Directed dispersal by an abiotic vector: wetland plants disperse their seeds selectively to suitable sites via water
Merel Soons
Ecology & Biodiversity group
Institute of Environmental Biology
Utrecht University
Overview
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Why is dispersal important?
Movement ecology…
… of plants
Dispersal of wetland plants
Directed dispersal?
Why is dispersal important?
• Natural landscape dynamics
+ Habitat loss, fragmentation and restoration
+ Climate change
→ Plants need to disperse to survive
Essential for understanding and predicting current & future
plant species dynamics
and effective planning of conservation & restoration
activities
Movement ecology
• Movement: change in spatial location of an individual
• More than just the trajectory:
– why move?
– how to move?
– when and where to move?
– ecological and evolutionary causes and consequences
A general conceptual framework for movement ecology, composed of three basic
components related to the focal individual (yellow background) and a fourth basic
component (turquoise background) referring to external factors affecting its movement.
When to move?
(start and stop)
Nathan et al. PNAS 2008;105:19052-19059
©2008 by National Academy of Sciences
Why move?
• Three main hypotheses on advantages of seed dispersal for species survival:
• Escape hypothesis
– Escape from disproportionate mortality near parent
Howe & Smallwood
Ann. Rev. Ecology and
Systematics, 1982
Why move?
• Three main hypotheses on advantages of seed dispersal for species survival:
• Escape hypothesis
– Escape from disproportionate mortality near parent
• Directed dispersal hypothesis
– Only way of reaching special habitat
Howe & Smallwood
Ann. Rev. Ecology and
Systematics, 1982
Why move?
• Three main hypotheses on advantages of seed dispersal for species survival:
• Escape hypothesis
– Escape from disproportionate mortality near parent
• Directed dispersal hypothesis
– Only way of reaching special habitat
• Colonization hypothesis
– Colonization of dynamic habitat
Howe & Smallwood
Ann. Rev. Ecology and
Systematics, 1982
How to move?
→ Movement path
• Plants can disperse
– by clonal expansion
– by wind
– by water
– by hitching rides on animals
– by harvesting or scatterhoarding animals
– by humans
Wichmann et al.
Proc. Roy. Soc. B
2009
Soons
Applied Vegetation Science
2006
Soons
Applied Vegetation Science
2006
Low terminal velocity
High terminal velocity
Soons et al.
Ecology 2004 a
De Jager et al.
Unpublished data
Soons et al.
Journal of Ecology
2016
Kleyheeg PhD
thesis 2015
How to move? Conclusions
• Plant species have specific adaptations to disperse by specific vectors
• Interplay between plant traits and environmental conditions determines how to move – and the movement trajectory
• Plants control ‘how to move’! Where to move?
• If plant species would be able to direct their seeds to suitable sites, dispersal would greatly increase their fitness…
Soons et al.
Functional Ecology
2016
Where to move?
• Plant species have specific adaptations to disperse by specific vectors
– plants invest in dispersal traits
– which favor certain dispersal mechanisms
– and hence deposition at specific sites
– where they germinate best
– and survive as adults
• Traits evolved to help plants reach specific sites as best they can
• Plants control ‘where to move’! Directed dispersal
When to move?
• Are plants dull and passive, or…
Synchrony of seed dispersal, hydrology and local
climate in a semi-arid river reach in California
Populus fremontii
Stella et al.
Ecosystems 2006
When to move? Conclusions
• Plants time their dispersal to match
– suitable environmental conditions for dispersal
– suitable environmental conditions for germination and establishment
• Plants control ‘when to move’
A general conceptual framework for movement ecology, composed of three basic
components related to the focal individual (yellow background) and a fourth basic
component (turquoise background) referring to external factors affecting its movement.
When to move?
(start and stop)
Nathan R et al. PNAS 2008;105:19052-19059
©2008 by National Academy of Sciences
Take home messages
• Movement is more than just the trajectory:
– why move?
– how to move?
– when and where to move?
– ecological and evolutionary causes and consequences
• Plants use a combination of vector (‘how’) and timing (‘when’) of movement to optimize dispersal to suitable sites (directed dispersal) Acknowledgements
Jos Verhoeven
Bart Nolet
Ran Nathan (HUJI)
Arjen de Groot
Gabriel Katul (Duke U)
Teresa Cuesta
James Bullock (CEH NERC)
Monique de Jager
Gustavo Pazos (CONICET)
Sandra Robat
… and many students!!!
Betty Verduyn
Acknowledgements
Rob Fraaije