administration Quizzes

Quiz 3: done Quiz 4 (Chapters 11 and 8): December 15

If new syllabus not sent to be by the end of the day, status quo will apply

Thus far: Homework received from: Joelle, Antoine, Angie, Mireille. You all have until midnight tonight. Typed. With reflection pieces.

No documentary this Thursday; lecture on 9-11 and civil society

Make-Ups – 12.45 – 1.45 pm – Khoury 309 Thursday December 16 Thursday January 6 Thursday January 13 Thursday January 20

No Class: December 22

Do read excerpt from: “Eating Animals”

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Food, Inc.

Wikileaks and Food, Inc.

Wikileaks and Environment

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Chapter 8: Evolutionary Ecology

Evolutionary ecology: already discussed

“Nothing in ecology makes sense, except in the light of evolution”

Many areas in ecology where evolutionary adaptation by natural selection takes center stage

Evolutionary ecology Importance of defenses that have evolved to protect plants

and prey from their predators Patterns in life histories that correspond to habitats in which

they have evolved Optimal foraging: evolution of behavioral strategies that

maximize predator fitness and thus mold their dynamic interactions with their prey

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Evolutionary ecology: other aspects

Coevolution

Evolutionary differentiation within and between species

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Molecular ecology

Knowing how much differentiation there is within species, or between one species and another, is critical for an understanding of their dynamics, and for managing those dynamics Is the pop offspring locally born? Immigrants? Who is most closely related to whom? Relevance?

Use of molecular, genetic markers Yes, read box 8.1

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Albatross Largest wingspan 21 recognized species; 19

‘threatened’ and other 2 are ‘nearly threatened’

Why? - interaction with fishing

operations, particularly longlines. A typical longlining operation involves releasing a single line (that may be up to 100km long) off the stern of the boat with as many as 3,000 baited hooks along its length. They are common ship followers and strike at the baited hooks as they are being set, subsequently drowning when the line sinks below the water.

- pollution

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The great garbage patch, kills over 10,000 albatross each year. 

Unfortunately, many albatross mistake the garbage for food and die quite painful deaths from the consumption of plastics and other toxins.

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Differentiation within species

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Black-browed albatross T. impavida (Campell Island) T. melanophris (sub-Antarctic)

Gray-headed albatross Breeds on a number of the

same islands as T. melanophris

?: how connected or separate are these populations? Should conservation efforts be directed at what are currently thought to be whole species or at particular breeding populations?

Albatross and molecular marking

Study confirmed that T. impavida was a separate species

Study demonstrated breeding between T. impavida and T. melanophris

Wider ranging gray-headed albatrosses – from all five of their sites – represent a single breeding population

Conservation perspective: Falkland Islands also support a breeding population of T. melanophris

Thus?

Yes: Box 8.2

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Red wolf

Canis rufus – decreasing distribution (1700 to 1970)

1970: 14 individuals were rescued, bred in captivity to be reintroduced

C. rufus exists with two related species, C. lupus (gray wolf) and coyote C. latrans

Is the red wolf a hybrid from interbreeding gray wolf and coyote?

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Red wolf and conservation

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“Should the conservation status of the red wolf, and the amount of money spent on its conservation, be downgraded if it is acknowledged that it is ‘only’ a hybrid and not a full species?

A phylogenetic tree. Most related are placed closest together. Lengths of horizontal lines represent degree of difference

Arrow – single genotype shared by 8 captive red wolves sampled

Coevolutionary arms races

Coevolution: remember?

Coevolution: reciprocal evolution in two or more interacting species of adaptations selected by their interaction

Evolution of both consumer and prey depend crucially on evolution of the other

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Insect-plant arms races

Remember: attacks by herbivores select for plant-defensive chemicals? Remember: qualitative chemicals and quantitative chemicals?

Qualitative – can kill in small doses; induced by herbivore attacks

Quantitative - rely on accumulation of ill effects; digestion-reducing; produced all the time

Toxic chemicals – by virtue of their specificity – are likely to be the foundation of an arms race

Plants relying on toxins are more prone to becoming involved in arms races with their herbivores (ex: beetle and legume) than those relying on more ‘quantitative chemicals’

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Questions …

Do specialist herbivores generally, locked in their coevolutionary arms races, perform better when faced with their plants’ toxic chemicals than generalists,

Do generalists, having invested in overcoming a wide range of chemicals, perform better than specialists when faced with chemicals that have not provoked coevolutionary responses?

Answered…by analyzing wide range of data set for insect herbivores fed on artificial diets with added chemicals More specialized insects suffered lower mortality on chemicals

that have provoked a coevolutionary response from specialist herbivores

More generalist insects suffered lower mortality on chemicals that not provoked a coevolutionary response from specialist herbivores

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Coevolution of parasites and their hosts

Common to find high degree of genetic variation in virulence [highly infective] of parasites and/or in resistance or immunity of hosts

Every few years: a new strain of influenza virus

No strain more devastating than worldwide epidemic [pandemic] of Spanish flu (a subtype of avian strain H1N1) [killed 20 million, 1918/1919]

May seem straightforward that: Parasites select for evolution of more resistant hosts in turn select for more infective parasites

More complicated…

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Coevolution of parasites and their hosts

Yes: examples where host and parasite drive one another’s evolution

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The rabbit/myxoma story

19Interacting populations evolve in response to each other

Evolution of Resistance in Rabbits

Decline in lethality of the myxoma virus in Australia resulted from evolutionary responses in both the rabbit and the virus populations: genetic factors conferring resistance to the disease

existed in the rabbit population prior to introduction of the myxoma virus: the myxoma epidemic exerted strong selective pressure

for resistance eventually most of the surviving rabbit population

consisted of resistant animals less virulent strains of virus became more prevalent

following initial introduction of the virus to Australia: virus strains that didn’t kill their hosts were more readily

dispersed to new hosts (mosquitoes bite only living rabbits)

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The Rabbit-Myxoma System Today

Left alone, the rabbit-myxoma system in Australia would probably evolve to an equilibrial state of benign, endemic disease, as in South America [pest management specialists continue to introduce new, virulent strains to control the rabbit population]

Wait. Parasites favored by natural selection are those with the greatest fitness (greatest reproductive rate) – sometimes achieved through decline in virulence, sometimes not

Further declines in myxoma virus not favored

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Myxoma virus

Blood-borne

Transmitted from host-host by blood-feeding insect vectors 1st 20 years after introduction to Australia, main vectors were

mosquitoes, which feed only on live hosts Grade I and Grade II viruses kill host quickly As densities decline, effective transmission becomes impossible Selection against Grade I and Grade II in favor of less virulent

grades

Rabbit flea – favored more virulent strains

Selection NOT for decreased virulence – but for increased transmissibility which is maximized by intermediate grades of virulence

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The rabbit/myxoma story: … is an example of a predator (the virus) and prey (the rabbits).

And an example of coevolution of parasite and host

Note: Contagious diseases spread through the atmosphere or water are less likely to evolve hypovirulence, as they are not dependent on their hosts for dispersal.

Host-parasitic coevolution: agricultural plants

Increased resistance in the host – increased infectivity in the parasite

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Mutualistic interactions

No species lives in isolation

Some associations are particularly close: habitat they occupy IS an individual of another species Parasites Nitrogen-fixing bacteria

Symbiosis -> ‘living together’ – a symbiont occupies a habitat provided by a host; parasites usually excluded; suggestion of mutualistic interaction

Mutualism: organisms of different species interact to their mutual benefit; do not have to be symbionts Not necessarily conflict-free relationships – but ‘net’ beneficiaries

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Mutualistic protectors

Cleaner fish 45 species: feed on

ectoparasites, bacteria, and necrotic tissue

Grouper fish Bullethead parrrotfish goes to

the cleaning station off the coast of Palestine

Green sea turtle

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Mutualistic protectors: plants and ants

Ants: the protector

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Ants protecting Acacia from elephants? - # > size

Mutualism: dispersal of seeds and pollen

- feeding on fruits and dispersing the seeds – and not just disperse the seeds

- pollination: bees, hummingbirds, bats, small rodents and marsupials

- insect pollinators: the best Some specialist,

protected nectars (R. bulbusos). Why?

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Mutualism: gut inhabitants, not just in cows

Live entirely ‘within’ its partner

Crucial role of microbes in digestion of cellulose by vertebrate herbivores

Gastrointestinal tracts of all vertebrates are populated by a mutualistic microbiota

Major contributors: bacteria

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mycorrhiza Intimate mutualisms between fungi and root

tissue. [Cruciferae are exception]

(1) arbuscular –found in 2/3 – most non-woody and tropical trees

(2) ectomycorrhizal – symbioses with many trees and shrubs – boreal and temperate mostly

(3) ericoid mycorrhiza- dominant plant species of heathland

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Ectomycorrhizas (ECM) Infected roots: [ ] in litter layer of soil

Fungi form a sheath of varying thickness around the roots

Hyphae radiate into litter layer – getting nutrients and water

Fungal mycelium penetrates between cells of root cortex and establishes interface for the exchange of products of photosynthesis between host and fungal partner

ECM growth: directly related to rate of flow of hexose sugars from the plant; when nitrate availability is high – EM degrades

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Arbuscular mycorrhizal

Penetrate within the roots of the host; do not form sheath

Initially: fungus grows between host cells but then enters them and forms a finely branched intercellular ‘arbuscule’

Benefits: nitrogen and phosphorus uptake, pathogen and herbivore protection, and resistance to toxic metals

Details/extent – depend on the species

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Mutualism: fixation of atmospheric nitrogen

Mutualisms of rhizobia and leguminous plants – several steps

Be familiar with the costs and benefits

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End of chapter 8

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