Pollination: Air pollution renders flower odors unattractive to moths


Date:
September 4, 2020
Source:
Max Planck Institute for Chemical Ecology
Summary:
Researchers showed that tobacco hawkmoths lost attraction to the
scent of their preferred flowers when that scent had been altered
by ozone. This oxidizing pollutant thus disturbs the chemical
communication between a plant and its pollinator. However, when
given the chance, hawkmoths quickly learn that an unpleasantly
polluted scent may lead to nutritious nectar.



FULL STORY ==========================================================================
A team of researchers from the Max Planck Institute for Chemical Ecology
in Jena, Germany, and the University of Virginia, USA, has studied
the impact of high ozone air pollution on the chemical communication
between flowers and pollinators. They showed that tobacco hawkmoths
lost attraction to the scent of their preferred flowers when that scent
had been altered by ozone. This oxidizing pollutant thus disturbs the interaction between a plant and its pollinator, a relationship that
has evolved over millions of years. However, when given the chance,
hawkmoths quickly learn that an unpleasantly polluted scent may lead to nutritious nectar.


========================================================================== Pollination in the Anthropocene Pollination is a critical ecosystem
service, one that is performed mainly by insects. Flowers attract insects
using floral scents, which are chemical signals that the pollinators
can have an innate preference for. This preference is the result of the co-evolutionary relationship between flowers and their pollinators that
has evolved over millions of years.

For about 20 years, the term "Anthropocene" has been used in the
scientific community to refer to the geological epoch in which
humans are responsible for many changes in biological and atmospheric processes. However, until recently, little has been known about the
effects of anthropogenic climate change and atmospheric pollution on
natural environmental odors that drive chemical communication between organisms.

A team of researchers from the Max Planck Institute for Chemical Ecology
and the University of Virginia has investigated whether human-driven
ozone pollution in the air influences the attraction of a pollinating
moth to the scent of one of their favorite flowers. Ozone is an oxidant,
a highly reactive chemical and pollutant known to cause respiratory
diseases in humans. Now, ozone is also thought to change the floral
scents that flowers emit to attract their pollinators.

For their experiments, the scientists used the tobacco hawkmoth Manduca
sexta.

"The hawkmoth Manduca sexta is the perfect model for our study. Although
it is highly attracted by flower odors, it also uses its visual system
to locate flowers. Flowers that usually attract hawkmoth often share
specific compounds in their blend and are visually very conspicuous due
to their bright white color," says study leader Markus Knaden, who heads
a research group in the Department of Evolutionary Neuroethology at the
Max Planck Institute.



==========================================================================
The research team first determined the exact compositions of the flower
odors - - with and without increased ozone content -- and the respective concentrations of individual odor components using gas chromatography. For
the ozone-altered odors, the researchers used ozone concentrations
that can be measured on hot days in the natural habitat of tobacco
hawkmoths. They tested the responses of the moths in behavioral assays
in a wind tunnel, allowing the insect to investigate both the original
floral odor and to the ozone-altered floral odor.

"We were surprised, even shocked, that the innate attraction to the odor
of tobacco flowers was completely lost in the presence of increased ozone levels," said Knaden, describing what was observed during the experiments.

Tobacco hawkmoths are able to learn The question remained whether ozone in
the air would spoil the appetite of hungry and foraging tobacco hawkmoths,
or whether it would prevent insects from finding their food source. Would insects be able to figure out that even polluted flower odors can offer rewards? To answer this question, researchers tested whether tobacco
hawkmoths could learn to accept an initially unattractive scent as a
food cue if they smelled it while simultaneously being offered a sugar
solution reward. The researchers assessed several different ways in
which the moth could learn to recognize flowers based on the ozone-
altered floral scent. This was critical to relating these experiments
to real- world learning. In the real world, a floral scent only becomes ozone-altered as it moves downwind of the flower and mixes with ozone. To
see if moths could learn ozone-altered floral scents even when they are decoupled from the sugar reward at the flower, the researchers developed
an experiment where the moth had to follow the ozone-altered odor to
the flower, but were presented with the original scent at the flower
containing the sugar reward.

"While we anticipated that Manduca sexta could learn new floral scents
and hoped that they would be able to learn the polluted floral scent
of their host flower, we were amazed to see that Manduca sexta could
learn the polluted floral blend in a number of different ways, including learning a polluted scent that was decoupled from a sugar reward. This
type of learning, which we were surprised to find in Manduca sexta,
could be very important in insects' ability to use learning to cope with
their rapidly changing environments," says first author Brynn Cook from
the University of Virginia. What is especially noteworthy and pertinent
about this kind of responsiveness to a changing environment is that it
occurs in real time and not over evolutionary timescales.

Learning ability of Manduca sexta is not an all-clear Although the study
shows that tobacco hawkmoths can learn to rely on ozone- altered and
initially unattractive plumes to recognize their flowers, air pollution
still poses a serious risk to pollination and pollinators. "Learning
may be key to insects recognizing their host plants in polluted
environments, but one of the major questions remaining from our study
is whether pollinators will be able to find their flowers in the first
place. Without initially recognizing smells, will pollinators only
have visual cues to help them locate host flowers in order to learn the pollution-altered floral scent? Another important aspect to consider is
that other pollinators may not have the same facility to learn new smells
that Manduca sexta has. Specialist pollinators, for instance, may not have
that flexibility in learning. Our study is just a starting point. Field
studies are going to be critical to understanding which flowers and
insects are most affected by which pollutants, and likely why," says Cook.

Air pollution and climate change have far-reaching consequences for our ecosystem; by no means have all of these been studied and understood. For example, we still know little about the impact of atmospheric changes
on the chemical communication between plants and insects. Not only are
plant odors altered, but also the sex pheromone female insects use to
attract males.

Atmospheric changes have the potential to cause alterations in
pheromones that could lead to mating failure. Insect mortality has risen dramatically in recent years, and researchers worldwide are searching
for the causes. Since 2020, the Max Planck Center next Generation Insect Chemical Ecology, a cooperation between the Max Planck Society and two
Swedish universities in which the Max Planck Institute for Chemical
Ecology and the co-authors of the study, Bill Hansson and Markus Knaden,
play a major role, has been dedicated to this field of research.


========================================================================== Story Source: Materials provided by
Max_Planck_Institute_for_Chemical_Ecology. Original written by Markus
Knaden. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Brynn Cook, Alexander Haverkamp, Bill S. Hansson, T'ai Roulston,
Manuel
Lerdau, Markus Knaden. Pollination in the Anthropocene: a Moth Can
Learn Ozone-Altered Floral Blends. Journal of Chemical Ecology,
2020; DOI: 10.1007/s10886-020-01211-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200904101806.htm

--- up 1 week, 4 days, 6 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)