administration Quizzes Quiz 3 done Quiz 4 Chapters

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 13 Thursday January 20 No Class: December 22 Do read excerpt from: “Eating Animals” 1

Food, Inc. Wikileaks and Environment 2

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 4

Evolutionary ecology: other aspects Coevolution Evolutionary differentiation within and between species 5

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 6

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 100 km 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 7

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. 8

Differentiation within species 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? 9

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 10

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? 11

Red wolf and conservation “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 12

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 13

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’ 14

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 15

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 H 1 N 1) [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… 16

Coevolution of parasites and their hosts Yes: examples where host and parasite drive one another’s evolution 17

The rabbit/myxoma story

Interacting populations evolve in response to each other 19

20 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)

21 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

Myxoma virus Blood-borne Transmitted from host-host by blood-feeding insect vectors 1 st 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 22

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 24

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 25

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 26

Mutualistic protectors: plants and ants Ants: the protector 27

Ants protecting Acacia from elephants? - # > size 28

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? 29

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 30

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 31

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 32

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 33

Mutualism: fixation of atmospheric nitrogen Mutualisms of rhizobia and leguminous plants – several steps Be familiar with the costs and benefits 34

End of chapter 8 35