Seed dispersal

Seed dispersal is a vital stage in a plant’s life cycle, being the only time at which plants can move any appreciable distance. An understanding of this process is fundamental if we are to answer questions such as:

  • how quickly plants can colonise new habitat, e.g. in restoration activities
  • how we can control invasions by pest and alien plants
  • whether plants will be able to migrate to track climate change
  • what is the evolutionary basis of seed dispersal by animals

Seed dispersal is notoriously difficult to measure because plants generally produce many small seeds which can travel long distances. We are developing methods for measuring dispersal and attempting to understand and model the dispersal process.

Heather seed dispersal

Heather Calluna vulgaris and bell heather, Erica cinerea, are the most important species in dry heathland, an endangered habitat. The seeds of these species are extremely small (Calluna has seeds 0.6 mm in diameter), are produced in enormous quantities (a Calluna plant can produce >7 million seeds in one season) and are transported by wind. We trapped seeds up to 80 m from plants, the furthest a dispersal curve has been measured for a non-tree species. We have used these data to show that conventional wisdom about the patterns of seed dispersal, and also previous mathematical models used to describe dispersal, are both incorrect when applied to these long distances.

 

 

Dispersal in grassland herbs

Grasslands are subject to a wide range of management regimes and we have been studying how management affects seed dispersal in important grassland herbs. An early experiment showed that the cutting of hay increased dispersal distances for yellow rattle Rhinanthus minor but not for ox-eye daisy Leucanthemum vulgare. This was because of differences in seed morphology and seasonal seed production. It also explained differences in the rate at which these species colonised grassland. More recent work on Rhinanthus has measured, for the first time, how dispersal varies among different habitats.

Ant dispersal of gorse seeds

Dwarf gorse Ulex minor seeds have a small food body, called an elaiosome, which attracts ants of certain species. These ants pick up the seed and take it back to the nest, where the elaiosome is removed and eaten and the seed is then discarded. As well as dispersing the seed, this behaviour may place the seed in improved conditions for germination and seedling establishment. Our work on this system has involved observing and measuring dispersal in the field and studying the chemical ecology of the ant-seed interaction. The latter has shown for the first time that the elaiosome produces a chemical which attracts ants from a distance.

On-going work

We are starting to use these dispersal measures in models which predict the spatial dynamics of communities, also the colonisation and invasion potential of plants in new habitats.

Recent publications

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