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

Summary
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Episcia lilacina produces single flowers of zygomorphic symmetry in the leaf axils. The five
petals are fused, forming a hypocrateriform flower. This suggests butterfly pollination. Further
indications are sensitive flowers with a lilac-coloured limb, nectar hidden in a spur, with a long
distance between sexual organs and nectar.
Pollinators with shorter proboscis can be excluded as legitimate pollinator because of the
length of tube of Episcia lilacina. Further on, the narrow entrance prevents that pollinators
penetrate too far into the tube and ensures that the insects are positioned correctly to come in
contact with the anthers or the style.
From the stage at which the flower bud is clearly recognizable to the stage at which the bud is
shortly before opening, about 19-23 days have past. During this period the corolla has grown in
length and developed an anterior globular section equivalent to the limb of the later flower.
The flowers of Episcia lilacina are proteandrous. The male stage begins shortly after the
opening of the flower and ends about 12 hours later with coiling the filaments. Afterwards the
style starts to grow in length and after a few couple of hours the female stage begins with the
stigma becoming receptive. After two days, when the stigma lobes shrivel, anthesis ends.
The fruit of Episcia lilacina is a capsule with globular, reddish or white seeds, surrounded by a
persistent calyx. Over the course of 25 days the fruit grows averagely 5,5 mm in width and 4 mm
in length.
The fruit set of Episcia lilacina is 19%. Self-pollination can be excluded. Manual selfpollination
is possible, but spontaneous self-pollination does not occur, for the simple reason of
protandry. Sexual reproduction is largely replaced by stolon spreading.
The P/O ratio of Episcia lilacina is 36,34/1. Due to Cruden (1975) this would indicate obligate
autogamy. But this can be definitively excluded. One possible explanation is pollen agglutination,
which enhances the efficiency of pollen transfer and was observed both with Episcia lilacina and
other species of Gesneriaceae.
The production of nectar starts a couple of hours before the flower of Episcia lilacina opens.
The maximum amount of secreted nectar by one flower was 5,4 µl. Further on, the nectar has a
sugar concentration of 27%. Both facts indicate butterflies as legitimate pollinators.
The only observed flower visitor of Episcia lilacina during the investigation period was a
species of stingless bees (subfamily Meliponinae). These bees are not the legitimate pollinators,
but secondary ones, which do, however, not fit into the pollination syndrome.
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