1. Collaborative research project:
Explaining variation in functional composition of benthic communities across multi-scaled environmental gradients in the western United States
Collaborative research project:
N. LeRoy Poff
& Brian P. Bledsoe R

2. 197 Study Sites in 9 Ecoregions:
pre-2000 (R)EMAP (snapshot data)
Colorado 59 sites
101 Genera
Oregon 69 sites
119 Genera R
Washington 69 sites
96 Genera

3. Approach for testing:
1) Identify “mechanistic” species traits that respond to environmental conditions.
2) Quantify meaningful environmental filters at different scales.
3) Use hierarchical modeling approach to evaluate predictions of HFM.
(Eco)regional Pool of Species
Multi-scale Habitat Template
Watershed Controls
Valley / Process Domain Controls
Reach / Channel Unit Controls
Microhabitat
Biotic Composition
Hierarchical Filtering
Model (HFM) (Poff 1997)
Species TRAITS

4. Macroinvertebrate traits?

5. 20 traits; 57 states, or ‘modalities’
Traits for North American lotic insects
20 traits; 57 states, or ‘modalities’
Life History:
Voltinism (3)
Development (3)
Emergence Synchronization (2)
Adult life span (3)
Adult exiting ability (2)
Desiccation tolerance (2)
Mobility:
Adult female dispersal (2)
Adult flying strength (2)
Occurrence in drift (3)
Maximum crawling rate (3)
Swimming ability (3)
Morphology:
Attachment (2)
Armoring (3)
Rheophily (3)
Shape (2)
Respiration mode (3)
Size at maturity (3)
Ecology:
Habit (5)
Feeding mode (5)
Thermal preference (3)
Given available traits, which ones can we choose? Pick ones that have “mechanistic” link to environmental variables we have!

6. 20 traits; 57 states, or ‘modalities’
Traits for North American lotic insects
20 traits; 57 states, or ‘modalities’
Life History:
Voltinism (3)
Development (3)
Emergence Synchronization (2)
Adult life span (3)
Adult exiting ability (2)
Desiccation tolerance (2)
Mobility:
Adult female dispersal (2)
Adult flying strength (2)
Occurrence in drift (3)
Maximum crawling rate (3)
Swimming ability (3)
Morphology:
Attachment (2)
Armoring (3)
Rheophily (3)
Shape (2)
Respiration mode (3)
Size at maturity (3)
Ecology:
Habit (5)
Feeding mode (5)
Thermal preference (3)
Disturbance Tolerance: which traits indicative??

7. Disturbance Tolerance
(Eco)regional Pool of Species
Multi-scale Habitat Template
Watershed Controls
Valley / Process Domain Controls
Reach / Channel Unit Controls
Microhabitat
Trait Composition
Hierarchical Filtering
Model (HFM) (Poff 1997)
bi/multivoltine OR
abundant drifter OR
strong swimmer OR
strong flyer
Disturbance Tolerance
bi/multivoltine OR high drift OR
strong swimmer OR strong flyer
mean = 0.23
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0 10 20 30 40 50 60 70 80 90
100
Weedy Species
Number of Sites
Proportion of Assemblage
What environmental factors and at what scales represent “disturbance”?
-> WS flow regime
-> Local bed stability

8. WATERSHED SCALE (15) Geomorphic (2) Geology (3) Climate (3)
Hydrology (4)
Land Use (3)
[GIS]
(Eco)regional Pool of Species
Multi-scale Habitat Template
Watershed Controls
Valley / Process Domain Controls
Reach / Channel Unit Controls
Microhabitat
Trait Composition
Hierarchical Filtering
Model (HFM) (Poff 1997)
VALLEY (link) SCALE (7)
Geomorphic (4)
Land Use (3)
[GIS,
field]
REACH SCALE (11)
Geomorphic (4)
Riparian (3)
Substrate (4)
[EMAP,
Field]

9. Disturbance Tolerance (Model R2 = 0.68)
Reach Scale
Watershed Scale
Valley Scale
Filters
0.23
= 197 n
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0 10 20 30 40 50 60 70 80 90
100
Weedy Species
Number of Sites
Proportion of Assemblage
X = 0.23
0.22
= 152 n
Yes No
0.27
= 45
W_G - Specific Stream Power (D84) < 2.44
high power
low power
Yes No
0.20
= 110 n
0.26
=42
W_L - % Agri < 13.4%
Yes
0.34
= 14 n
0.24
= 31 No
R_R - Riparian Canopy < 52.3%
low agri
low canopy
0.14
= 15 n
0.21
= 95
Yes No
R_G - Width/Depth < 5.1
15 sites with fewest weedy
0.43
= 5 n
0.30
= 9
Yes No
V_G - Hlsp Connectivity < 8.4
5 sites with most weedy
deep
channels
entrenched

10. Disturbance Tolerance (Model R2 = 0.68)
Reach Scale
Watershed Scale
Valley Scale
Filters
0.23
= 197 n
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0 10 20 30 40 50 60 70 80 90
100
Weedy Species
Number of Sites
Proportion of Assemblage
X = 0.23
0.22
= 152 n
Yes No
0.27
= 45
W_G - Specific Stream Power (D84) < 2.44
high power
low power
Yes No
0.20
= 110 n
0.26
=42
W_L - % Agri < 13.4%
Yes
0.34
= 14 n
0.24
= 31 No
R_R - Riparian Canopy < 52.3%
low agri
high agri
low canopy
0.14
= 15 n
0.21
= 95
Yes No
R_G - Width/Depth < 5.1
15 sites with fewest weedy
0.24
= 36 n
0.37
= 6
Yes No
V_L - % Agri < 1.0%
0.43
= 5 n
0.30
= 9
Yes No
V_G - Hlsp Connectivity < 8.4
5 sites with most weedy
deep
channels
high agri
entrenched
Context matters!

11. Filters High Weediness Low Weediness High Weediness Reach Scale
Watershed Scale
Valley Scale
Filters
Yes No
[1W, 1V, 3R]
0.22
= 152 n
0.20
= 110
0.26
=42
0.14
= 15
0.21
= 95
0.24
= 36
0.37
= 6
[5W]
[1W, 2V, 2R]
0.23
= 197
[4W, 1V]
0.27
= 45
0.34
= 14
0.43
= 5
0.30
= 9
[4W, 1R]
= 31
R_R - Riparian Canopy < 52.3%
V_L - % Agri < 1.0%
W_L - % Agri < 13.4%
R_G - Width/Depth < 5.1
V_G - Hlsp Connectivity < 8.4
W_G - Specific Stream Power (D84) < 2.44
Relatively deep channel
Low Disturbance
Low Weediness
Low % Agriculture
Low Disturbance
High Weediness
High % Agriculture
Low Riparian Canopy
High Disturbance
Low Floodplain
connectivity
High Weediness

12. Models of Community Structure in Streams
Intermediate Disturbance Hypothesis
disturbance
diversity
Habitat Template Model
Patch Dynamics Model

13. Patch Dynamics Model [Townsend, CR. 1989. J.No.Amer.Benthol.Soc.]
Patchwork of habitat with different disturbance histories
Stream organisms are very mobile and colonize quickly
 adjacent patches may have very different fauna
 over many patches, there’s a kind of mosaic equilibrium with a “predictable” assemblage (at the scale of say, a riffle)
Community structure reflects an interplay of biotic and abiotic factors, depending on the degree of spatial and temporal heterogeneity of the system.
Temporal heterogeneity (disturbance) sets population sizes and regulates competition
Spatial heterogeneity (habitat structure) provides refugia, and sets habitat diversity for niche segregation
higher diversity possible when
disturbance intermediate
habitat heterogeneous

14. Habitat comprised of two axes - spatial and temporal heterogeneity
Niche control
Competition dominates (community response to removal of Glossosoma by parasite Cougourdella ? (Kohler & Wiley 1997)
Dominance control
Competitive replacement sequence following disturbance “reset” (Hydropsyche and Simulium - Hemphill & Cooper 1983)
Founder control
Priority effect (Cladophora and Leucotrichia - Hart 1992)
Mobility control
Weedy species (habitat template studies, e.g., Scarsbrook & Townsend 1993; Richards et al. 1997)
Phased succession
All patches undergo similar successional sequence due to synchronized disturbance in homogeneous environment