Does seedling defence vary over large geographical scales?

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Do the defence mechanisms employed by seedlings to avoid being eaten by herbivores vary according to their location?

That is the question being asked by scientists at the University of Plymouth as part of a new three-year project funded by the Leverhulme Trust.

Previous studies have demonstrated that seedlings use a variety of means, including odours – or volatile organic chemicals (VOCs) – to ward off potential predators.

However, researchers from the University’s School of Biological and Marine Sciences and the German Centre for Integrative Biodiversity Research (iDiv) in Leipzig, want to focus on whether these various chemical defences vary between populations and geographical regions.

Specifically, they will assess whether latitude and altitude make any difference to the plants’ resistance, with research being planned in areas across north and western Europe.

The study is being led by Dr Mick Hanley, Associate Professor (Reader) in Plant-Animal Interactions, who has been studying in this field for more than two decades.

It will focus on the feeding behaviour of snails, who will be presented with seedlings from different regions to see which they prefer.

Researchers will examine the snails’ choices against patterns of chemical compounds present in the seedlings, and then rank the plants according to their acceptability to a generalist herbivore.

They hope this will enable them to identify and quantify population and regional-level variation in the metabolic products associated with various biological processes, including plant defence and variation in local climatic conditions.

Dr Hanley said:

“As with many aspects of plant-herbivore interactions, previous studies have focused solely on the relationships between established plants and their herbivores, which seldom results in plant mortality. For seedlings, however, escaping herbivory is usually a life-or-death issue, and the selective consequences for the individual much more extreme.

“As a result, we might expect to see clearer geographical patterns in the effects of herbivore activity and expression of seedling defence than has been evident for mature plants. But an understanding of population-specific responses will demonstrate by what means, and how consistently, the seedlings avoid or cope with being eaten by herbivores. It may also shed light on recent failures to corroborate theories predicting changes in plant defence across broad geographical ranges.”

School of Biological and Marine Sciences

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