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Module 4 - Bio1007 - Notes
From Molecules to Ecosystems (University of Sydney)
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Module 4
Understand the links between morphology, physiology and behaviour
Appreciate ecological and evolutionary significance of behaviour
Understand various behavioural strategies to obtain food, avoid being food, and for reproduction
Appreciate the science behind our knowledge and understanding of behaviour
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Behaviour
o Classically, about animals
o Coping mechanism = 1. Morphology + 2. Physiology + 3. Behaviour
 Behaviour: part of how organism respond to the biotic and abiotic environment
o E.g. carnivores differ from herbivores
 In skull morphology, guts, gut flora, liver enzymes, metabolism
 In behaviours: foraging strategies, social behaviour, communication
o E.g. Gelada baboon foraging behaviour is linked to its:
 Morphology (teeth, guts)
 Physiology (capacity to digest plant cell wall in grass)
 Social behaviour (group size, conflict between feeding, safety, mates)
 Eats the right kinds of food in the right amounts
o Effect of behaviour on fitness
 Fitness: an individual’s relative contribution to the next generation’s gene pool
 E.g. plant-insect interactions
 Insect herbivores consumer vegetative parts of plants
 Insects pollinate ~2/3 of all plants; often with food rewards
 Together with morphology and physiology – natural selection acts on behaviour
 Hence, many behaviours are adaptive
o Ecologically significant because it
 Links individuals and their behaviour
 Affects demographics (population levels outcomes)
 Affects interactions among species (community level outcomes)
o Evolutionarily significant because it
 Has some genetic basis (i.e. nature vs nurture)?
 Affects fitness
 Can be selected (benefits > costs)
o How do we know?
 Observations: inter and intra-specific comparisons
 Manipulative experiments that test hypotheses
Behaviour in relation to:
o Abiotic environment: lizard cooling feet on hot sand by raising limbs
o Biotic environment: foraging, win/choosing mates, escaping/defending
Key aspects of behaviour (1. Obtaining food 2. Avoid becoming food 3. Reproduce)
1. Obtaining food
o Foraging strategies are linked with morphology and physiology
 Ambush predators: camouflage to increase probability of prey encounter
 Active predators: agile and fast to increase probability of prey encounter
o Huge variety of foraging strategies defined by:
 What they eat: herbivore, insectivore, carnivore, omnivore etc.
 How they get it: ambush or active
 Diet breadth: specialist  generalist
o Common feature of all foraging strategies: non-random  individuals make foraging choice  undertake it to
maximise nutrition
 Optimal foraging theory
 Modelled which food items to eat in a non-depleting environment
 Predicts foragers should maximise net rate of food intake
 Marginal value theorem
 Modelled when to leave a food patch in a depleting environment
 Predicts that foragers should leave food patches when capture/harvest rate at patch <
average/harvest rate
o Patch has marginal value compared to the surroundings
 Foraging ecology tests such predictions about foraging behaviour
 Net rate model: maximises the quantity of food foraged
 Efficiency model: maximises the energy output required per unit food
o Note: optimal foraging theory focuses on efficiency of energy gain
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 Sometimes foraging only for nutrients
 Behaviours also depends on the nourishment of the forager too
 But most foragers are also prey
o We should expect that:
 Foraging strategies to be linked to predator avoidance strategies
 A trade-off between food and fear
2. Avoid becoming food
o The dead don’t reproduce, therefore being eaten = ultimate fitness cost
 Strategies to reduce predation risk  relevant to most of food chain
o Anti-predator strategies include:
 Run away
 Groups
 Hide
 Act costly (act dangerous, mimic unpalatable or toxic organisms)
 Be costly (sequester toxic compounds, have spines)
 Feed in safe places or times (vegetation cover, new moon)
o Costs of anti-predator strategies
 Missed opportunities to forage in better locations  due to far away from vegetation cover
 Competition for food and social aggression  groupings
o For anti-predator strategies to evolve benefits > costs
3. Reproduce
o No reproduction  fitness = 0 as genes are not passed on
o Trade-off costs and benefits
o Courtship and mating
 Relevant to sexual reproduction
 Involves: male-male competition and female choice
 Results in non-random mating  sexual selection
o E.g. peacock tail
 High costs of such tail: energy and maintenance  risk of predation
 Benefits  access to mates
 Darwin hypothesised peacock tail arises from natural selection
o Sexual selection:
 Intrasexual selection (usually for males and species where the males are larger than females):
competition between genders  facilitates access to mates
 Intersexual selection: mate choice  once provided the choice
o Parental care
 Benefits: increases survivability and growth of offspring  fitness
 Costs: missed opportunities to reproduce again
 In some species, offspring stay and help parents rear more offspring
All organisms show a foraging trade-off between food and fear
Plant behaviour
o Leaves and stems
 Grow towards light
 Respond to their environment by moving
o Roots
 Grow along chemical gradients towards nutrients
 Respond to their environment by moving
o Plant behaviour? Why not!
 Different time frame (plants move slowly)
 Different way of moving (plants move parts of themselves
(modular))
 Similar: all living organisms respond to their environment
What is behaviour?
o Interaction with environment (abiotic and biotic)
o Involves stimulus: response
o Sensory? (do you need a brain, or even nerves, or senses to behave?)
o Semantics?
o Does it matter?
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Be able to describe and understand exponential and logistic models of population growth
Define instantaneous growth rates in discrete and continuous exponential growth models
Become familiar with demographic rates and how they are measured
Understand what a stage/age structure model is
Understand what a spatially structured population is
Understand the principles and implementation of population viability analysis
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Groups: multiple organisms (can be singular or multiple species) occupying a common space
o Can be ephemeral or consistent
o Can be social (positive or negative), indirect (sharing common resource) or accidental (random chance)
Populations: a number of organisms of the same species in a defined geographical area
o Definition encounters issues for highly migratory groups of individuals
o Composition and structure are influenced by life history, mobility and habitat
o Properties of populations include:
 Number of individuals or population size
 Area they occupy
 Age structure
 Sex ratio
o Play a central role in our understanding of the factors that shape and drive the diversity of life
Populations are essential for:
o Ecology:
 Distribution and abundance of individuals
 Density
o Evolution:
 Populations of organisms evolve, not individuals
 Gene flow
o Conservation and management:
 Invasive species
 Defined threat status of taxa
 Translocations and restoration
Groups vs Populations
o Dynamics: populations are more cohesive through time
Individuals: populations consist of a number of individuals that grow, survive and reproduce  individuals may be
unitary or modular
o Unitary:
 Develop from zygote: genetically distinct
 Form to determinate
 Development and growth predictable
o Modular:
 Grow by addition of modules (e.g. leaves or lengths of stems): genetically identical (clones)
 Individuals are highly variable in the number of
modules (e.g. some plants, aquatic invertebrates)
 Modular ‘individuals are often difficult to count
 Look at the percentage of space covered
Importance of population biology
o Understand temporal dynamics of populations
o Understand spatial distribution of populations
o Natural selection occurs within populations
Population growth
o Populations change in numbers over time
o Change can be positive or negative
o Rate (r): change/unit time
 Populations grow at different rates
Demographic rates
o Variables that drive changes in population size: (first 4 affect the population numbers, last 3 affect rates)
 Birth
 Death
 Emigration (number leaving population)
 Immigration (number entering population)
 Growth (individual)
 Age at maturity
 Sex ratio
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Birth and death
o Fundamental to population growth  balance of the birth versus death
o Measured in changes of individuals per yea
o Balance between additions (births) and losses (deaths) determines growth rates
o Inherent to all types of population growth models
Population growth in ‘closed’ systems
o The population growth rate is the change in numbers of individuals over time
o Where there is no emigration or immigration, the population is ‘closed’ e.g. isolated areas, islands, mountain
tops
o Nt = number of individuals in the population at time t
 Nt+1 = Nt + Births – Deaths
 Number next year (t+1) = Number (N) this year (t) after accounting for changes in births and deaths
Exponential growth
o Geometric growth is exponential: a population’s per capita growth remains the same irrespective of population
size; thus, populations grow faster as they get bigger
o Dynamic over time depends on life history of organism
 Discrete: reproduction occurs periodically
 Continuous: reproductions occur year-round
Estimating birth rates
o Common methods:
 Histology of reproductive organs
 Capture/counting of fertilised gametes
 Counting of newly born individuals
Resource limited growth
o Population growth is often resource limited (e.g. food, space, water, nesting sites etc.)
o Numbers cannot increase without bound
Estimating death rates (mortality)
o Common methods
 Tagging
 Follow individuals (for sessile organisms)
 Probability based (for more motile organisms)
 Changes in size structure (how many organisms caught are young versus old)
o Very challenging – how can you know for sure an individual has died unless you see it happen or sample the
entire population?
Population growth in ‘open’ systems
o The population growth rate is the change in numbers of individuals over time
o Nt = number of individuals in the population at time (t)
o If the individuals move in and out of the populations then it is ‘open’
 Nt+1= Nt + Births – Deaths + immigrants – emigrants
Estimating demographic rates
o Relatively easy for individuals which do not move
o Movement
 Tagging and recapture
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 Physical
 GPS
 Radio telemetry
 Acoustic
 Genetics
 Genetic similarity occurs with only very low levels of interbreeding between populations
o i.e. individuals move far
o if they are genetically distinct, it means that the demographic is enclosed
 Genetic differences = no movement between populations
 Genetic analysis of microsatellites
Spatially structured populations
o Metapopulations
 Local populations, but individuals move
 Demographic rates vary spatially
 Large-scales dynamics dependent on local demographics and connectivity
 Can prevent global extinction
o Glanville Fritillary butterfly
 Periodic local extinctions
 Recolonization from nearby populations
 Metapopulation level extinction prevented
o Mayfly
 Larval stages mature in local pools
 Adults disperse between pools
 Mortality variable from pool to pool
 Some pools are sources (low mortality) while others are sinks (high mortality)
Estimating population size
o Common tools
 Counts
 Visual
 Auditory
 Acoustic
 Mark-release-recapture (MRR)
 Estimates the total population size from a sample proportion of a mobile species
 Use the proportion of recaptures to estimate whole population size
 Assumptions often are hard to satisfy:
o Closed population (no immigration, no emigration)
o All individuals equally likely to be marked
o Marked individuals do not lose their mark
 Technique has been used successfully on many animals, including whales, lizards, small
animals
Demographic rates: growth (individual), age at maturity, sex ratio
o Estimating growth and age
 Trees: tree rings  dendrochronology
 Perennial plants: rings in the tap root
 Mammals: counting rings in teeth e.g. grey-headed flying fox
 Fish: otoliths (ears which provide fish balance)
Understanding age and size-structured population dynamics
o Age and/or size of an individual affects:
 Fecundity (probability of giving birth)
 Survival
o Treating all members of a population as identical  unrepresentative of natural population structure
o Imbalanced initial age structure  age and number cycles
o Life tables: show survivorship probability at each age
o Long-term studies: key to understanding population dynamics
Australia’s human population dynamics
o Changes in human population size: mostly due to behavioural changes
o Economists need to know the future age structure to plan: more infrastructure
o The current trend: ageing population
o Growth rate of many western countries:
 Below replacement rate
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 Population numbers will level out then fall
Extinction: loss of all populations of a species
o Processes of chance that contribute to an extinction event
 Genetic stochasticity (small populations)
 Demographic stochasticity (random nature of births and deaths)
 Environmental stochasticity (variability)
 Catastrophes (cyclones, epidemics, fire)
 Human impacts (habitat loss, fragmentation, over-exploitation, hunting, pollution, introduction of new
pest species, other environmental changes e.g. climate change)
Population viability analysis (PVA)
o Toll used to model population dynamics over time
o Uses basic population data
o Includes environmental variation in these values
o Can change values to reflect human impact
o Key information needed:
 Population size/carrying capacity (K)
 Fecundity
 Mortality: adults and juveniles
 Inter-annual variation in parameters
Model sensitivity
o A tool which enables you to enter all data significant to measure population dynamics
o PVA only as good as the data
o Test the robustness of conclusions using sensitivity analysis of parameters based on known or hypothesised
variance in the data used to estimate the parameters
o Fundamental to PVA
o Allows estimation of what could occur if certain changes occur
Summary
o Populations are groups of organisms of the same species in a defined area
o Biotic and abiotic factors can influence the processes of population change: birth, death, immigration and
emigration
o Populations can be ‘closed’ if they primarily change only by birth and death processes or ‘open’ if immigration
and emigration are also important in affecting changes in numbers
o Populations may grow exponentially at first but as resources become limiting, growth slows until they may
reach the carrying capacity  such growth is typically described by a logistic curve
o The age/stage structure of a population affects population growth
o Population viability analysis is a toll that can be used to determine the long-term vulnerability of species to
extinction under a variety of scenarios
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Define the biological species concept and interspecific hybrids
Provide arguments in the debate about the species problem
Describe what is known about the number of species and how this varies globally, by region and by group
Use methods for counting and estimation of the number of species
Variation within species
 Groups within a species can be defined as being of a taxon hierarchically lower than a species
 In zoology only, the subspecies is used
 In botany the variety, subvariety, and form are used
 In conservation biology, the concept of evolutionary significant units (ESU) is used, which may define either species or
smaller distinct population segments
 In horticulture there are cultivars
 There are also breeds of domesticated animals such as dogs, cats, cattle, sheep
What do we mean by a species?
 Definitions: in biology, a species is one of the basic units of biological classification and a taxonomic rank
o Can be genotypically similar but completely different species
 A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring
 Biological species concept
o Ernst Mayr’s definition of a species as: ‘groups of actually or potentially interbreeding natural populations,
which are reproductively isolated from other such groups’
Limitations of the biological species concept
 This concept may not be relevant to organisms that are capable of asexual reproduction (e.g. many types of bacteria)
 If the definition of a species requires that two individuals are capable of interbreeding, then an organism that does not
interbreed is outside of that definition
o Fossils
o Clonal species
o Asexual species
 Organisms may also breed beyond the notional definition of species
o Interspecific hybrids
o Ring species
Other species concepts
 Ecological species (lives in the same space)
 Biological/isolation species
 Genetic species (look at the genetic differences)
 Cohesion species
 Evolutionary significant unit (ESU) (preserve their species separate from other species)
 Phenetic species
 Microspecies
 Recognition species
 Mate-recognition species
Interspecific hybrids
 Another difficulty that arises when defining the term species is that some species are capable of forming hybrids
Hybridisation – why does it occur?
 1) breakdown of reproductive isolating barriers which usually prevent gene flow between closely related species
o Separation of geographical location or intrinsically genetically different
 2) potential causes of hybridisation in Lomatia include:
Habitat disturbance
Species in closer proximity
Secondary contact
Increased migration distances (pollinator change, or dispersal) – through vectors
Altered phenology
Leading to overlap in flowering time (and pollen transfer)
Altered genetics
Breakdown in the pollen incompatibility system
 3) potential evolutionary outcomes:
o Sterile (F1)
o Speciation – new species
o Enhancing variation
Ring species
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Ring species arises when a parental population expands
around an area of unsuitable habitat in such a way that
when the two fronts meet they behave as distinct species
while still being connected through a series of intergrading
populations
o Further away you get – the lesser possibility of
interbreeding
Species problem – review of ideas
 The difficulty of defining species is known as the species
problem
 Differing measures are often used, such as similarity of DNA,
morphology or ecological niche
 Presence of specific locally adapted traits may further subdivide species into ‘infraspecific taxa’ such as subspecies
 Many organisms do not conform to the reproductively isolated criteria
 Not possible to test this for fossil taxa
Vascular Plant Flora of Australia
Native Species
15 638
Species – how many species are there?
Naturalised Species
1 952
Number of species – Mammals NSW
Total Species
17 590
Monotremes
2
Presumed Extinct
83
Marsupials
46
Described Species
19 324
Rodents
17
% world described
6.9%
Bats
37
Estimated species
~21 645
Total
102
Percentage endemic
91.8%
Species numbers
 Insects comprised about 57% of all named species
 Beetles comprised 25%
 Most non-insects have probably been discovered and described
o Most insects never will
Methods of counting the amount of insect species in a tropical rain forest
1) Method: counting the number of beetles on one tree species
 Knockdown method: insecticide fog in the canopy, insects die and fall onto collecting devices
 Sample: 19 individuals of a leguminous tree
o Luehea seemannii at different seasons
 Results: 9000 beetles from 1200 beetle species
 Comparison: 2800 species of Arthropods from the canopies of 10 trees belonging to 5 species in the Bornean rainforest
 Based on extrapolations:
o 13.5% of beetles live only on this one tree species, there are ~50,000 species of tropical trees,
o Implies 8.1 million species specialising on single tree species
 + 2.7 million beetle species live on >1 tree species
 = 10.8 million species of canopy beetles
o If beetles are 40% of all tropical arthropod species
o Implies 27 million arthropod species in the tropics
 + 3 million temperate species
 = 30 million arthropod species in the world today
2)
 Arthropods: number of arthropod species which is ~6.8 million
 Cryptic species: mean number of cryptic species for each morphologically defined arthropod species
o Multiplied the mean number of cryptic species per described species per study (5.9 rounded to 6)
o By the projected number of arthropod species based on morphological criteria (~6.8 million)
o This yielded our baseline number of arthropod species (40.8 million)
 Mites: next, we assumed that each of these arthropod species has (on average) at least one associated mite species
 Nematodes: we then assumed on average of one nematode species per arthropod species
o We added these estimates for arthropods and nematodes for a total of 163.2 million animal species
 Plants: 0.340 million; Fungi: 165.5 million; Protists: 163.2 million
 Bacteria: we estimated that each animal species hosts an average of 10.7 unique bacterial species, yielding 1.75 billion
bacterial species in total (163.2 million x 10.7 = 2.238 billion species)
Using the higher taxonomic classification of species to estimate number of species
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The assignment of species to phylum, class, order, family and genus follows a consistent and predictable pattern from
which the total number of species in a taxonomic group can be estimated
The method predicts:
o ~8.7 million (+/- 1.3 million SE) eukaryotic species globally, with
o ~2.2 million (+/- 0.18 million SE) of these marine
After 250 years of taxonomic classification and > 1.2 million species
o 86% of existing species on Earth and
o 91% of species in the ocean still await description
Species are only one component of biodiversity
 Biological diversity is the variety of life on Earth
 Number, relative abundance and genetic diversity of organisms on Earth
 Components
o Genetic diversity (e.g. heterozygosity, number of alleles)
o Species diversity
o Community diversity
o Landscape diversity
Species problem: measuring biodiversity
 Species richness = number of species
 Species turnover = difference between samples
 Evenness = equitability of individual abundance among species
 Diversity indices (many types)
 Many ecological communities are made up of a few common species
and many rare species
 Rank abundance curves can be used to compare community composition
o Steeper slope indicates that the commoner species are a greater total proportion of the community
o Number of dots = amounts of species
o Vertical axis looks at the amount of that particular species
 Measures using a constant area size in all areas i.e. 0.1 ha in rainforests in Asia and Australia
 The amount of species which are found depends on how hard we look
o Need a strong and consistent searching design
Types of community diversity
Alpha
Alpha diversity is the number of species within a
chosen are or community
Similar species richness
Local diversity
Beta
Beta diversity is the difference in species between
areas or communities
High species turnover
Species turnover
Gamma
Gamma diversity is the diversity of a landscape of
all areas combined
Regional diversity
Species diversity indices
 Diversity within communities, alpha-diversity is quantified
with diversity indices
 Combines number of species and relative abundance of
individuals within species
 Many types that emphasis either common or rare species
and have different types of bias
 Comparisons should be done using the same index
 Tow commonly used indices
o Simpson’s index
o Shannon-Weiner index
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Review how organisms get their energy
Describe the concept of trophic levels
Explain how energy flows within ecosystems
Describe food chains and food webs (‘eat or be eaten’)
Describe the various types of ecological interactions among species
Link ecological interactions to the flow of energy through trophic levels using herbivory as an example
Appreciate the science behind ecological knowledge and understanding
How do organisms get energy/nutrients?
 Autotrophs
o Producers
o Make it themselves (synthesise organic
from inorganic compounds)
o Green plants, phytoplankton, algae
(+chemosynthetic bacteria)
 Heterotrophs
o Consumers, degraders, decomposers
o Get it from others
o Animals
Food chains
 Describe the energy flow between organisms among trophic levels
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However, in real life, it is often much more complicated
Often quite short (3-5 links)
o Due to:
 Hypothesis 1) diminishing energy transfer between levels (90% is lost as heat)  energy hypothesis
 Evidence shows that the more energy available at the autotrophic level, the longer the chain
 Hypothesis 2) the dynamic stability hypothesis
 Longer food chains less stable due to fluctuations at low trophic levels magnify at high levels
o Therefore, the top predators more likely to go extinct
 Therefore, higher environmental stability results in longer food chain length
 Hypotheses are not mutually exclusive
Food web
 Describe more complex interactions
 Involve ecological interactions
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Ecological interactions
 Are exchanges and flow of energy and matter
o Within and between trophic levels  intimately linked with trophic ecology
 Include:
o Mutualism: 2 organisms in close association, both benefit (+, +) e.g. clown fish and anemone
 Obligated and facultative mutualisms
o Competition: (-, -)
o Predation: (+, -) e.g. herbivory, carnivory, parasitism
 Herbivory: plants are not great food for animals however,
 Herbivory is the biggest interaction on the planet
 Important for individuals
 Can affect populations and communities
 Can affect ecosystem processes
 Herbivory fundamentals
 Tissue loss by herbivores = animal allocation to reproduction in plants (how much could they
have reproduced if they had not been eaten?)
 Herbivores eat the high-quality plant tissue (so % impact much greater than tissue loss
suggests)
 Plants have defences against herbivores (herbivores exert selective pressure)
o Commensalism: (+, 0)
o Amensalism: (0, -)  stepping on insects
o No interaction: (0, 0)
Plant-Herbivore Interactions (+,-)
 Examples of herbivory and population ecology
o Effects of leaf selection on population dynamics of an insect
herbivore
 Eating plant material  digestion  conversion to ‘insect’ material  insect performance and
survival and fecundity  population growth
 Require plant material that maximises reproductivity and survivability
o Tussock moth larval survival depends on growth conditions of plants:
 Aspen: best under high CO2 + low light, worst under high CO2 + high light and survivability of caterpillar
changes from 80%  20%
 Examples of herbivory and community ecology
o Effects on populations  community level responses
 Moose browsing  decrease downy birch
 Decreased canopy cover  decreased arthropod biomass
 Decreased arthropod biomass  decreased tit fledglings
 Herbivory and ecosystem processes
o The preferences of the moose can affect plant communities
 E.g. if they prefer to eat willow and aspen trees, it will allow the spruce tree population to increase
 Herbivory at the ecosystem level
o Carbon cycle
 At the trophic level requires decomposers (soil) >> herbivores
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Communities as a definable entity
Communities in ecology
 Communities: two or (usually) more species that occur together in space and time
 In addition to co-occurring, community members interact with each other as an ecological unit
 Sometimes taken to be just vegetation, but should include all biota that occur together
 Assemblages: Less well defined, but can be taken simply as a group of species that live together with no assumptions
made about how or whether they interact with each other
Ecotones
 Gradual transitions the norm rather than the abrupt ‘hard’ edges (though the terrestrial – marine transition can be seen
as an example of ‘hard’ edge)
 Ecotones – usually a transitional area between two different communities, such as woodland and heath
Communities over time
 Change in composition a constant in nature
 Local colonisations and extinctions
 Classic models driven by succession (recently – mainly caused by human created)
 Predictable patterns of change in response to a disturbance
 New communities are being assembled by human activity
 New communities often homogeneous in many parts of the world
 Assembling communities of the same organism  biotic homogenisation
Succession
Succession – general
 Tree falls down in forest, creating light gap
 Light unsuitable for certain species (esp. shade-tolerant), creates high quality environment for other species
 Changes in species composition and abundance, growth rates in lower canopy stratum
 Dominant species etc. in system change over time
 Various biogeochemical processes associated with the presence of certain species also change
 New dominants move in
 Equivalent changes often seen with animals, fungi
Succession of plant species on abandoned fields in North Carolina:
 Pioneer species consist of variety of annual plants
 Followed by communities of perennials and grasses, shrubs, softwood trees and shrubs, and finally hardwood trees and
shrubs
 Succession takes about 120 years to go from pioneer stage to the climax community
Types of succession
 Primary succession
o Bare area without soil e.g. sand-dune
 Secondary succession
o In habitat modified by other species – something already there to build one e.g. agricultural field
Models of succession
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Facilitation
o Early arriving species make environment more favourable for
later species
Tolerance
o Neither negative nor positive interactions between early and
late species
Inhibition
o Early species inhibit later species
Plant species’ roles in succession
Pioneer species
 Grow in sun
 Fix nitrogen
 Good dispersal
 Small seeds
 Rapid growth
 Short generation time
 Poor competitors (focus on reproduction)
Climax species
 Shade tolerant
 Slow growth
 Long-lived
 Good competitors (less focus on competitors)
Climax community – final composition remains the same
 The ‘final’ community in a successful series
 Self-perpetuating, no replacement
Competition and its effects on communities
Competition: role in succession
 Limited resources
o One organism deprives another organism of a resource (the resources are sometimes, but not always, in short
supply): exploitation and interference competition
 Intraspecific competition
o Density dependence
o Population regulation
 Interspecific competition
o Competitive exclusion
o Niche differentiation
Competition and successional niches: rock platforms
 Range and distribution of species
 Tide shifts
 Changing conditions
 Competition and limiting resources
 Extent of interactions: barnacles
 Removal and transplant experiments
 Chthamalus was able to extend its range down in the absence of Balanus, therefore, mortality not caused by
submergence but by interspecific competition
 Balanus not affected by presence of Chthamalus
 Balanus competes by smothering, undercutting or crushing competition
Role of disturbance in community structure
Intermediate Disturbance
 Observations of storms on tropical rainforests and coral reefs
 Does disturbance promote diversity?
 Patchy mosaic of disturbance creates highest diversity  intermediate
disturbance hypothesis
Resilience and succession
 Resilience: how long before a community returns to an ‘equilibrium’ after
disturbance
 What objective and non-arbitrary criteria for determining pre- and post-disturbance conditions do we have
 Australia often uses the ‘before 1788’ criterion to define pre-disturbance conditions – but there are many problems with
this
 Active area of debate
Ecosystems
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The community of living organisms considered in conjunction with the abiotic components of their environment,
interacting as a system
Can be measured as ecosystem productivity per different environments
Ecosystems and atmosphere – surface linkages
Case study – trophic cascades and carbon cycles
The science behind the ecological knowledge and understanding
Biogeochemical cycles
 Energy flows through the biosphere
 Materials are recycled
 Ecosystem productivity is controlled by the efficiency of recycling as well as by energy available
 Materials transported in the atmosphere (water, carbon, nitrogen and sulfur)  global cycles (usually gaseous)
 Phosphorous, potassium, calcium and magnesium move through soil  local ecosystem cycles
Productivity in ecosystems may change through time
 Young ecosystems have more actively growing tissue, but older systems have more biomass
 If resources are limited, regeneration of the original ecosystem may be impossible – cleared rainforest may revert to
open grassland
Upwelling
 Marine systems are relatively unproductive
 Nutrients (especially nitrogen and phosphorous) tend to accumulate at great depths and are unavailable to
phytoplankton
 Major fishing grounds in upwelling zones where nutrients are forced up
The water cycle
 ~ 97% of water on earth is in the oceans
 Processes of convection, precipitation, transpiration and respiration move water around the cycle
 ~3% of total water is relatively inaccessible, in icecaps, glaciers and as deep groundwater
 Within the scale of local ecosystems, water behaves more like energy because it effectively flows through and is not
recycled – water which rains is not necessarily from local sources
Australian conditions
 2/3rds of mainland Australia is desert
 Rainfall is highly variable
 Desert ecosystems productive in pulses when rain falls, or from utilisation of reserves (seeds, lignotubers) at other times
 Consumers must:
o Adopt a ‘pulse (rain) and reserve’ patter e.g. grasshoppers
o Eat reserves of other organisms e.g. seed eaters
o Adopt opportunistic feeding habits
The Carbon cycle
 Most carbon is locked up in earth’s rocks as carbonate (and as fossil fuels)
 The most active pool is carbon dioxide (0.04% of the atmosphere and increasing)
 CO2 is withdrawn by photosynthesis and replaced during respiration
 Large amounts of CO2 are dissolved in the ocean
 Burning of fossil fuels returns CO2 to the atmosphere faster than it can be recycled  contributing to global warming
The Nitrogen cycle
 Abundant in atmosphere, 78%
 Plants cannot absorb atmospheric nitrogen
 Absorbed as ammonium or nitrate after fixation of nitrogen by symbiotic bacteria, or in soil solution
 Denitrifying bacteria convert nitrate back to gaseous nitrogen
 Electrical storms also fix nitrogen
 Nitrogen becomes limiting if microbial activity is inhibited
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Rural dieback and nitrogen
 Tree dieback results from long or repeated periods of sublethal stress
 Effects of increased stocking rates, growing exotic pasture species, adding fertilisers and land-clearing combine to cause
rural dieback
 Insect damage to leaves is worse where soil fertility is high
 Stock congregate under few remaining shade trees, both damaging saplings and enriching the soil
Phosphorous cycle
 Essential to all life, in ATP
 Not common in earth’s crust or in atmosphere
 Taken up plants as phosphate from sparingly soluble soil storage pool
 Australia flor are well adapted to low P, and efficient at recycling phosphorus
 Symbiosis between plant roots and mycorrhizal fungi enhances the phosphorus supply
Old soils and the Sydney Basin
 Old systems are often limited by phosphorous owing to slow inputs
 Plants native to Australia have had millions of years in which to adapt to nutrient-poor soils  relatively slow growing
 Consequences of nutrient inputs
o Faster plant growth
o Facilitation of invasive species
Trophic Cascade
 Powerful indirect interactions that can control entire ecosystems, usually when predators in a food web suppress the
abundance or alter the behaviour of their prey, releasing the next
lower trophic level from predation
 Case study: otters
o Mainly eat sea urchins
o Boost kelp (primary producer, locks up a ton of CO2 and
supports ecosystem) populations
 Transports CO2 to the deep ocean or locks it up
within the fronds
o However, may be predated on by killer whales or humans
 When predated, kelp presence is non-existent as
sea urchins predate on kelp
 Lack of presence of kelp reduces productivity
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Review how human activities affect the ecology of natural systems
Understand the impacts of pollution and how it affects the ecology of natural systems
Understand how pollutants move pollutants move into natural systems
Understand the ecological impacts of habitat fragmentation
Understand the ecological impacts of climate change
Appreciate the science behind this ecological knowledge and understanding
Toxic inputs
 Pesticides
 Manufacturing
 Industrial accidents
 Chemical spills
 Atmospheric pollution
 Plastics
 Nanoparticles
Bioaccumulation
 Occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost 
accumulation
 Persistent (don’t usually breakdown) and mobile (move through different ecosystems
 Accumulation occurs in body tissues
 Particularly in higher predators at the top of food chains and webs
 Diverse group of toxins introduce in 1940-50s for different reasons i.e. pesticides
 Many used because they work quickly
o 2,40D and 2,4,5-T (herbicides)
o DDT, dieldrin and lindane (organochlorine insecticides)
o PCBs (polychlorinated biphenyls, chlorinated organic compounds used as insulation in electrical equipment i.e.
transformers, coolants – very stable)
o Heavy metals (mercury, lead, cadmium)
Impact on human wellbeing – Inuit of North Canada
 PCBs are highly stable
 PCBs found in breast milk of mothers in southern Quebec in the mid 1980s
 Need for a control  what’s in ‘pristine milk’
 Obtained milk from Inuit mothers
 Inuit milk had 5 times the PCB levels (also toxaphene and chlordane)
 Another study found that more than 2/3 of children had unacceptably high levels of PCBs (figure surpassed 95% where
whale consumption was high)
 Older people had higher levels
Effects?
 Children born to women who ate PCB-contaminated fish
 11-year olds exposed to PCBs in the womb had:
o Lower IQ
o Poor memory
o Shortened attention span
o Learning difficulties
 Hostility between indigenous people and researchers
How is it getting there?
 No agriculture/manufacturing in northern Canada
 Inuit use almost every bit of narwhal and beluga whales
taken every year – preference for muktuk (skin and surface
fat) – highest accumulation of PCBs
 Also consume bits of ringed seals (livers), caribou (kidneys) and fish
 Toxins accumulate in certain body parts, particularly fat of these predators
But who’s using it?
 Not the Inuit – PCBs banned in Canada in 1977
 ‘Global distillation’ and ‘global fractionation’ – processes whereby volatile chemicals are transported long distances
 Heavy usage in tropics, where they evaporate from soils, carried on winds (fractionation) and then condense out in the
cold as toxic snow and rain (distillation)
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Systematic transfer from warm to cold
Very slow breakdown in cold climates
Solutions
 Problem transcends borders
 PCBs are now banned worldwide
 Monitoring and regulation
The problems with lead
 Usage of lead shot by shooters is consequently ingested causing organ breakdown
 Modest recovery of the California condor after > 30 years on the brink (22 birds in 1982)
 Intensive captive breeding and medical intervention – requires perpetual, intensive support
 Condors ingest lead after feeding on the carcasses of animals that hunters have shot down, leading to chronic lead
poisoning
 2008 California ban on the use of lead shot where the birds were being reintroduced
 But feather and blood samples from trapped birds found no discernible difference in lead levels before and after the ban
 Many have dangerous levels of lead in their bodies
 Lead poisoning severely damages birds’ nervous systems and impairs liver and kidney function
 ~20% of wild condors have lead levels requiring costly treatments
Oil impacts on coastal communities
 The old wisdom: acute mortality through short-term toxic exposure to oil deposited on shore accounts for the only
important losses of shoreline plants and invertebrates
 The new wisdom: clean-up attempts can be as damaging as the oil itself, with impacts recurring as long as clean-up
(chemical and physical methods) continues
o Strong pervasive biological interactions in rocky intertidal and kelp forest communities contribute to cascades
of delayed, indirect impacts and expand the scope of damages well beyond the initial direct losses and thereby
also delay recoveries
o Need for development of ecosystem-based toxicology; monitoring may be needed for > 100 years
Habitat fragmentation: classic ideas from theory of island biogeography
 Habitat loss is one of the major contributors to biodiversity loss
 Fragment size and isolation are primary drivers of diversity
 Edge effects are prevalent
 Shape matters
 Connectivity and corridors enhance landscapes
 Role of the matrix – hospitable or not?
Two effects of fragmentation
 Biomass collapse – Amazonian fragments (edge patches will decrease in biomass)
o Experimentally fragmented landscape created between 1980-86
o Patches of land isolated by clearing/burning to create pastures
o Rate of biomass loss greater near the forest edges
o Decline in above ground biomass before and after fragmentation (from subset of edge sites)
 High tree mortality
 No recruitment of new trees
o Why?
 Microclimatic factors strongly affected on edges: wind and hydrology
 Increase in woody vines (lianas) near edges doesn’t compensate for loss of trees
 Ecological meltdown – predator-free fragments
o Differential losses and susceptibility to invasion – does loss of higher predator’s release prey from regulation?
o Top-down/bottom up regulation in ecology
o Construction of a dam in Venezuela created large lake, with hundreds of former hilltops becoming islands
o Small and medium islands did not support > 75% of vertebrates from mainland and control sites; mostly
predators lost (predators require space to find prey)
o Remaining vertebrates are invert predators, seed predators or herbivores
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Tend to be hyperabundant
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Losing predators – and processes
o Predators of vertebrates are absent, and densities of rodents, howler monkeys, iguanas, and leaf-cutter ants
are 10 to 100 times greater than on the nearby mainland, suggesting that predators normally limit them
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Densities of seedlings and saplings of canopy trees are severely reduced on herbivore-affected islands: forest
cannot recover
Evidence of a trophic cascade unleashed in the absence of top-down regulation
Types of changes expected and now observed from climate change
Animals and Plants
Hydrology and glaciers
 Range shifts (latitudinal or altitudinal)
 Glacier shrinkage
 Abundance changes
 Permafrost thawing
 Change in growing season length
 Later freeze and earlier break up of river and lake ice
 Earlier flowering, emergence of insects, migration and
egg-laying birds
 Morphology shifts (e.g. body and egg sizes)
The cold hard truth?
 Background – artic sea ice shrinking
 Opportunities for new fisheries
 Loss of habitat for many species
 Species favouring ice-dominated systems with shallow benthic communities (e.g. bottom-feeding ducks, walrus) will
diminish and be replaced by systems dominated by pelagic fish
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The extinction crisis
 IUCN Red list has 20,000 species at risk of extinction
o 25% of mammals, 41% of amphibians
 Rate of extinction 10-100,000 times higher than background rates
o Should be only ~1 species every few years
 Australia’s recent mammal extinctions
o Lost ~33 species in the last 200 years
 ~80 species extinct worldwide since 1500 AD
 ~60 worldwide in the last 200 years
o Non-flying mammals in the ‘critical weight range’ (CWR) have suffered most
 CWR = 35g to 5.5 kg – arid zone species suffered most
 One forest species has become extinct (Christmas Island pipistrelle)
 Overall: >30% of nation’s mammals are extinct or threatened
o Most had disappeared by the 1930s
 Western NSW: case study of mammal loss
o 325,000 km2
o 1788: 72 species of native mammals
o 1993: 45 species remain, 33 which are secure
o Faunal losses: 41% of marsupials, 65% rodents
o One species moved back in 2015
Paradigms for conservation biology
 Aims of Conservation Biology
o To describe problems and understand processes driving species number depreciation
o To predict impacts of threats
o To develop solutions
o Ultimately: stop more species/communities/ecological process going extinct
 Paradigms of conservation biology
o Small population – small population increases risk of population loss
 The effect of small numbers on a population’s persistence
 i.e. stochastic influences (demographic and environmental, genetic drift, inbreeding depression)
 How or why it is small is not the issue
o Declining population – on a trajectory towards complete population loss
 Why the population has declined to low numbers, what might be causing it and what might be
causing it and how to reverse the decline
 Diagnose the causes of declines and treat them
The ‘evil quartet’; alien species, overhunting, habitat loss, co-extinction
 Note: factors are driven by human over-population which underpins it all
 Alien Species
o Australia has introduced 56 species of vertebrates
o Annual economic and biodiversity cost estimated at:
 ~$800 million to $1 billion managing pest animals
 $4 billion managing weeds (direct control and lost production)
o New Zealand has more alien plant species (>24,000) than native ones (6,700)
o New megafauna
 Introduced 100-200 years ago with Europeans
 Cattle, sheep, goats, pigs, buffalo, donkeys, deer, horses, camels now all feral
 Many are major pests
o New microfauna
 Cats, rats, mice arrived with early explorers
 Rabbits, hare, foxes, cane toads and others released
o Invasion – getting here
 Deliberate introductions
 Human traffic
 Native invaders
o Tens rule
 1/10 of plant and animal species brought into a region will escape to appear in the wild
 1/10 of those escaped species will become naturalised
 1/10 of these will become invasive
o Invasive species tend to have characteristics that:
 Maximise or enable high reproduction
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 Enable great ecological dispersal
 Enable species to be greatly ecologically flexible
 Traits of pioneer species in succession
o Impacts of introduced animals
 Pest animals were usually deliberately introduced
 Feral animals: fox, rabbit, cats, pigs, goats, donkeys, camels, water buffalo, mosquito fish, cane toads
 Feral species in Australia: 20 mammals, 25 birds, several amphibians, 30 freshwater fish, 1000s of
invertebrates
o Case study of invasive species: red fox
 Preys on everything
 Competes with carnivorous marsupials
 Local fauna naïve to it
 Linked to 12 extinctions of mammals and threats to: 48 mammals, 14 birds, 12 reptiles, 2 amphibians
 Distribution limited and facilitated by rabbit distribution
 Suppressed by the dingo over large areas
o Huge potential for reinvasion
 Placement of species placed behind enclosures
 Measure the visitations to artificial breeches in the fence
 Requires consistent maintenance to prevent reinvasion
 Pest animals tend to constantly try to reinvade the enclosure
Overhunting
o Humans over-exploiting wildlife :
 Bounties placed on brush-tailed rock-wallabies
 Numerous kangaroos killed based of QLD government decree 1877-1930
 As food/resources e.g. fisheries management, bushmeat and wild meat
 Overexploitation risks higher in data-deficient systems
Habitat loss and the extinction debt
o Habitat destruction is the major cause of species extinction
o Island biogeographic theory suggests that
 Reducing habitat area to 10% of its former extent will eventually
cause ~50% of species dependent on natural habitat to disappear
 These predictions are not always matched by observations
o Debt reflects the future ecological cost of current habitat destruction –
extinctions occur generations after fragmentation
o Moderate habitat destruction is predicted to cause time-delayed but
inevitable, deterministic extinctions
Co-extinction
o Critical ecosystem functions lost when species are lost
 Haast’s eagle in NZ went extinct after its main prey, moa, were hunted to extinction
 Hawaiian ‘hibiscus’ close to extinction because of loss of honeyeater pollinators due to alien species
 Cassowaries are only vector of large rainforest fruits – their decline puts these fruits at risk
 Loss of engineer species from Australia’s rangelands
o Parasites and hosts
 Passenger pigeon – once most numerous birds on the plant >5 billion birds
 Hunted to extinction in USA
 Co-extinction of 2 species of bird louse
Prediction the future better – impacts and extinction risk
What can we do? Restoration ecology
What can you do?
 Experiments are key to identifying processes driving extinction and allowing management and future predictions to be
made
 Introduced predators decrease prey numbers twice as much compared to native predators
 Fox control and native mammal (black-footed rock wallaby) conservation
o Removing foxes from the habitats using 1080 poison causes numbers of the wallaby to increase
o Usage of 1080 poison in WA kills foxes but not native species as 1080 is part of a native plant
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Solutions: modelling
o Modelling population dynamics to predict impacts and identify management options
o Population viability analysis
 Most effective at comparing management options – looks at the most ideal intervention and their
impact
 Minimum viable population size – should be large for long-term persistence
 Data hungry process, bit very helpful and effective
Solutions: legislation
o Part of federal and state legislation
o List of species, populations, communities  provides recovery plans
o Identify critical habitat
o List threatening processes  threat abatement plans
Solutions: other evidence-based approaches
o Smart ecological solutions
 Evidence-based (evidence-informed)
 Addressing causal factors rather than patterns
o Integrated pest management
 Interrelationships between pests means we can’t just control one or
others will benefit: need good ecological understanding
o Restoration ecology
Restoration – resetting the clock
o Restoring ecosystems to some pre-impact or reference state
o Enhancing habitat quality
o Restoring ecosystem functions via reintroductions
o E.g. restoring bauxite mines – goals:
 Establish self-sustaining jarrah forest ecosystem
 Vegetation community which is floristically and structurally similar to the nearly undisturbed forest
 Faunal assemblage recolonising over time
Does revegetation foster the recovery of the landscape?
o Structural attributes: returning with less floral diversity
o Seed dispersal by ants: function returned quicker  not linked to assemblage composition but identity of key
functional groups
o Insect pollination: replacement of native pollinators, similar services in different way
o Beetle assemblages: field of dreams supported
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