Overview of Lecture: Ecology: Communities & Ecosystemssee the schedule for reading and watching assignments

Bullet Points: • community ecology• interspecific competition• the Lotka-Volterra model• competitive exclusion• character displacement• predators & parasites• keystone species• the loss of large predators• Spaceship Earth – is tiny and under great stress • local & global biodiversity – why sustain biodiversity?• climate change – the public good & the tragedy of the commons

Don’t forget to complete the MSU online SIRS form:https://sirsonline.msu.edu

Learning Goals:1. Be able to use examples from lecture and/or the text & videos to explain the Lotka-

Volterra competition model and what additional ecological and demographic processes it incorporates beyond the logistic model. Be able to use examples to help explain competitive exclusion. What, in general, tends to lead to coexistence rather than competitive exclusion in competitive interactions

2. Be able to explain the the keystone predator hypothesis and how predators or parasites can increase biodiversity. Use examples from the studies by Rippleet al. and by Estes et al. to help explain why the disruption of trophic cascades that results from the extirpation of top predators creates such concern for the maintenance of biodiversity and ecosystem function.

3. Be able to explain in what sense is the anthropogenic forcing of global climate change similar to the public goods game know as the tragedy of the commons?

Don’t forget to complete the MSU online SIRS form.

Earlier: Unlimited populationsgrow exponentially.

Multispecies communities w/ complex food webs are very complex systems with many positive and negative indirect interactions!ex: “my enemy’s enemy is my friend”

0

1

0 2 4 6 8 10

time t

rel p

op s

ize

N/K

= x

mu=2

mu=3.2

mu=4

r=0.5

Density-dependent regulationof demographic rates (b & d)limits pop growth (λ or r);

if pop growth rate (λ or r) is low, N approaches carrying capacity K;

if pop growth rate is high, dynamics cyclic or chaotic.

A biological community isan assemblage of populations of various species living close enough for potential interaction.

Ecologists define the boundaries of a particular community to fit their research questions. [increasingly, communities are global]

The exponential growth model: dN/dt = N r

How can we add a little more realism to this model

by incorporating Interspecific Competition?

Suppose we can measure the impact of

one individual of species 2 on the pop growth rate of species 1

relative to the impact of one additional individual of species 1?

Call this rate of substitution the interspecific competition coefficient a12(the intraspecific coefficients a11 & a22 are implicitly = 1)

The Lotka-Volterra interspecific competition model:dN1/dt = N1 [r1max (1 - 1 N1/K1 - a12 N2/K1)]

dN2/dt = N2 [r2max (1 - 1 N2/K2 - a21 N1/K2)]

If we do the math we find stable coexistence of both species 1 & 2

ONLY IF a12 < 1 & a21 < 1, meaning: intraspecific comp > interspecific comp,

implying: diff species use resources differently {different niches}.

Otherwise, we expect competitive exclusion of one of the species by the other.

The logistic growth model: dN/dt = N [rmax (1 - N/K)]

incorporates

Intraspecific competitionw/ density-dependent

-FB on growth rate r

When grown in competition,P. aurelia drives P. caudatum

out of the system

A classic illustration is from Gause’s exp’s w/ paramecia (see Fig 39.3)competing for bacteria = food in chemostats (w/ fixed input of food).

When grown separatelyeach species does fine

(note: P. aurelia has smaller r but larger K)

Competitive exclusion is expected from details of L-V competition model,but there is a simple verbal interpretation (from D.Tilman):

Note that P. aurelia has a bigger carrying capacity K than P. caudatum.

This means that each P aurelia can survive & reproduce w/ less resources:((1/KPa)th of the resource base) < ((1/KPc)th of the resource base).

The growing pop of P.aurelia can drive resources below the minimum required for individual P. caudatum to reproduce.

Competitive exclusion is often found in simple lab experimentswhere 2 diff species are forced to scramble for one limiting resource.

(it’s difficult to maintain stable pairs in simple environments w/ exploitation competition).

Prospects for 'competitive exclusion' treatment to control salmonellas and other foodborne pathogens in poultry.

Mead GC. 2000. Veterinary Journal 159:111-123.

My enemy’s enemy is my friend!

Lactobacillus … a competitive exclusion agent against bacterial pathogens in poultry.

La Ragione et al. 2004. Letters in Applied Microbio, 28,197-205.

Lactobacillus as a probiotic for preventing urogenital infections Andreu A Reviews in Medical Microbiology 15 (1): 1-6 JAN 2004 This article discusses the role of Lactobacillus as a probiotic agent

for the maintenance of vaginal microflora and the prevention of urogenital infections. Lactobacillus protects the vagina from colonization by pathogens by ...

blocking their attachment to the vaginal epithelium and producing substances that inhibit their multiplication.

In newly hatched chicks, the rapid establishment of an adult-type intestinal microflora, produces almost immediate resistance to colonization by salmonellas.

Exploitation of the 'competitive exclusion' effect is now an accepted part of the overall strategy by which poultry-associated salmonellas are being controlled in some countries.

There are two possible outcomes of competition between species w/ identical niches: either the less competitive species will be driven to local extinction, or one of the species may evolve to use a different set of resources.

This differentiation of niches is called resource partitioning.

Niche differentiation is often evident from morphological character displacement.

We can think of resource partitioning as "the ghost of competition past“- circumstantial evidence of earlier interspecific competition

resolved by the evolution of niche differentiation.

The Galápagos finches provide a good example of character displacement in beak sizes & in the seeds that they can eat most efficiently.

Allopatric populations {in different places} of Geospiza fuliginosa and G. fortishave beaks (and seeds in diet) of similar size, but (see Fig 39.5)on an island where both species occur {sympatric}a significant difference in beak depth(and seeds size in the diet) has evolved.

Evolution of Character Displacement in Darwin's FinchesPR Grant & BR Grant (14 July 2006) Science 313 (5784), 224. | Full Text » | PDF

It is apparent that predationinfluences the distribution and abundanceof prey species - most obviously by

killing some and scaring the rest.

Predators & parasites can actually increase biodiversity,by preventing competitive exclusion:

A keystone predator blocks competitive exclusionby preferentially killing the most abundant (dominant) competitor. (R. Payne, Fig 53.15)

w/o starfisheating mussels,mussels displaceeverything else

Status and Ecological Effects of the World’s Largest CarnivoresWJ Ripple et al. Science 10 Jan 2014 343,1241484.Large-bodied animals play essential roles in ecosystem structuring and stability

through both indirect and direct trophic effects. Humans have disrupted this trophic structure

through both habitat destruction and active extirpation of large predators, resulting in large declines in numbers and vast contractions in their ranges.

Consistent with theory, empirical studies increasingly show that large carnivores have substantial effects on the structure and function of diverse ecosystems. Significant cascading trophic interactions,mediated by their prey or sympatric mesopredators, arise when some of these carnivores are extirpated from or repatriated to ecosystems.

Trophic Downgrading of Planet EarthJA Estes et al. Science 15 July 2011:Vol. 333, pp. 301-306Ecological theory has long predicted that major shifts in ecosystems

can follow changes in the abundance and distribution of apex consumers. Although such losses are widely viewed as an ethical and aesthetic problem,

recent research reveals extensive cascading effects of their disappearance in marine, terrestrial, and freshwater ecosystems worldwide.

These findings emphasize the urgent need for interdisciplinary research to forecast the effects of trophic downgrading on process, function, and resilience in global ecosystems.

Status and Ecological Effects of the World’s Largest CarnivoresWJ Ripple et al. Science 10 Jan 2014 343,1241484.

“My enemy’s enemyis my friend”(-) x (-) = +

Trophic Downgrading of Planet Earth JA Estes et al.

(A) Shallow seafloor community at Amchitka Island after and before the collapse of sea otter populations. Sea otters enhance kelp abundance (right) by limiting herbivorous sea urchins.

(B) The rocky intertidal zone of central California after (left) and before seastar exclusion. Pisaster increases species diversity by preventing competitive dominance of mussels.

(C) Long Lake (MI) with largemouth bass experimentally removed (left) and present (right). Bass indirectly reduce phytoplankton

(thereby increasing water clarity): big bass ea t small fish that eat zooplankton that eat phytoplankton: - x - x - = - net effect

(D) Fished (left) and unfished (right) coral reefs. Fishing lowers the competitive advantage of reef-building corals by removing large predators of small coral eating fish.

(E) Pools in a prairie margin stream lacking (left) and with (right) bass. The bass extirpate herbivorous minnows, promoting the growth of benthic algae.

Population trends of grassland birds in North Americaare linked to the prevalence of an agricultural epizootic [disease] in EuropeJJ Nocera & HM Koslowsky PNAS March 22, 2011 vol. 108 no. 12 5122-5126We present a striking illustration of a [global ecological] cascade in which

bovine spongiform encephalopathy (BSE; “mad cow disease”) outbreaks in Europe exerted pressure on global beef markets, subsequently affecting North American hayfields and grassland bird populations.

We found that (i) Imports {of beef} from North America increased 1 y after BSE outbreaks {Europe}; (ii) probably because fewer cattle remained, [in N Am.]

the hay harvest in North America was reduced 2 y after the outbreak; (iii) the reduced hay harvest yielded a positive response

in grassland bird populations 3 y after the outbreak.http://www.the-scientist.com/?articles.view/articleNo/29578/title/What-kills-cows--saves-birds/flagPost/51008/

Indirect effects can be projected globally by global markets

(From left to right) the Eastern Meadowlark, Grasshopper Sparrow, and Sedge Wren are among the

birds most sensitive to changes in hay production.

More BSE in Europe,more meadowlarks in Kansas

3 years later

Framing ecosystem services in the telecoupled AnthropoceneJ Liu et al. Frontiers in Ecology and the Environment 14, February 2016 Pages 27–36http://onlinelibrary.wiley.com/doi/10.1002/16-0188.1/abstract

We are on a very tiny spaceship earth and the support systems are being stressed.

The biomass distribution on EarthYinon M. Bar-On, Rob Phillips, and Ron Milohttp://www.pnas.org/content/115/25/6506?etoc=

https://www.theguardian.com/environment/2018/may/21/human-race-just-001-of-all-life-but-has-destroyed-over-80-of-wild-mammals-studyHumans just 0.01% of all life but have destroyed 83% of wild mammals.

The biomass of

The biomass distribution on Earth Yinon M. Bar-On, Rob Phillips, and Ron Milohttp://www.pnas.org/content/115/25/6506?etoc=

Why is Biodiversity Important?The complex web of inter-dependent ecosystems which constitute life on Earth includes us. We are part of that web and are entirely dependent on clean air, fresh water and healthy food for our survival.

Some people argue that … we have a responsibility to act as stewards of the planet, protecting nature for its own sake and ensuring our consumption levels are sustainable. [it’s the right thing to do]

Others take a more utlitarian approach and argue that we should protect nature on the basis of the present and potential use of elements of biodiversity as biological resources, and focus on maintaining the biosphere in a state which supports human life. [ I call the “potential use” perspective “insurance” ]

Scientists have been working on the development of clear and transparent ways of assigning a monetary value to some of the ecosystem functions on which we depend, such as the activity of bees and other pollinators, …These are known as 'ecosystem services’

[this is pretty risky – what if the monetary value of polar bears is too low?]

https://www.npr.org/2018/11/23/668555773/climate-change-is-already-hurting-u-s-communities-federal-report-saysNEWS November 23, 2018Climate Change Is Already Hurting U.S. Communities, Federal Report Says

Climate change is already causing more frequent and severe weather across the U.S., and the country is poised to suffer massive damage to infrastructure, ecosystems, health and the economy if global warming is allowed to continue,according to the most comprehensive federal climate report to date.

The fourth National Climate Assessment is the culmination of years of research and analysis by hundreds of top climate scientists in the country.

The massive report details the many ways in which global climate change is already affecting American communities, from hurricanes to wildfires to floods to drought.

"Climate change is already affecting every part of the United States, almost every sector of the United States, be it agriculture or forestry or energy, tourism," says George Mason University professor Andrew Light, who is one of the report's editors.

"It's going to hurt cities, it's going to hurt people in the countryside, and, as the world continues to warm, things are going to get worse."

https://nca2018.globalchange.gov/chapter/front-matter-about/

The Global Change Research Act of 1990 mandates that the U.S. Global Change Research Program (USGCRP) deliver a report to Congress and the President no less than every four years that “1) integrates, evaluates, and interprets the findings of the Program…; 2) analyzes the effects of global change on the natural environment, agriculture, energy production and use, land and water resources, transportation, human health and welfare, human social systems, and biological diversity; and 3) analyzes current trends in global change, both human-induced and natural, and projects major trends for the subsequent 25 to 100 years.”1

https://nca2018.globalchange.gov

1. CommunitiesClimate change creates new risks and exacerbates existing vulnerabilities in communities across the United States, presenting growing challenges to human health and safety, quality of life, and the rate of economic growth.

2. EconomyWithout substantial and sustained global mitigation and regional adaptation efforts, climate change is expected to cause growing losses to American infrastructure and property and impede the rate of economic growth …

6. HealthImpacts from climate change on extreme weather and climate-related events, air quality, and the transmission of disease through insects and pests, food, and water increasingly threaten the health and well-being of the American people, particularly populations that are already vulnerable.

8. Ecosystems and Ecosystem ServicesEcosystems and the benefits they provide to society are being altered by climate change, and these impacts are projected to continue. Without substantial and sustained reductions in global greenhouse gas emissions, transformative impacts on some ecosystems will occur; some coral reef and sea ice ecosystems are already experiencing such transformational changes.

Climate Change Is Victim Of 'Tragedy Of The Commons'November 27, DAVID KESTENBAUMOne reason it is so hard to slash carbon emissions

is that climate change occurs globally. [the benefits of it are global]The countries that produce the most greenhouse gas

all need to take action to fix the problem. [the costs to reducing it are local]That raises a classic economic dilemma called the tragedy of the commons.[ the tragedy results when selfish individuals over-exploit the public good or common resource: if I show restraint or invest in the future, you might cheat: “free ride” on my investment ]

Can humankind escape the tragedy of the commons?Stephen BattersbyProc Natl Acad Sci U S A. 2017 114(1): 7–10.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5224396/ [fairness and trust are critical]“It is difficult to imagine the

world coordinating when the most important country refuses even to play the game.”

slide 3Ah, there's nothing more exciting than science. You get all the fun of ... sitting still, being quiet, writing down numbers, paying attention ... Science has it all. - Principal Skinner

The Simpsons

A VISION FOR IMPLEMENTING CHANGEIN UNDERGRADUATE BIOLOGY EDUCATION (2011)

• Introduce the scientific process to students early …• Define learning goals so that they focus on … core concepts …• Relate abstract concepts in biology to real-world examples … • Make biology content relevant by presenting problems in a real-life context.• Develop lifelong science-learning competencies. {a primary goal for this class!}• Introduce fewer concepts, but present them in greater depth …• Demonstrate both the passion scientists have for their discipline

and their delight in sharing their understanding of the world with students.• Engage students as active participants, not passive recipients …• Ensure that undergraduate biology courses are

active, outcome oriented, inquiry driven, and relevant …• Introduce research experiences as an integral component … for all students …• Give students ongoing, frequent, and multiple forms of feedback on their progress.• …

I hope we’ve done a good job of moving you along on your adventureand that this leg of the journey was interesting and useful.