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Lecture 14

lecture 14 notes from prof.Barrett

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Spencer Barrett

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Lecture 14: What Darwin saw: A geographical perspective on biodiversity and adaptation Recall: Charles Darwin’s Voyage Ÿ In his 20s; a ship’s naturalist Ÿ Most times in South America Ÿ Observed fossils, geographical distribution of plants and animals, and flora and fauna of oceanic island Ÿ Live in Oak woodland in England, characterized by low species diversity H.M.S. Beagle sails to Brazil….. Tropical Forest in Brazil Ÿ Very high species diversity of plant and animal groups compared with temperate zone. Ÿ Many biotic interaction, especially coevolved mutualisms between plants and animals Ÿ Year-round warmth results in rapid growth of insect and microbial populations, Pest and disease pressures on plants more intense Ÿ Q:How do they mate? A:,temperateàwind, rain forestàanimals! Summary Ÿ Tropical forests have high species diversity and individuals of the same species are widely separated-unlikely temperate forest Ÿ Tropical forests are also largely evergreen (non-deciduous) unlike most temperate forests Ÿ Dense canopies and long-distances between trees make winds a poor agent of pollen dispersal; animals are more effective pollinators Ÿ Bee, butterfly, moths, bird and bats pollinate most tropical trees; most temperate tree wind pollinated Euglossine Bees as long-distance pollinators of tropical plants (1971) Ÿ Used mark-recapture techniques to demonstrate that bees travel up to 23 km during a day Ÿ Today widely recognized that bees, moths and hummingbirds travel long distances during “trapline” foraging Ÿ Formulated pest pressure hypothesis o Predicts that tropical tree seedlings are less likely to establish close to the maternal parent, a result confirmed through field experiments o Adults individuals may harbor populations of specialized herbivore and pathogens that could readily infest nearby seeding o Escape from predators, herbivore, and pathogens may be one reason why some introduced species become invasive outside their native distribution o Ant-plant mutualism in Acacia Ÿ Ants benefits from plants by: o Nesting sites o Extrafloral nectaries- sugar o Beltian bodies-protein Ÿ Plants benefits from Ants by: o Ants protect plants against herbivorous insects Megan Frederickson’s experiment on Devil’s garden in Peru Ÿ In this place, only one plant grow (Duroia Hirsuta) o This is because that ant defends their hosts against plant competitors using formic acid as an herbicide thus benefitting from more nest sites. Giant Amazon Water Lily- spot the difference in appearance (wild & Botanical Garden) Intense herbivory in tropical ecosystems results in considerable damage and consumption of plant biomass Epiphytes Ÿ Common in the tropicsàincreasing species diversity Ÿ Epiphytic life form has evolved independently in many unrelated families=convergent evolution Ÿ Epiphytes are not parasite, they do not feeding on host plants Living leaf mimicryàPreying mantid Death leaf mimicryàKatydid Pollinator signalingàchange color after pollinated Anti-herbivore strategyàsome plants are red, because insects cannot see thecolor red. What is the function of the red bracts? Colored bracts attract pollinators Darwin finds fossils of extinct mammals in Brazil Giant armadillo (犰狳) The beagle heads South to Patagonia and Darwin discovers strikingly different environment in which abiotic factors dominate and landscapes are geological young Abrupt tree line governed by abiotic factors Familiar and unfamiliar animal groups in Patagon
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