This week:

Final 4 presentations - two on Tuesday and two on Thursday…

No readings!

Today:

Your Principles… My Principles and Macroecology

Where is there activity in the search for laws (or generalities) in ecology today?

Macroecology =

A 2-step process: (1) find large-scale patterns(2) determine the underpinning mechanism(s) for those patterns

-- McGill (2003)

Promise of Macroecology:

While much ecological research is narrowly focused and experimental, providing detailed information that cannot be used to generalize from one ecological community or time period to another, macroecology draws on data from many disciplines to create a less detailed but much broader picture with greater potential for generalization. Integrating data from ecology, systematics, evolutionary biology, paleobiology, and biogeography, macroecology provides a richer, more complete understanding of patterns of life on earth over time.

Searching for the “meaning of the mean” in the variance…Or the underpinning laws…

Ernest et al (2003)

Body mass and production – organism based

Linking organisms and population density

Enquist et al. (1998)

Enquist et al (2003)

Ecosystem flux vs. temperature

Identifying fundamental allocation relationships

Plant biologists have long held the opinion that much idiosyncratic and site-specific variation exists in biomass allocation both within and across plant taxa. Taxon and site-specific variation in biomass allocation is well-known in response to differential selection for adaptations to different environmental conditions (e.g., species adapted to deserts tend to have reduced leaf mass with respect to root mass.

Nevertheless, when viewed across a large range of plant sizes, the about 10-fold variation in biomass allocation is slight as compared with the striking invariance observed (and predicted) for the scaling exponents of leaf, shoot, and root mass across an impressive nine orders of magnitude from diverse communities differing in latitude and elevation. 

--Enquist and Niklas (2002)

Recent seminar indicated that only 10% of the facts taught in lecture courses are retained…and we should teach concepts or principles instead. This means one should have a good idea of what the central concepts/principles of Ecology are.

If someone where to ask you to list the most important principles (rules, generalities, concepts) in Ecology, what would you consider them to be?

Assignment:

• What are the core principles of ecology that underpin and create the patterns and processes we see?

Principle: the ultimate source, origin or cause of something, a fundamental truth, an essential element, constituent, or quality, especially one that produces a specific effect

Break into groups of 4 – turn these in (legibly written) at the end of class… (include names of people in each group)

ECOL 505 Foundational Principles and Concepts – 2010 Class

•Physical laws must be obeyed, Allometric scaling

•Resources & Energy are limiting, Resources increase productivityEnergy loss occurs through trophic levelsEcological systems are open and influenced by outside factorsEnergy flows and Nutrients cycle

•Predator-prey, Source – Sink population effects, Carrying capacityConnectivity, food webs

•Evolution, Natural selection is importantSpecies life history is importantHistory (evolutionary and ecological) and context is important

•Organisms interact Humans are a keystone speciesIntermediate DisturbanceThe niche, competition Biodiversity increases stability and resilience

•Scale is important, Smaller scales provide mechanisms for larger scalesPatterns and processes vary with latitude, Island biogeography

•Stochasticity is ever-present, Change is constant

•Stoichiometry is important

“Others”

Ecology is a REAL science

Well….it depends

Ken Buck is not an ecologist…

My seven principles - Motivation:

• Instead of attempting to explain away the idiosyncratic nature of ecology and its poor predictability, we should try to identify those fundamental principles of ecological systems that lead to these exact attributes, yet provide overall limits to the behavior of ecological systems…

• These principles don’t have to be unique to ecology, but in total they will be uniquely important to understanding ecological systems.

• Define Principle as: Fundamental truth as the basis of reasoning or action

Principle 1. Ecological patterns and processes are underpinned by physical laws – Ecology as a higher order science follows the laws of those disciplines that provide its foundation. Thus, fundamental laws of physics and chemistry constrain all ecological systems and processes.

For example, the thermal, physical and chemical limits of the functioning of membranes and proteins provide the mechanisms that determine potential boundaries for the distribution of species.

Failure to recognize this can be…well…embarrassing…

Principle 2. Ecological systems are open but resources are finite– Ecological systems require energy and certain essential resources. They are energetically open, but resources are both finite and subject to consumption.

Open systems allow for an increase in order (information) to accrue through time in ecological systems while not violating thermodynamic laws.

That resources are finite and consumable provides the basis for well-known energetic (trophic) constraints, species interactions, and coupled with the abiotic limits in Principle 1, defines a fundamental concept in ecology – the niche.

This Principle also dictates rates and patterns of population growth and regulation

Principle 3. Biotic and biogeochemical processes are coupled through ecological stoichiometry – organisms are characterized and constrained by a common set of chemical requirements and are composed of similar ratios of essential elements.

Species differences in their ability to acquire and compete for these elements determine where a particular portion of the biota occurs and the degree to which the biota will alter biogeochemical cycles.

EnvironmentBiota

Principle 4. Evolutionary history constrains the ecological present and future – Evolutionary history and its product, the current genetic structure of the biota, influences and constrains contemporary ecological phenomenon and hence, the ecological future.

Given sufficient time and similar selective backgrounds, convergent evolution may operate to permit equivalent ecological patterns and processes, but well-known evolutionary mechanisms (bottlenecks, founder effects, drift) will leave a legacy imprint on contemporary ecological pattern and process.

Principle 5. Ecological history and context further increase the contingent nature of ecological systems – Antecedent biotic or abiotic events (including geologic) affect contemporary ecological systems and processes.

The strength of this contingency is not directly proportional to the time since the event occurred since the influence of some events may be muted with time, whereas others are reinforced.

Principle 6. All aspects of ecology are scale dependent – Ecological systems, processes and interactions, and the physio-chemical rules that govern them, are scale dependent at the level of the observer, the pattern observed and the process (mechanism) of interest.

Not unique to ecology, but this principle must be recognized and appreciated.

Principle 7. Ecology is the science of interactions and multiple causal factors– In almost all cases, the drivers of ecological pattern and process are multiple, interactive and probabilistic – both temporally and spatially.

Ecological systems and processes are affected by multiple and concurrent abiotic and biotic (including human) factors that are inherently interactive, variable in nature and not always normally distributed.

Further, the statistical distributions of these factors do not directly relate to ecological responses so that, for example, rare events can be disproportionately important in ecological systems, and uncommon organisms can have disproportionate influences (keystone species, ecosystem engineers, etc.).

A B

Independentvariable

Underpinning law

EvolutionaryHistory

EcologicalHistory

AbioticFactors

BioticFactors C

D

E

F

H

G

The “essence of ecology” is to understand this complexity and be as predictive as possible…

These principles provide an explanatory basis for the most essential and consistent features of the behavior of ecological systems.

Few are unique but in total these seven principles are important to remember if we are to truly understand ecological systems.

The product of these principles is that predictability and generality in ecology will be limited to specific scales and will be contingent on the past as well as the statistical distribution of contemporary variables. (In other words, if unpredictable disturbance regimes are a key driver, then ecological forecasts will have to reflect this)

Predictability will only emerge when scale is specified and appropriate, the evolutionary and ecological past can be controlled or accounted for, and the statistical distributions of key driving variables are known.

And that is just the way it is!