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Lecture 14

BIO120H1 Lecture Notes - Lecture 14: Nectar, Giant Armadillo, Temperate Climate


Department
Biology
Course Code
BIO120H1
Professor
Spencer Barrett
Lecture
14

Page:
of 6
Lecture 14: What Darwin saw: A geographical perspective on biodiversity and adaptation
Recall: Charles Darwins Voyage
Ÿ In his 20s; a ships 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 QHow 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 Fredericksons experiment on Devils 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 the color 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 Patagonia
· Bumblebees à bigger, black. To keep warm
· Black-necked swan
· Guanaco àlooks like camel
· Darwins Rhea àDarwin ate one = =
Adaptation to animal razing in Patagonia
Spiny cushion plants are
avoided by grazing animals
Fruits with adhesive hooks
dispersed on animal fur.
H.M.S sailed to Galapagos Islands.
Galapagos Islands
· 15 main islands of volcanic origin; oldest 5-10 million years old; youngest more recent
· Flora and fauna colonized by species capable of long-distance dispersal from South
American mainland
· Distinct races and species on difference islands provide evidence of early stages of
speciation
· Darwin spent only 5 weeks on the islands but his observation formed the foundation for