1. Storage effects in intermittent river ecology: implications for coexistence, biotic interactions and colonization dynamics
Hydrobaenus sp. (Chironomidae)
diapause in desiccation-resistant case
Intro
Thank you to VT and IRSTEA Photo of Hydrobaenus collected durng my MS project
Ross Vander Vorste
Virginia Water Resources Research Institute, Virginia Tech University
Thibault Datry
IRSTEA, Villeurbanne, France
@RiversRossV
Society for Freshwater Science 2016

2. Biodiversity and community assembly
Environment
Biotic interactions
“Filters”
Regional species pool
Local community
Dispersal
Community assembly
As a freshwater ecologist, I am interested in understanding what produces the vast amounts of biodiversity in freshwater ecosystems
Also, the processes of community assembly or how local communities are formed from the regional species pool
Here, shapes represent different species in the regional species pool and through processes such as dispersal and interactions with the environment and other bioto can come together to form a local community
(Poff 1997 JNABS, HilleRisLambers et al Annu. Rev. Ecol. Evol. Syst.)

3. Biodiversity and community assembly
How is diversity maintained in a fluctuating environment?
Harsh environmental conditions
Environmental fluctuations
Harsh
We now know that the relative importance of these processes or filters change as the environment fluctuates, across a gradient from favorable to harsh conditions
When you think about these harsh conditions such as fires floods and drying these conditions really test local communities, often removing many or most of the species inhabiting a local community
So this brings up an important question “ How is biodiversity maintained in the face of harsh environmental conditions “
This is a question that a lot of scientists are asking themselves considering our changing climate
Favorable
Time

4. Storage effects can maintain species diversity
Population growth during favorable environmental conditions is stored and buffers species from the negative effects of harsh conditions
One way that biodiversity can be maintained is though storage effects
What are storage effects? This is when population growth during favorable environmental conditions is stored and buffers species from the negative effects of harsh conditions
(Chesson 2000 Annu. Rev. Ecol. Evol. Syst.)

5. Storage effects can maintain species diversity
Population growth during favorable environmental conditions can be stored and buffer species from the negative effects of harsh conditions 1
Species have different responses to the environment
Abundance
High
Low
Water availability
Species 1
Species 2
Storage effects can occur when species have different
(Chesson 2000 Annu. Rev. Ecol. Evol. Syst.)

6. Storage effects can maintain species diversity
Population growth during favorable environmental conditions can be stored and buffer species from the negative effects of harsh conditions 1
Species have different responses to the environment 2
Covariance between environment and competition
Competition
High
Low
Water availability
(Chesson 2000 Annu. Rev. Ecol. Evol. Syst.)

7. Storage effects can maintain species diversity
Population growth during favorable environmental conditions can be stored and buffer species from the negative effects of harsh conditions 1
Species have different responses to the environment 2
Covariance between environment and competition 3
Species traits limit the impact of the environment and competition
the seedbank
(Chesson 2000 Annu. Rev. Ecol. Evol. Syst.)

8. How can “storage” influence communities?
Colonization dynamics 1
Early colonizing taxa can have priority effects

9. How can “storage” influence communities?
Colonization dynamics 1
Early colonizing taxa can have priority effects 2
Biotic interactions
Could reduce competition and predation pressure

10. How can “storage” influence communities?
Colonization dynamics 1
Early colonizing taxa can have priority effects 2
Biotic interactions
Could reduce competition and predation pressure 3
Species coexistence
Trade-off between resistant and resilient strategies

11. How can “storage” influence communities?
Colonization dynamics 1
Early colonizing taxa can have priority effects 2
Biotic interactions
Could reduce competition and predation pressure 3
Species coexistence
Trade-off of resistant and resilient strategies
Examples in the literature: ?
Durden images
Adler et al PNAS
Angert et al PNAS
Usinowicz et al ECOLOGY

12. Intermittent rivers as a model system
Environmental fluctuations
Roubion River, France
Before drying
During drying
Bertrand Launay

13. Intermittent rivers as a model system
Environmental fluctuations
Found globally and increasing in abundance
Danube (Germany)
Manganui (NZ)
Tete (Mozambique)
McMurdo Valley (Antarctica)
Kapoeta (Soudan)
Rio Grande (US)

14. Intermittent rivers as a model system
Environmental fluctuations
Found globally and increasing in abundance
Threatened by climate change, water abstraction and other human activities
Pete McBride
Colorado River, USA
Chandravir Singh
Narmada River, India

15. Invertebrate storage in intermittent rivers
Hyporheic zone use during drying
Hyporheic zone
S. Luk
Gammarus pulex
(Gammaridae)
Leuctra sp.
(Leuctridae)
Baetis sp.
(Baetidae)

16. Invertebrate storage in intermittent rivers
Hyporheic zone use during drying
Hyporheic zone
S. Luk
Gammarus pulex
(Gammaridae)
Leuctra sp.
(Leuctridae)
Baetis sp.
(Baetidae)
Resistance forms prevent desiccation
Eggs, body armoring (cases), diapause/dormancy
Mesocapnia arizonensis
(Capniidae)
M. Bogan
M. Billard
Hydrobaenus sp.
(Chironomidae)
Stenophylax latipenis
(Limnephilidae)

17. Storage effects and colonization dynamicsNo
Non-dispersing
colonizers
Dispersing
colonizers
Before
During
After
Vander Vorste et al FWB

18. Storage effects and colonization dynamicsNo
Non-dispersing
colonizers
Dispersing
colonizers
Before
During
After
Invertebrates from the seedbank colonize first
and could have ‘priority’ over dispersing colonizers

19. Cybister tripunctatus
Storage effects and biotic interactions
Large predator
Prey
Before
During
After
Cybister tripunctatus
(Dytiscidae)
Predator
Gammarus pulex
(Gammaridae)
Prey
Prey can use hyporheic zone to avoid biotic interactions
and drying can remove top predators

20. Storage effects and species coexistence
Resilient species
Resistant species
Before
During
After
Invertebrate storage can lead to establishment of ‘early’ and ‘late’ season communities

21. Key research questions
Colonization dynamics
Are there priority effects related to colonization via invertebrate storage?
Study design: species additions to mimic ‘early’ and ‘late’ arriving taxa
Mesocosm experiments

22. Key research questions
Biotic interactions
Does invertebrate storage reduce competition and predation pressure during harsh environmental conditions?
Study design: measure biotic interactions w/ and w/o hyporheic zone
Manipulative field experiments

23. Implications for IRES management
Species coexistence
Can invertebrate populations increase from low population size in the presence of a competing taxa?
Study design: long-term population dynamics
Field observations
Population modeling
Abundance
Species 1
Species 2
Time

24. Broader implications for freshwater ecology
Temporal vs spatial dispersal
Storage could reduce connectivity among meta-communities
Alteration of gene flow among populations
Intermittent river management
Increased duration will reduce importance of storage effects
Importance of protecting invertebrate storage

25. In summary
@RiversRossV
Contact:
Similar to terrestrial systems, storage occurs through the combined use of the hyporheic zone and desiccation-resistance forms by invertebrates in IRES.
Circumstantial evidence suggests that storage influences colonization dynamics, biotic interactions and species coexistence.
Research should be directed towards addressing several key research questions related to storage effects to advance IRES ecology.