Stream Ecology (NR 280)
Topic 10 – Lotic Communities
Review of community elements
Large-scale influences on species diversity
What controls community structure?
Do species prefer one niche over another?
How does community structure change over time?
Community structure and ecosystem function
Using community structure for management
Building blocks of community structure
in stream communities
• Autotrophic species
– Algae
– Bryophytes
– Macrophytes
• Micro-heterotrophic species
– Taxonomic groups (e.g., Pseudomonads)
– Functional biogeochemical groups (e.g. denitrifiers, sulfate reducers)
• Benthic macroinvertebrate species
– Taxonomic groups (e.g., EPT)
– Functional feeding groups (e.g., grazer, shredder, etc.)
• Fish species
– Taxonomic groups (e.g. Cyprinids, Salmonids)
– Fish guilds (e.g., bottom feeder, algivore, piscivore)
• Stream-reliant species
– Salamanders, birds, bears
Interactions within community structure
that define stream communities
• Food and Feeder
– Primary production and grazing/herbivory
– Secondary production and consumption
– Predation and cannibalism
• Functional relationships
– Competition
– Mutualism/Commensalism
– Special species interactions
Expressing community structure
Connectance food web - Broadstone Stream, UK
Schmid-Araya et al. (2002) in Allan and Castillo (2007)
Expressing Strength of Connection
Example: Energy Flux Food Web
Ogeechee River, Georgia
Benke and Wallace (1997) in Allan and Castillo (2007)
Interesting questions to consider
• What is a community?
• Why don’t we see the same species
everywhere?
• What factors influence the structure of
biological communities in stream
ecosystems?
• What is the influence of community
structure on ecosystem function?
Stream Ecology (NR 280)
Topic 10 – Lotic Communities
Review of community elements
Large-scale influences on species diversity
What controls community structure?
Do species prefer one niche over another?
How does community structure change over time?
Community structure and ecosystem function
Using community structure for management
Species Area Curves
Two different senses of this concept
• Sense 1: Diversity = f(area available)
– A metric of the environment
– A indicator of regional diversity
• Sense 2: Richness = f(area sampled)
– A metric of sampling effort
– A indicator of local diversity
Species Area Relationships
Larger areas typically support more species
49 coastal streams
on US East Coast
to Gulf of Mexico.
Note log-log axes
and linear form.
Sepkowski and Rex (1974) in Allan and Castillo (2007)
Remember that this relationship has
the familiar log-linear form
S = c Az
S = number of species
c = constant
A = area
z = scaling factor (constant)
Log(S) = Log(cAz)
Log(S) = Log(c) + Log(Az)
Log(S) = Log(c) + z(Log(A))
Y = a + bX
Power function = Log-Linear function
Relationship
between
basin area
and fish
diversity in
world rivers
Mekong River Commission
Species Area Curves
Two different senses of this concept
• Sense 1: Diversity = f(area available)
– A metric of the environment
– A indicator of regional diversity
• Sense 2: Richness = f(area sampled)
– A metric of sampling effort
– A indicator of local richness
Local species area (sampling effort)
The species area relationship is shown from the rate at which species are added to
collections as sampling effort (shown by number samples) increases. In this
example, samples of macroinvertebrates have been collected from four habitats (2
pools, 2 riffles) in a Hong Kong stream. Note that the species accumulation curve
does not level off in Riffle #1 because new, rare species are encountered even
after 30 samples have been taken.
Mekong River Commission
Species by abundance
Are all species equally abundant?
Broadstone River
United Kingdom
24 years of sampling
Woodward et al. (2002) in Allan and Castillo (2007)
Special Species Interactions
Unionid mussels and fish
Watters (1992)
Special Species Interactions
Unionid mussels and fish
Unionid mussels require specific fish hosts to
transport the larval form of the mussel (glochidia).
Watters (1992)
Stream Ecology (NR 280)
Topic 10 – Lotic Communities
Review of community elements
Large-scale influences on species diversity
What controls community structure?
Do species prefer one niche over another?
How does community structure change over time?
Community structure and ecosystem function
Using community structure for management
What controls community structure?
The deterministic view
• Communities are non-random assemblages of
species with predictable and repeatable
structural patterns
• Communities are relatively stable in the face of
“ordinary” environmental stresses
• Community structure is the outcome of
interactions between habitat characteristics and
species preferences
What controls community structure?
The non-deterministic view
• The specific structure of a community is dependent
on a random sample of species from the regional
pool that are able to survive and reproduce in the
local environment
• Hubbel’s (2001) “Neutral model”: Species are
interchangeable. The habitat offers a template
(deterministic) that is then randomly occupied by
species (non-deterministic)
Key theories about stream community structure
These are not mutually exclusive
• Habitat Template influences: physical characteristics of
the habitat determine what species can exist in a place;
diverse habitats have diverse community structure
• Disturbance influences: environmental disturbance (e.g.
flow, temperature) favors some species and does not
favor others
• Niche influences: structure is determined by interplay of
biotic interactions (e.g. predation, herbivory,
competition) and abiotic forces (habitat, disturbance)
Some general observations
• Community structure is often persistent over years
• The same species are often dominant at a location,
year after year
But…
• High temporal variation in key environmental variables
may mask persistence and dominance
• Persistence and dominance are indicative of
deterministic factors but don’t explain them
Stream Ecology (NR 280)
Topic 10 – Lotic Communities
Review of community elements
Large-scale influences on species diversity
What controls community structure?
Do species prefer one niche over another?
How does community structure change over time?
Community structure and ecosystem function
Using community structure for management
Why should individual species prefer
specific habitats?
The concept of species traits
• Species have particular traits that may impose
specific habitat requirements
• Habitats offer specific characteristics that may
favor particular species
Lamouroux et al. (2004)
Example species traits & habitat characteristics
16 of 60 traits used in this study
Lamouroux et al. (2004)
What Lamouroux et al. concluded
• Strong relationship
between species traits
and microhabitat
characteristics
• Consistent relationships at
the reach scale
• Inconsistent relationships
at the basin scale (n=2)
Poff (1997), also Fig 1.5 Allan and Castillo (2007)
General Observation
Local biological diversity is the outcome of
regional species richness interacting with local
environmental conditions and historical events
to define the subset of species that exist at a
given time in a given stream location.
Paraphrased from Allan and Castillo (2007), p. 230
Regional Definition/Local Expression
Fixed
Environmental
Template
Filters; e.g.
Geology
Topography
Insolation
Regional
Species
“Reservoir”
Changing
Environmental
Template
Local
Habitat
Filters; e.g.
Runoff
Climate
Glaciation
Local
Community
Local scale
History (presses and pulses)
State (conditions)
Regional scale
Stream Ecology (NR 280)
Topic 10 – Lotic Communities
Review of community elements
Large-scale influences on species diversity
What controls community structure?
Do species prefer one niche over another?
How does community structure change over time?
Community structure and ecosystem function
Using community structure for management
Streams have different flow regimes
Based on 78 USGS gauging stations
High
Low
How intermittent is the flow?
Not at all
Harsh
Intermittent
Abiotic
Intermittent
Runoff
Abiotic
Perennial Flashy
Low flow predictability
Abiotic
Snow and Rain
Low flow predictability
Seasonally biotic
Perennial runoff
Low flow predictability
Abiotic
Winter rain
Low flow predictability
Seasonally biotic
Mesic groundwater
High flow predictability
Biotic
Snowmelt
High flow predictability
Seasonally biotic
Flood Frequency
High
Low
Intermittent
Flashy
Abiotic
Low
High
Flood Predictability
Modified from Poff and Ward (1989) in Allan and Castillo (2007)
Flow regime, disturbance, & community structure
Disturbance causes short-term change
Insect abundance in a stream
in the Andean foothills after
>25mm storm events
Flecker and Feifarek (1994) in Allan and Castillo (2007)
Recovery following flash flood disturbance
Sycamore Creek, Arizona
Autotrophs
Benthic Macroinvertebrates
Fisher et al. (1982) in Allan and Castillo (2007)
How communities change over time
Long-term factors
• Dispersal – movement of species in space
– Immigration: species moving to a location
– Emigration: species moving from a location
• Speciation – development of species in time
• Biogeography – suitability of species to exist in
a particular space at a particular time
Presses, pulses, and tipping points
• Press
– A steady application of perturbing force
– Climate change, development
– A measure of resistance to change
• Pulse
– A sudden application of a perturbing force
– An accidental spill, Hurricane Irene
– A measure of resilience to change
• Presses and pulses may interact
– Non-linear responses, “surprises”
– Tipping points – permanent changes to a new state
Stream Ecology (NR 280)
Topic 10 – Lotic Communities
Review of community elements
Large-scale influences on species diversity
What controls community structure?
Do species prefer one niche over another?
How does community structure change over time?
Community structure and ecosystem function
Using community structure for management
Interspecific facilitation
Filtration of suspended particles in artificial stream
• 3 filter-feeding larval caddis
fly species
• Feeding alone (open) or with
other 2 species (hatched)
• Dependent variable is per
capita consumption of
suspended matter
Cardinale et al. (2002) in Allan and Castillo (2007)
Interspecific Facilitation
Impacts on decomposition of leaves
High dominance Low dominance
Low evenness
High evenness
36 streams
France Sweden
Low dominance
○
●
High dominance
□
■
Damgles and Malmqvist (2004) in Allan and Castillo (2007)
Removing one species alters ecosystem processing
Atlas of the freshwater fish of Venezuela
Taylor et al. (2006)
Difference
-fish
-fish
Data
Experiment results
Benthic organic carbon
Carbon flux
Heterotrophic respiration (only)
Gross primary production
P:R ratio (actually GPP/CR)
Net ecosystem metabolism
Carbon turnover length
Taylor et al. (2006)
See comments panel for legend
Human impact: smaller fish
(smaller net sizes, not shown)
Stream Ecology (NR 280)
Topic 10 – Lotic Communities
Review of community elements
Large-scale influences on species diversity
What controls community structure?
Do species prefer one niche over another?
How does community structure change over time?
Community structure and ecosystem function
Using community structure for management
Common Benthic Macroinvertebrates
Moderately
Tolerant
Sensitive
(Intolerant)
•
•
•
•
•
•
•
•
Stoneflies
Water Penny Beetles
Mayflies
Dobsonflies
Alderflies
Snipeflies
Mussels
Riffle Beetles
•
•
•
•
•
•
•
•
Damselflies
Dragonflies
Crayfish
Amphipods
Blackflies
Caddisflies
Isopods
Craneflies
Tolerant
(Insensitive)
•
•
•
•
Midgeflies
Worms
Leeches
Pouch Snails
http://www.epa.gov/bioindicators/html/benthosclean.html
Benthic Macroinvertebrates
The “Good” EPT Taxa
The “Poor” taxa
http://www.epa.gov/bioindicators/html/benthosclean.html
Simple guide
(North Carolina)
Macroinvertebrate Index of Biotic Condition
•
•
•
•
•
•
Taxonomic richness
Taxonomic composition
Taxonomic diversity
Feeding groups
Habitats
Pollution tolerance
EPA Wadeable Stream Assessment (2007)
Index of
Biotic
Integrity
Karr (1981) and Karr et al. (1986)
from
EPA-260-R-08-016 (2008)
Response of Sensitive EPT Biota
High-gradient stream reaches
 Non-linear response at ~5% TIA
 No significant response at TIA > 10% (N = 6; p = 0.157)
 % Cobble substrate explained 11% of EPT variance
Watershed TIA
Fitzgerald et al. (2012)
Impacts of
Impervious
Area
Center for Watershed Protection (2003) as noted.