ecology reflection
Alyssa Johnson
F18Lecture8PopulationDistributionAbundance.pptxPopulation Distribution and Abundance
Lecture 8∙ September 27, 2018
ecological systems form a hierarchy
Overview of ecology
What characteristics allow the Echinacea to survive, grow, and reproduce in the environment of the prairie grasslands of central North America?
individual
ecological systems form a hierarchy
Overview of ecology
Is the population of this species increasing, decreasing, or remaining relatively constant from year to year?
population
A group of individuals of a single species inhabiting a specific area
How does the environment affect the growth, survival, reproduction, distribution, and abundance of species?
ecology of populations
Overview of population ecology
Saving endangered species
Controlling pest populations
Managing fish and game populations
Controlling disease epidemics
Human population growth
Applications of studying the ecology of populations
Overview of population ecology
New unit: Population Ecology
Population Distribution & Abundance
Life Histories
Population Dynamics
Population Growth
New unit: Population Ecology
Literature Comprehension Quiz (Oct. 9)
Guzzo et al. 2017 PNAS
“Behavioral responses to annual temperature variation alter the dominant energy pathway, growth, and condition of a cold-water predator”
Problem Sets (Oct. 4, Oct. 9)
Reflections (Oct. 11)
Exam (Oct. 16)
10 stages of reading a scientific paper
Optimism (“After all, you’ve been reading words for decades.”)
Fear (“Uh … I don’t think all of these are words.”)
Regret
Corner-cutting
Bafflement (“Why was the average sentence 40 words long? Why did the authors use the word “characterize” five times?”)
Distraction (“How would your life change if you owned a bread maker? You’d have to buy yeast. Is yeast expensive? ”)
Realization that 15 minutes have gone by and you haven’t progressed to the next sentence
Determination
Rage
Genuine contemplation of a career in the humanities
http://www.sciencemag.org/careers/2016/01/how-read-scientific-paper
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How to read a scientific paper
This may take a while!
“Nothing makes you feel stupid quite like reading a scientific journal article”
Don’t stress over the abstract, let the introduction be your guide
The introduction should provide the following information:
Identify the big questions of the field and why they are important
Summarize what has been done already, and what questions remain unanswered
Can you distinguish between the big question and the specific question?
What is the hypothesis the authors are trying to test? What are the predictions of this hypothesis that they will test with their experimental design?
Write these down
Describe the general approach the authors plan to use to answer these outstanding questions
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How to read a scientific paper
Hypotheses vs predictions
Hypothesis is generalizable
Predictions follow directly from each hypothesis
If that were true then...
Directly testable from the experimental design
Observation - The last three times I had orange juice for breakfast before an exam, I made an 'A' on the exam.
Hypothesis – Drinking orange juice prior to an exam improves performance.
Predictions -
In a class of students, orange juice drinkers will have higher exam scores than non-orange juice drinkers.
People who do poorly on exams will improve their scores if they start drinking orange juice.
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How to read a scientific paper
Hypotheses vs predictions
Hypothesis is generalizable
Predictions follow directly from each hypothesis
If that were true then...
Directly testable from the experimental design
Practice
Observation - My allergies are worse after I dust my house.
Observation - Grass grows faster in July than in August. Observation - Thin candles burn faster than fat candles
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How to read a scientific paper
Some journals place the methods at the end; it may be useful to refer to them as you read the results
You may also need to reference the supplementary materials online
Chart out the results, and map the methods to each result
This will help you determine if the methods were appropriate or where there may have been experimental biases
You may go back and forth quite a bit as you read through these two sections
Pay attention to sample size, effect size, and statistical measures
Some of this can be best evaluated from the figures
“significant” is a precise statistical term that indicates an observed phenomena is statistically unlikely to be due to chance
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How to read a scientific paper
Spend a minute or two thinking about what the results mean to you, in terms of the original hypothesis
Read the discussion with a skeptic’s eye
Do you agree with the authors’ interpretations of the results?
Do the results support the hypothesis/conclusions?
Are there any alternative explanations for the observed results?
Based on the findings, what do you think is the next step? What questions remain unanswered? What do the results of this study suggest would be most interesting for follow-up study?
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How to read a scientific paper
Tips from grad students, post-docs, profs:
http://www.sciencemag.org/careers/2016/03/how-seriously-read-scientific-paper
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New unit: Population Ecology
Population Distribution & Abundance
Life Histories
Population Dynamics
Population Growth
today’s objectives
Interpret population distributions in light of fundamental and realized niches
Describe the factors that influence distributions of individuals in populations on large and small scales
Understand how ecologists measure abundance and density and the factors that cause variation in these
Distribution
Density
Spatial pattern
Abundance
Age distribution
Birth and death rate
Immigration and emigration rate
Rate of growth
Characteristics of populations
Overview of population ecology
Distribution
Density
Spatial pattern
Abundance
Age distribution
Birth and death rate
Immigration and emigration rate
Rate of growth
Characteristics of populations
Overview of population ecology
Individuals within populations have evolved physiological, anatomical, and behavioral characteristics to compensate for environmental variation
Compensating for environmental variation is metabolically costly
This poses limits on the distribution of species
distribution of species
distribution
The distribution of a species is related to its niche
The niche summarizes the environmental factors that influence growth, survival, and reproduction of a species.
A species’ niche consists of all the factors necessary for its existence
distribution
This space is multidimensional
The distribution of a species is related to its niche
The fundamental niche is the total range of physical environmental conditions that are suitable for existence, in the absence of interactions with other species
The realized niche describes the fraction of the fundamental niche that is actually occupied by a species
The difference between the fundamental niche and the realized niche is usually the result of biotic interactions
Changes near the range boundaries are barriers to further range expansion – one or more environmental variables are beyond the species’ limit of tolerance
distribution
The distribution of a species is related to its niche
The fundamental niche is the total range of physical environmental conditions that are suitable for existence, in the absence of interactions with other species
The realized niche describes the fraction of the fundamental niche that is actually occupied by a species
The difference between the fundamental niche and the realized niche is usually the result of biotic interactions
Changes near the range boundaries are barriers to further range expansion – one or more environmental variables are beyond the species’ limit of tolerance
distribution
The distribution of a species is related to its niche
The fundamental niche is the total range of physical environmental conditions that are suitable for existence, in the absence of interactions with other species
The realized niche describes the fraction of the fundamental niche that is actually occupied by a species
The difference between the fundamental niche and the realized niche is usually the result of biotic interactions
Changes near the range boundaries are barriers to further range expansion – one or more environmental variables are beyond the species’ limit of tolerance
distribution
The distribution of a species is related to its niche
The fundamental niche is the total range of physical environmental conditions that are suitable for existence, in the absence of interactions with other species
The realized niche describes the fraction of the fundamental niche that is actually occupied by a species
The difference between the fundamental niche and the realized niche is usually the result of biotic interactions
Changes near the range boundaries are barriers to further range expansion – one or more environmental variables are beyond the species’ limit of tolerance
distribution
A species fundamental niche is related to the physical limits of the environment
distribution
Geographic range
M. giganteus
M. fuliginosus
The effect of climate might be indirect – through the effect of climate on food, water, and habitat
A species fundamental niche is related to the physical limits of the environment
distribution
Example- Tiger beetle – Cicindela longilabris
240 species of Tiger beetle in N.A.
Often colored; defensive odors; prefer
sandy habitats
A species fundamental niche is related to the physical limits of the environment
distribution
Example- Tiger beetle – Cicindela longilabris
240 species of Tiger beetle in N.A.
Often colored; defensive odors; prefer
sandy habitats
Physiological differences across
wide geographic range?
-or-
Limited by environment in similar
way across wide range?
A species fundamental niche is related to the physical limits of the environment
distribution
Example- Tiger beetle – Cicindela longilabris
240 species of Tiger beetle in N.A.
Often colored; defensive odors; prefer
sandy habitats
Similar temperature
requirements across range
A species fundamental niche is related to the physical limits of the environment
distribution
Beetles probably could not disperse across these lower elevation distances
A species fundamental niche is related to the physical limits of the environment
distribution
Example- Tiger beetle – Cicindela longilabris
240 species of Tiger beetle in N.A.
Often colored; defensive odors; prefer
sandy habitats
Physiological differences across
wide geographic range?
-or-
Limited by environment in similar
way across wide range?
How does the range of barnacles in the intertidal zone relate to the fundamental niche and the realized niche?
distribution
Heat tolerance curves
Heat tolerance is NOT limiting the lower limits of the species distributions
How does the range of barnacles in the intertidal zone relate to the fundamental niche and the realized niche?
distribution
Heat tolerance curves
The upper (vertical) boundaries of the range reflect the fundamental niche and the lower (vertical) boundaries of the range reflect the realized niche.
The upper (vertical) boundaries of the range reflect the realized niche and the lower (vertical) boundaries of the range reflect the fundamental niche.
Both the upper and lower boundaries of the range reflect the fundamental niche.
Both the upper and lower boundaries of the range reflect the realized niche.
How does the range of barnacles in the intertidal zone relate to the fundamental niche and the realized niche?
distribution
Heat tolerance curves
The upper (vertical) boundaries of the range reflect the fundamental niche and the lower (vertical) boundaries of the range reflect the realized niche.
The upper (vertical) boundaries of the range reflect the realized niche and the lower (vertical) boundaries of the range reflect the fundamental niche.
Both the upper and lower boundaries of the range reflect the fundamental niche.
Both the upper and lower boundaries of the range reflect the realized niche.
The distribution of a species is related to its niche
The 20th C was the warmest century in the last 1 million years
Temperatures this century are an average 0.2oC above the mean temperature of the last 500 years
The most rapid warming occurred during the final 30 years of the 20th C
What is likely to happen to fundamental niches as global temperatures increase?
Meta-analysis of 1,700 species Shifts in niche space (average 6.1 km shift toward the poles per decade)
Higher latitude or higher elevation
distribution
The distribution of a species is related to its niche
The 20th C was the warmest century in the last 1 million years
Temperatures this century are an average 0.2oC above the mean temperature of the last 500 years
The most rapid warming occurred during the final 30 years of the 20th C
What is likely to happen to fundamental niches as global temperatures increase?
Meta-analysis of 1,700 species Shifts in niche space (average 6.1 km shift toward the poles per decade)
Higher latitude or higher elevation
distribution
The distribution of a species is related to its niche
Meta-analysis of 1,700 species
Shifts in niche space (average 6.1 km shift toward the poles per decade)
Higher latitude or higher elevation
distribution
What controls the distribution of organisms at small scales (within populations)?
Spatial pattern
Dispersion –
Random
Regular (even)
Clumped
What controls the distribution of organisms at small scale?
Spatial pattern
Three basic patterns:
Random: equal chance of being anywhere
Resources often distributed uniformly
Frequent, random pattern of disturbance
Regular: uniformly spaced
Exclusive use of areas (e.g., territoriality)
Individuals avoid one another
Clumped: unequal chance of being anywhere
Mutual attraction between individuals
Patchy resource distribution
Case study: Distribution of stingless bee colonies
Stingless bees
Don’t sting, but bite
Nest in trees in colonies with > 10,000 workers
Use pheromones to communicate
Some species are highly aggressive, others are not
Spatial pattern
Case study: Distribution of stingless bee colonies
Steve Hubbell and Leslie Johnson 1977
Observed that aggressive species usually forage in groups while non-aggressive species feed singly on widely distributed flowers
Hypothesized that behavior would influence the distribution of stingless bee nests
Surveyed the distribution of stingless bee nests in a tropical dry forest in Costa Rica
Spatial pattern
Case study: Distribution of stingless bee colonies
Steve Hubbell and Leslie Johnson 1977
Observed that aggressive species usually forage in groups while non-aggressive species feed singly on widely distributed flowers
Hypothesized that behavior would influence the distribution of stingless bee nests
Surveyed the distribution of stingless bee nests in a tropical dry forest in Costa Rica
What did they predict about the distribution of nests in aggressive species?
Random
Regular
Clumped
Spatial pattern
Case study: Distribution of stingless bee colonies
Steve Hubbell and Leslie Johnson 1977
Observed that aggressive species usually forage in groups while non-aggressive species feed singly on widely distributed flowers
Hypothesized that behavior would influence the distribution of stingless bee nests
Surveyed the distribution of stingless bee nests in a tropical dry forest in Costa Rica
What did they predict about the distribution of nests in aggressive species?
Random
Regular
Clumped
Spatial pattern
Case study: Distribution of stingless bee colonies
Steve Hubbell and Leslie Johnson 1977
Surveyed the distribution of stingless bee nests in a tropical dry forest in Costa Rica
Spatial pattern
Case study: Distribution of stingless bee colonies
Steve Hubbell and Leslie Johnson 1977
Surveyed the distribution of stingless bee nests in a tropical dry forest in Costa Rica
Spatial pattern
The aggressive species has uniformly distributed nests
The non-aggressive species has randomly distributed nests
Spatial pattern
Creosote bush in Mojave Desert
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Figure 9.9
Case study: distribution of creosote bushes
Spatial pattern
Case study: distribution of creosote bushes
Spatial pattern
How could you test this hypothesis?
Seeds germinate at safe sites
Seeds not dispersed from parent areas
Asexual reproduction
How are individuals distributed on a larger scale, across environmental variation?
Spatial pattern
Abundance = the total number of individuals of a species present in a specified area
Density = # individuals
area
Measuring abundance & density
abundance & density
N = Number of animals in the population
m = Number of animals marked on the first visit
K = Number of animals captured on the second visit
r = Number of recaptured animals that were marked
Measuring abundance & density
MARK-RECAPTURE TECNIQUES
Capture and mark a subset of animals and release, then return at a later time to recapture
r/K = m/N
Assumes: random distribution; no mark effect; no mortality; no migration
abundance & density
How are individuals distributed on a larger scale, across environmental variation?
Spatial pattern
Most species show a clumped distribution, whether they range over a large or small geographic area
American crow
Fish crow
Which factors influence species abundance and density?
Niche characteristics
Conditions toward the edge of the range may lead to physiological stress, which could influence dispersal, habitat selection, and reproductive fitness
abundance & density
Which factors influence species abundance and density?
Body size
John Damuth 1981
307 species of herbivorous mammals
abundance & density
Which factors influence species abundance and density?
What does this figure show about the relative population densities of mammals and birds?
Birds and mammals live at similar population densities
Birds live at higher population densities than equally sized mammals
Birds live at lower population densities than equally sized mammals
abundance & density
Body mass (kg)
Which factors influence species abundance and density?
What does this figure show about the relative population densities of mammals and birds?
Birds and mammals live at similar population densities
Birds live at higher population densities than equally sized mammals
Birds live at lower population densities than equally sized mammals
abundance & density
Which factors influence species abundance and density?
abundance & density
Geographic Range
Habitat Tolerance
Local population size
today’s objectives
Interpret population distributions in light of fundamental and realized niches
Describe the factors that influence distributions of individuals in populations on large and small scales
Understand how ecologists measure abundance and density and the factors that cause variation in these
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Tiger beetle confined to cool environments
Figure 9.3
9-2 Source: Schultz, Quinlan, and Hadley 1992
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Tiger beetle confined to cool environments
Figure 9.3
9-2 Source: Schultz, Quinlan, and Hadley 1992
