What, exactly, is a biotic interaction?

Bob O'Hara

Senckenberg BiK-F

Frankfurt am Main

Germany@bobohara

slides:

– www.slideshare.net/oharar/what-exactly-is-a-biotic-interactions

Thanks to - Damaris Zurell

Laure Gallien

Jens-Christian Svenning

Lesley Lancaster

Katja Schiffer

For comments & organisation

Are these animals interacting?

Photo: “sea war, 1 of 8 - no, you can't have it” by Sean Hoyer https://flic.kr/p/qHjzk

Are these animals interacting?

Photo: Tim Felce (Airwolfhound) [CC BY-SA 2.0], via Wikimedia Commons

Two Dissections

Direct and Indirect Interactions

Processes and Outcomes

Processes and Outcomes

For many biotic interactions, the species do not actually interact

Source: U.S. Navy NAVSUPFAC DIEGO GARCIA, Natural Resources Management Plan, 2005: http://bit.ly/1OTt6vz

Source: http://www.bees.unsw.edu.au

Competition ≠ Interaction?

Scramble Competition (for resources)

"Scarabaeus laticollis" by Rafael Brix - [CC BY 2.5] via Commons http://bit.ly/1QcgXDa

Mutualism

No direct Interactions

"Cows at dawn" by fir0002 [GFDL 1.2] via Commons - http://bit.ly/1lqEN1I

Grass can be a limited resource for grazing cows

Outcomes

Biotic Interactions!

Changes in community structure due to changes in other parts of the community

Process ≠ Outcome

Try not to confuse outcome with process

Scramble competition is only an interaction because of its effect

What is a biotic interaction?

When is a process a biotic interaction?

Photo by Janderk (Jan Derk) [Public domain], via Wikimedia Commons

Not a Biotic Interaction

Species 1 Species 2

Environment

Two species affected by the environment

Direct Interactions

One species does something to another

Species 1 Species 2

Predation Parasitism

Herbivory Pollination

Seed Dispersal

Mediated Interactions

Species 1 Species 2

Environment

Two species affect the environment

Scramble Competition Ecosystem engineering

Shading

Indirect Effects

Species 1 Species 2 Species 3

PlantHerbivore/PreyPredator

Is there a biotic interaction between plant and predator?

Trophic cascades?

Apparent Competition

Helpless Prey 1

EvilPredator

Helpless Prey 2

Is there a biotic interaction between prey species?

Spot the Difference

Does it matter if indirect effects go through a biotic or abiotic component?

Prey 1

Predator

Prey 2Species 1 Species 2

Environment

Spot the Difference

Does it matter if indirect effects go through a biotic or abiotic component?

Prey 1

Predator

Prey 2Species 1 Species 2

Environment

Perhaps not – because feedback

Is this it?

Feedbacks are important

Biotic Interactions = ecological effects due to individual behaviours with feedbacks

Species 1

Species 2Species 1 Species 2

Environment

What have we learned?

Biotic interactions are about cause and effect

Indirect effects might or might not be biotic interactions

By Janderk (Photographed by Jan Derk) [Public domain], via Wikimedia Commons

Feedback is important

Is this important?

You decide!