Chap. 8 Evolutionary EcologyChap. 8 Evolutionary Ecology鄭先祐 (Ayo)

國立臺南大學 環境與生態學院生物科技學系 生態學 (2008)

Essentials of Ecology 3rd. Ed.

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Evolutionary EcologyEvolutionary Ecology

• 8.1 introduction

• 8.2 molecular ecology: differentiation within and between species

• 8.3 coevolutionary arms races

• 8.4 mutualistic interactions

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8.2 molecular ecology8.2 molecular ecology

• 8.2.1 differentiation within species

• 8.2.2 differentiation between species

Fig. 8.1 distribution of two distinct ‘clades’ of the Asian elephant, Elephas maximus, revealed only by an analysis of molecular markers.

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Box 8.1 Molecular makersBox 8.1 Molecular makers

• Choosing a molecular marker

• Polymerase chain reaction (PCR)

• Nuclear and mitochondrial DNA

• Microsatellites

• Sequencing

• Restriction fragment length polymorphism (RFLP)

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8.2.1 differentiation within species8.2.1 differentiation within species

• Albatrosses ( 信天翁 ), wide ranging sea birds with the largest winspans of any birds alive today, but of the 21 species normally recognized, 19 are regarded a ‘threatened’ with extinction and other two as ‘near threatened’.

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• Fig. 8.3 population differentiation in albatrosses. (a) distribution of sites in the sub-Antarctic from which samples were taken.

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• Fig. 8.3b. The relationships amongst 73 black-browed albatrosses in the base sequence at a focal, variable site in their mtDNA. While individuals from the same site shared exactly the same sequence.

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• Fig. 8.3c the relationships amongst 50 gray-headed albatrosses in the base sequence at a focal, variable site in their mtDNS.

The cross-hatches represent the number of base differences between the individuals they join.

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8.2.2 differentiation between species: the red wolf

8.2.2 differentiation between species: the red wolf

• Fig. 8.4a the geographic range of the red wolf, Canis rufus, in US around 1700, and within that the smaller bounded area shoing its range in southeastern Texas around 1970.

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• Fig. 8.4b a phylogenetic tree of coyote and red wolf mtDNA restriction-site genotypes (RFLPs).

• (c) a phylogenetic tree constructed on similar principles but based on sequences of the cytochrome 6 gene in the mtDNA.

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• Fig. 8.3d. The relationships between various coyote, gray wolf and red wolf populations at 10 nuclear DNA microsatellite loci, as demonstrated by an analysis that condenses the data from these 10 loci into to dimensions.

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8.3 coevolutionary arms races8.3 coevolutionary arms races

• 8.3.1 coevolution

• 8.3.2 insect-plant arms races (Fig. 8.5)

• 8.3.3 coevolution of parasites and their hosts

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8.3.2 insect-plant arms races8.3.2 insect-plant arms races• Specialists are more prone to arms races

Fig. 8.5 insect herbivores were split into three groups: 1, specialists; 2, oligophages; and 3, generalists.

(a) Those that are found in the normal hosts of the specialists and oligophages, and (b) those that are not.

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8.3.3 coevolution of parasites and their hosts

8.3.3 coevolution of parasites and their hosts

• Fig. 8.6 the mortality rate due to tuberculosis ( 肺結核 ) in three generations of Canadian Plains Native Americans after their forced settlement onto reservations.

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• Fig. 8.7 (a) the percentages in which various grades of myxoma virus have been found in wild population of rabbits in Australia (1951-1981)

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• Fig. 8.8• (a) over

evolutionary time (1 transfer = 8 bacterial generations) bacterial resistance to page increased in each of 12 bacterial replicates (different symbols).

• (b) similarly, phage infectivity increased.

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8.4 mutualistic interactions8.4 mutualistic interactions

• No species lives in isolation, but often the association with other species is especially close:– Symbiosis– Mutualism

• 8.4.1 mutualistic protectors• 8.4.2 the culture of crops or livestock• 8.4.3 the dispersal of seeds and pollen• 8.4.4 mutualistic gut inhabitants• 8.4.5 Mycorrhizas• 8.4.6 fixation of atmospheric nitrogen in

mutualistic plants

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8.4.1 mutualistic protectors8.4.1 mutualistic protectors

• Cleaner fish, of which at least 45 species have been recognized, feed on ecto-parasites, bacteria and necrotic tissue from the body surface of client fish.

Fig. 8.9 cleaner fish really do clean their clients.

(a) In a long-term experiment, clients without cleaners had more parasite after 12 days.

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• Fig. 8.9• (b) in a short-

term experiment, clients without cleaners did not have significantly more parasites at dawn after 12 hours.

• (c) however, the difference was significant after a further 12 hours of daylight.

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Ant-plant mutualismsAnt-plant mutualisms

• Fig. 8.10 Acacia and ants• (a) protein-rich Beltian bodies at the

tips of the leaflets• (b) hollow thorns used by the ants

as nesting sites.

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• Fig. 8.11 (a) intensity of leaf herbivory on plants naturally occupied by the ants (black dots) and on plants from which the ants had been experimentally removed (gray dots.)

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• Fig. 8.11• (b) the longevity

of leaves on plants occupied by the ant and from which ants (control) were experimentally removed or from which ants were naturally absent.

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8.4.2 the culture of crops or livestock8.4.2 the culture of crops or livestock

• Aphids farmed by ants

Fig. 8.12, (a) Ant-excluded colonies of the aphid were more likely to become extinct than those attended by ants.

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8.4.3 the dispersal of seeds and pollen8.4.3 the dispersal of seeds and pollen

• Fig. 8.13 Pollinators

• (a) honey bee

(b) Cape sugarbird

Generalists to ultra-specialists

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8.4.4 mutualistic gut inhabitants8.4.4 mutualistic gut inhabitants

• The crucial role of microbes in the digestion of cellulose by vertebrate herbivores has long been appreciated, but it now appears that the gastrointestinal tracts of all vertebrates are populated by a mutualistic microbiota.

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8.4.5 Mycorrhizas8.4.5 Mycorrhizas

• Ectomycorrhizas (fungi)

• Arbuscular mycorrhizas, penetrate within the roots of the host.– Fig. 8.14 (a) Curves fitted to rates of

phosphorus inflow and root colonization by arbuscular mycorrhizas fungi (solid line) in the bluebell, over a single growing season. Phosphorus uptake appears to be storngly linked to root colonization by the fungi.

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• Fig. 8.14 (a)

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8.4.6 fixation of atmospheric nitrogen in mutualistic plants

8.4.6 fixation of atmospheric nitrogen in mutualistic plants

• Mutualisms of rhizobia and leguminous plants.( 豆科植物 )

• Cost and benefits of rhizobial mutualisms• The shifting balance between nitrogen-

fixers and non-fixers– Fig. 8.15 the growth of soybeans (Glycine

soja, G, O) and a grass (Paspalum, P, ●) grown alone and in mixtures with and without nitrogen fertilizer (N) and with and without inoculation with nitrogen-fixing Rhizoblum (R).

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• N: 氮肥• R: 固氮菌• ○ ： soybeans• ● ：草， Paspalum sp.

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Questions Questions

• Account for the decline in virulence of the myxomatosis virus in European rabbits after its initial introductions in Australia and Europe.

• Discuss the following propositions:– Most herbivores are not really herbivores but

consumers of the byproducts of the mutualists living in their gut and

– Most gut parasites are not really parasites but competitors with their hosts for food that the host has captured.

Japalura@hotmail.com

Ayo 台南站 http://mail.nutn.edu.tw/~hycheng/ 國立臺南大學 環境與生態學院 Ayo 院長的個人網站

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