to butterflies as the legitimate pollinators of Episcia lilacina due to
the fact that the amount of presented nectar is far below the average of melittophilous flowers.
With higher concentrations of sugar in the nectar the amount of contained energy increases.
At the same time its viscosity increases too, resulting in a higher amount of energy requirement
for the pollinator during the uptake of the nectar. The „optimal sugar concentration for floral
nectar” represents the sugar concentration at which the rate of net energy gain to the pollinator is
maximized. It is around 26 % (Heynemann 1983). Episcia lilacina is quite close to that value with
its 27% of sugar concentration.
Heyneman (1983) published a table containing the average sugar concentrations of flowers in
context with their pollinators. Flowers pollinated by butterflies have an average sugar
concentration of 25%, those pollinated by bees however a higher concentration of 35%. Similar
values are presented by Pyke and Waser (1981), namely 28.8 % for butterflies, 22.1 % for
hawkmoths and 41.6 % for bees. In relation to these facts the sugar concentration of Episcia
lilacina of 27% points again towards butterflies as legitimate pollinators.
Flower Visitors
Field studies on pollination on Gesneriaceae are still scarce (Vogel 1966, San Martin-Gajardo
and Sazima 2002a, 2002b). Whieler (1978) described Episcia lilacina as the only known case of
psychophily in the Episcia complex. Afterwards nobody paid attention to the pollinators of
Episcia lilacina any more. During the investigation period the legitimate pollinator could not be
detected, though the flowers did not remain completely unvisited.
Materials and Methods: To verify the statement of Whieler (1978) numerous observations
during the investigation period (May to August 2006) were made. To find the pollinator,
observations of the flowers of Episcia lilacina took place on different spots during different
periods. Especially in the morning hours after the opening of the flowers the arrival of visitors
has been observed. Additionally, an observation of twelve hours – continuously from 4 a.m. to 4
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