It's all in the scent: Plant inbreeding reduces attractiveness to pollinators

Researcher from Kiel University use the example of the White Campion to show which effects of habitat destruction threaten the survival of plant populations

The diversity of all animal and plant species, also known as biodiversity, is an important indicator of healthy ecosystems, provides a livelihood for humans in many ways and is thus essential for our survival. However, biodiversity is threatened at both global and local levels by habitat destruction. Looking at the plant world, for example, the destruction but also the fragmentation of habitats often negatively impacts the size of local plant populations. Small plant population have an increased risk of inbreeding: if there are too few and also closely related plants available, offspring are often produced that suffer from reduced fitness. Their low viability and low reproductive success then diminish the chances of survival of the plant population as a whole. A research team from the Department of Geobotany at the Institute of Ecosystem Research at Kiel University has used the example of the White Campion (Silene latifolia) and its pollinating insect, the Lychnis Moth (Hadena bicruris), to investigate the effect of inbreeding in plant populations on the communication with their pollinators and thus plant survival. The researchers in the project, led by Dr Karin Schrieber, a scientist in the Kiel Geobotany department and member of the Kiel Plant Center (KPC), found that especially the plants' scent signals are disturbed by inbreeding, significantly reducing the probability of pollination by the insects. The Kiel scientists from Professor Alexandra Erfmeier’s group, together with researchers from Bielefeld University, recently published their new research results in the scientific journal eLife.

Complex signals control insect pollination

The White Campion is one of the rarer separate-sex plants. In order to reproduce, they depend, among other things, on the help of insects that transport pollen from male to female specimens. The campion is mainly pollinated by one highly specialised insect species, which is the Lychnis Moth. Their specific relationship has developed in the course of co-evolution, in which plant and insect have adapted strongly to each other over long periods of time. As a result, complex communication patterns have developed between plant and insect, consisting of various optical, chemical and spatial signals. The white campion, for example, only opens its white flowers, which are then clearly visible, at dusk or in the dark and emits a scent consisting of around 70 chemical compounds. This is also the time of day when the moth is active and its pollination behaviour is triggered by the plant's signal complexes, from oriented flight towards campion flowers to the extension of its proboscis.

"So we wanted to find out whether and to what extent inbreeding alters these plant signals and how this in turn affects the behaviour of the insects and their pollination service " explains ecologist Schrieber, first author of the new study.

Inbreeding effects on pollination behaviour experimentally deciphered

To test this hypothesis, the Kiel research team first cultivated White Campions under inbreeding conditions. Plant signals such as flower shape and arrangement, scent emission, flower colour and nectar production were analysed under controlled conditions in cooperation with Bielefeld University. The inbred plants had smaller and fewer flowers and smelled differently from plants derived from unrelated parents. In particular, they produced fewer lilac aldehydes, volatile scents that control moth pollination behaviour. To be able to determine the difference between control and inbred plants in pollination, the researchers conducted so-called "common garden" experiments, in which the plants are placed in a habitat that is as natural as possible but at the same time controlled. "We moved the campions to an outdoor area where the moths occur naturally. Here they were positioned in pots of standardised soil with even spacing, sky orientations and surrounding vegetation. The moths could then choose to visit either inbred or control populations. In this way, we found that the inbred flowers were visited significantly less by moths," continues Schrieber, who was financially supported by the Faculty of Mathematics and Natural Sciences at Kiel University. The researchers were able to demonstrate this effect particularly in female plants with a specific geographical origin. They were thus able to prove experimentally that inbreeding makes the plants less attractive to their pollinating insects.

Effects of habitat destruction

The new research, which also involved several students in final semesters at Kiel University, highlights the effects of habitat destruction on plants. "The example of the White Campion and its specialised pollinating insect shows how sensitively the finely tuned communication between plant and insect can react to external disturbances”, summarises Schrieber. Inbreeding effects are only one factor in the interplay of numerous influences that have a negative impact on biodiversity when habitat loss occurs. "If we look at these variables as a whole, research work like this helps us to develop measures against the loss of biodiversity based on ecological models," emphasises Erfmeier. The current publication thus further contributes to the Department of Geobotany’s and the Kiel Plant Center’s efforts to investigate the relationships between the environment and the plant world against the background of global change.

Scientific contact:

Dr Karin Schrieber
Department for Geobotany
Institute for Ecosystem Research, Kiel University
+49 (0) 431-880-4082




More information:

A white flower
© Roman Adler

The object of study: the flower of a female White Campion.

White flowers at dusk

© Roman Adler

A member of the research team from Kiel Geobotany observing pollinators on the White Campion at dusk.

A scientist in between flowers in a greenhouse
© Roman Adler

One of the participating students recording data on spatial flowering signals in the greenhouse. 

a moth on a flower

© Zoran Bozovic, Saxifraga Foundation, Lizenz: CC BY-NC-SA

The Campion Owl at the flower of a male White Campion.

Original publication:

Karin Schrieber, Sarah Catherine Paul, Levke Valena Höche, Andrea Cecilia Salas, Rabi Didszun, Jakob Mößnang, Caroline Müller, Alexandra Erfmeier, Elisabeth Johanna Eilers (2021): Inbreeding in a dioecious plant has sex- and population origin-specific effects on its interactions with pollinators. eLife First published May 14, 2021  

DOI: 10.7554/eLife.65610.sa2

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