1. (2) Functional Perspective – based on species traits –IDEA: Characterize the traits of species in the community, rather than the taxonomic identity. –ADVANTAGES: Traits related directly to environmental forces that vary from site to site –Disturbance, temperature, pollution, siltation, etc. Traits can be applied across biogeographic boundaries because they do not depend on species identities, rather functional characteristics –DISADVANTAGES: Being able to describe species in terms of traits that are “sensitive” or directly responsive to environmental factors Important aspects of community structure

2. Some traits for macroinvertebrates: North America: Poff et al. (2006, J. North American Benthological Society) Europe: Table 10.2

3. Some traits for fish: http://www.cnr.vt.edu/fisheries/fishtraits/

4. Habitat Template Model Species traits should vary along environmental gradients Traits that “match” environmental conditions are “selected” for. Southwood (1977) Townsend & Hildrew (1994)

5. Test of Habitat Template Test #1 - Inverts: [Scarsbrook and Townsend 1993] 2 streams in New Zealand #1 stable, high habitat heterogeneity #2 flashy, low habitat heterogeneity Stream #1 Stream #2 SedimentFine to coarseFine gravel/sand Hydrol. Regime"stable""flashy" Disturbance Freq.LH RichnessHL Dominance by mobile mayfly (similar to Baetis)LH Drift rateLH Sedentary taxaHL CPOM/FPOMHL Max. size of mayflyHL

6. Stream #1 Stream #2 SedimentFine to coarseFine gravel/sand Hydrol. Regime"stable""flashy" Disturbance Freq.LH RichnessHL Dominance by mobile mayfly (similar to Baetis)LH Drift rateLH Sedentary taxaHL CPOM/FPOMHL Max. size of mayflyHL Test of Habitat Template Test #1 - Inverts: [Scarsbrook and Townsend 1993] 2 streams in New Zealand #1 stable, high habitat heterogeneity #2 flashy, low habitat heterogeneity

7. Test #2 - Inverts: [Richards et al. 1997] Streams in Great Lakes drainage that differ geologically and thus in “flashiness”

8. Test #2 - Inverts: [Richards et al. 1997] Estimated probability of moderate and high representation of different species traits: Long-lived (merovoltine) species rare in flashy flashier stream sites. Obligate depositional taxa incrase with pool habitats. “Clinger” species (e.g., mayflies) decline with fine sediment. merovoltine taxa Index of flood intensity Obligate depositional taxa Clinger taxa

9. Test #3 - Fish: [Poff & Allan 1995] Streams in Wisconsin and Minnesota that differ in terms of hydrologic variability Ho: Fish communities will vary in species trait composition depending on stream hydrology. 1) Define 2 different community “types” based solely on species traits 2) Define a “gradient” of hydrologic variability among the 34 streams 3) Test Ho. (Community types fall out along gradient of stream stability.) Flashier stream types have fish traits: generalist foragers, generalist habitat, slow water, tolerant of silt

10. Models of Community Structure Predictor variable(s): –habitat structure (spatial heterogeneity) –habitat dynamics (temporal heterogeneity / disturbance) –biotic interactions Response variables (”community structure") –species identities (diversity, richness) –species traits

11. How do biotic and abiotic factors vary in space and time? Basic ecological theory - 1 Habitat Template Concept (Southwood 1977) - species require different attributes ( traits ) depending on habitat stability (disturbance). (Fig. 3) merovoltine taxa Index of flood intensity Examples that we’ve seen:

12. How do biotic and abiotic factors vary in space and time? Basic ecological theory - 2 Intermediate Disturbance Hypothesis (Connell 1978) - species diversity (or richness) varies with disturbance (or habitat stability) disturbance Diversity or Richness Prediction? –Maximum species diversity at intermediate level of natural disturbance. Mechanism? (What explains pattern?) –What “kinds” of species will occur at either end of the disturbance gradient? Differences in competitive ability, tolerance, etc. “r-selected” and “K-selected” species –Evidence for IDH in streams?

13. Test of IDH –Townsend et al. (1997) Sampled invertebrate communities in many sites throughout a river catchment in New Zealand. Sites differed in intensity of bed movement

14. How do biotic and abiotic factors vary in space and time? Patch Dynamics Model (Townsend, 1989, J. No. Amer. Benth. Soc.) - combines Habitat Template and Intermediate Disturbance Basic Premises: (1)Stream is a patchwork of habitat with different disturbance histories (2)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) (3) 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 heterogeneity for niche segregation (4) Higher diversity possible when  disturbance intermediate  habitat heterogeneous Basic ecological theory - 3

15. 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 Habitat comprised of two axes - spatial and temporal heterogeneity

16. disturbance diversity How do streams differ in their disturbance regimes? Where will we expect to see strong biotic interactions?

17. Some issues about disturbance Disturbance is an event that causes mortality(or alters resources) Mortality depends on : –Habitat characteristics (Refugia) Channel morphology / Substrate (mobility) –Taxonomic group: Algae / Inverts / Fish / Riparian vegetation –Traits of species Ability to avoid, for example –Magnitude of event -"little" vs. "lots" of mortality so … Disturbance is –  scale-dependent ! –  context-dependent! (different in different settings)

18. Important distinction: –An individual disturbance is an event; –temporal pattern of events is regime Event vs. Regime (ecological response) (evolutionary adjustment) [some mortality]["adaptation"]

19. Some Questions: Question #1: If disturbance causes mortality, and streams highly disturbed, how do species persist??!! –"Weedy" traits (Fig. 5) High mobility (colonizing) Fast (or asynchronous) life cycles High fecundity –Specific behavior / life history adaptations to avoid disturbance Spatial refuge: –Move to spatial refugia (e.g., Matthaei et al. 2000) –Abetus (water bug) and flash floods Temporal refuge: –Fast development in flashy system (e.g., Gray 1981, Fig. 4) –Time emergence prior to predictable floods (Lytle 2002) Low chance for 50 day development 10 days

20. Question #2 : If disturbance causes mortality, but species avoid disturbance, then is the event really a disturbance? Or are species well “adapted” ? Example: annual predictable disturbances in Rocky Mountain streams. Adaptation or Disturbance? –Under what conditions can "adaptation" occur? Signal is frequent (relative to life span) Signal not TOO extreme (survivors needed!) Signal-to-noise ratio is high (periodic, predictable) –What if disturbance is frequent, yet unpredictable? –Fast development –Asynchronous, multivoltinism (bet hedging)

21. Natural Flow Regime and Evolution Extreme events (floods and droughts) exert primary selective pressure for adaptation, because they often represent sources of mortality. (Lytle & Poff. 2004. Adaptations to natural flow regimes. Trends in Ecology & Evolution) Types of adaptations: Life History, Behavior, Morphology

22. Classification of streamflow “types” (806 unregulated streams in US) Intermittent predictable snowmelt flashy predictable stable GW Perennial unpredictable predictable winter rain Components of Disturbance REGIME Magnitude Frequency Duration Timing Predictability Rate of change in flow Streams can be characterized in these terms. –Poff & Ward (1989, 1990), Poff (1996) – Figs. 11.6, 11.7 text)

23. Allows a priori expectations about structuring processes in communities. > 90 d per year no flow Perennial with high flood frequency, low flood predictability, and high day- to-day variation in Q Perennial with low flood frequency, low flood predictability, and low day- to-day variation in Q Perennial with low flood frequency, high flood predictability, and low day- to-day variation in Q Augusta Creek, MI Fig. 10.6 in text