ON: Dr. Günter
Gerlach, how long have you been studied orchids and, particularly, fragrances
GG: I started as orchid gardener in 1979 in the
botanical garden of Heidelberg in Germany, worked there in this position
2 years and then studied biology at the same university. So I can say
that I am studying orchids for more than 25 years. My fragrance investigations
started with my doctoral thesis nearly 20 years ago. Looking for the
pollination biology was the consequent next step immediately after having
the first positive results in fragrance investigation.
ON: Your lecture concerned the "Pollination and fragrances in the
tribe Maxillarieae". Could you develop a little this question?
Which subtribes are circumscribed in the Tribe Maxillarieae?
GG: In the tribe Maxillarieae are included
the subtribes (after Dressler 1993): Cryptarrheninae, Zygopetalinae,
Lycastinae, Maxillariinae, Stanhopeinae, Telipogoninae, Ornithocephalinae,
Oncidiinae, all in all more than 2500 neotropical orchids. The species
within this tribe belong to different pollination syndromes which means
that they use different classes of pollinators (female bees, male bees,
flies) appealing at their respective behaviour. The communication between
the flowers and their pollinators in many cases is effected by the floral
ON: All species
included have a scent?
GG: No, there are a lot of genera and species
without perceptible floral scent. Floral scent always is an information
for the respective pollinator, like there are the colour or form too.
Floral scents could be very strong especially in the species belonging
to the perfume flower syndrome, which means that the pollinators are
attracted and rewarded by the fragrance compounds. Only here, male bees
collect the fragrance compounds. Within Tribe Maxillarieae different
pollination systems are involved, there exist perfume offering flowers,
oil offering flowers, and a lot of deceptive pollination systems.
ON: When you
said that the pollination systems in Tribe Maxillarieae are,
some of them, rewarding and, some other deceptive ones, what exactly
the means of this affirmative?
GG: Rewarding pollination systems offer different
forms of reward to their pollinators. The most common rewards are nectar
or pollen. In orchids pollen is not available because of the pollinaria
it would result in a complete pollen loss and so a absolute breakdown
of the pollination system. Orchids offer rewards as nectar, oil, sleeping
places and perfumes. Deceptive ones do not offer anything. The pollinators
are deceived by the flowers having the similar colours, forms or fragrances
as non-deceptive ones. In sexual deceptive flowers male bees are deceived
by flowers looking like their females. So the male begins to copulate
with the flower effecting pollination.
ON: So the species
of this Tribe can have a kind of nectar?
GG: Only a very few species within the Tribe Maxillarieae
have nectar, most species here belong to other pollinating systems.
ON: Why the fragrances
serve to select the bee species?
GG: Normally the fragrances serve as a guide to
the flower which the pollinator remember from a previous visit. In perfume
flower syndrome however, the Euglossine bees are very selective
in their fragrance choice. So an effective isolation between co-occurring
plants belonging to this syndrome exists.
ON: By the way,
concerning the isolation, you also affirmed that bees are so special
in their preferences that result an efective barrier against hybridisation.
What exactly does it work?
GG: We do not understand until now how it works,
because we do not know if the respective bees do not perceive or if
they do not like the special aroma. This means that until now we do
not know if the selectivity corresponds to the lack of receptors in
the bees antenna or in inhibitory connections in the brain.
ON: When the
species are artificially crossed, what is the result concerning the
GG: We have only a very few artificial hybrids
investigated. In a crossing of two Coryanthes species the fragrance
composition was intermediary.
ON: The different
fragrances of flowers are enough to distinguish species even when they
are very similar, what kind of information the fragrance carries? they
give very informative hints for taxonomy but fail in generic level?
GG: Speaking of fragrances of flowers belonging
to perfume flower syndrome the fragrance composition for me is a very
good character to distinguish the species within one genus. Unfortunately
this information gets lost when the flowers are conserved (liquid or
dried) in herbaria. So this information is of limited help for taxonomy.
In generic level it fails because we found in some different genera
the same fragrance pattern. It is very probable that in this cases and
when the different plants occur together both species are pollinated
by the same bee species. This does not result in a intergeneric hybrid
because of the position of the respective pollinaria on the bees body.
ON: Inside this
tribe, which are the most scented genera and species?
GG: Within the Tribe we have a lot of species
of different genera in different subtribes which have an very intense
odour. A lot of Stanhopea and Coryanthes species are found
among those plants with intense smell, but we also find here Anguloas,
Trevorias, Cirrhaeas, Houlletias. Some of them like Stanhopea platyceras,
Houlletia lowiana and Houlletia sanderi have really disagreeable
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