Transcript Document

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…
Body mass and production – organism based
Ernest et al (2003)
Linking organisms and
population density
Enquist et al. (1998)
Ecosystem flux vs. temperature
Enquist et al (2003)
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 sitespecific 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 productivity
Energy loss occurs through trophic levels
Ecological systems are open and influenced by outside factors
Energy flows and Nutrients cycle
• Predator-prey, Source – Sink population effects, Carrying capacity
Connectivity, food webs
• Evolution, Natural selection is important
Species life history is important
History (evolutionary and ecological) and context is important
• Organisms interact
Humans are a keystone species
Intermediate Disturbance
The niche, competition
Biodiversity increases stability and resilience
• Scale is important, Smaller scales provide mechanisms for larger scales
Patterns 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.
Biota
Environment
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.).
D
G
Evolutionary
History
A
Independent
variable
Biotic
Factors
Underpinning law
Ecological
History
Abiotic
Factors
C
B
E
H
F
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!