BIOS 5970: Plant-Herbivore Interactions
Dr. Stephen Malcolm, Department of Biological Sciences
•  Week 8. Pollination
and fruit dispersal:
–  Lecture summary:
•  Mutualisms between
plants and animals:
–  Pollination
–  Seed and fruit
dispersal
–  Frugivory
Resplendent quetzal
dispersing wild avocado fruit
in Costa Rican cloud forest
Click here! for video
(Living Earth Foundation 1989.
The Rainforest)
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 1
2. Mutualisms:
•  Mutualisms exist when two or more species
enhance each other's fitnesses.
•  Symbiotic mutualisms involve species that
live in close physical contact.
•  But here we consider nonsymbiotic
mutualisms such as:
–  Pollination, seed dispersal and protection
•  see Table 6-1.
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 2
3. Pollination:
•  Angiosperm flower
evolved as an
elaborate device for:
–  (1) Capturing pollen
from other plants of
the same species.
–  (2) Distributing its own
pollen to other flowers
of the same species
(Fig. 6-1).
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 3
4. Flowers:
•  Petals and sepals are modified leaves with two key
functions:
–  (1) Attract animals with bright pigments, odors and
sometimes with nectar-producing tissues:
•  Apomorphic or derived characters.
–  (2) Protect the developing flower bud/ovary from
foraging insects:
•  Plesiomorphic or primitive characters.
•  Various pollinators attracted with a range of signals
(Table 6-2).
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 4
5. Pollinator rewards:
•  Sugar concentrations in nectar can vary from
15 to 88% by weight.
–  Ratios of different sugars also vary according to
the predominant pollinator group (Table 6-3):
•  Hummingbirds (neotropics) prefer a high ratio of
the disaccharide sucrose to the monosaccharides
glucose and fructose.
•  Sunbirds (old world) and some insects prefer lower
ratio of disaccharide:monosaccharide.
–  Amino acids highest in nectar of flowers that are
pollinated by species that do not eat pollen
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 5
6. Seed and Fruit dispersal:
•  Dispersal mutualisms older than pollination
mutualisms:
–  Cycad seeds dispersed by reptiles 200 million
years ago.
•  Today, up to 90% of trees and virtually all
the shrubs in tropical rainforests produce
fruits adapted to attract birds or mammals!!
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 6
7. Functions of angiosperm fruit:
•  (1) Nourishment for the diploid zygote from triploid
endosperm:
–  Carbohydrates, fats & protein (see Table 6-5).
•  (2) Protection:
–  From protective maternal diploid seed coat.
•  (3) Dispersal of plant embryos:
–  Dispersal structures:
•  Wings, nutritious aril (vertebrates) or elaiosome (ants).
–  Dispersal syndromes (Table 6-4) analogous to pollination
syndromes:
•  Predators may disperse seeds as they eat their seed-eating prey:
–  e.g. owls and finches in the Galapagos Islands
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
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8. Frugivory:
•  Fruit-eating birds and mammals that depend
on fleshy fruits for food are frugivores:
–  Often have color vision.
–  Visual and olfactory displays by plants are highly
conspicuous signals.
–  Herbivorous guts mostly destroy seeds inside fruit
–  But frugivores eat large amounts of fruit (low
protein) and often have short digestive tracts to
speed seed passage and ensure “gentle”
treatment while the consumer digests the pulp.
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 8
9. Plant manipulation of frugivore
dispersers:
•  Plants can produce laxatives that speed
seed passage rates and increase plant
reproductive success:
–  E.g. Murray, K.G., S. Russell, C.M. Picone, K.
Winnett-Murray, W. Sherwood, and M.L.
Kuhlmann. 1994. Fruit laxatives and seed
passage rates in frugivores: consequences for
plant reproductive success.
Ecology 75(4): 989-994.
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 9
Fruit pulp speeds passage of pioneer shrub fruits
through black-faced solitaires:
•  Cumulative
passage times of
natural fruits (●),
artificial fruits with
pulp extract (▲)
and artificial fruits
without pulp (￮).
•  Fig. 1 from Murray,
et al. 1994.
Ecology 75(4):
989-994.
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 10
Germination success of seeds decreases with
increased time in bird guts:
•  Fig. 2 from
Murray, et al.
1994. Ecology
75(4): 989-994.
–  Dashed line is
germination
success of
seeds removed
from fruits by
hand
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 11
Dispersal distance increases with
time spent in bird guts:
•  Fig. 3 from
Murray, et al.
1994. Ecology
75(4): 989-994.
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 12
Table 6-1:
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
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Table 6-3:
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 14
Table 6-4:
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 15
Table 6-5:
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 16
Bright red pigments attract hummingbirds:
Green hermit
hummingbird,
South
America
(Living Earth
Foundation
1989. The
Rainforest)
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 17
Orchid odors attract euglossine bees:
Euglossine bee in
Costa Rica leaving an
orchid with pollinia
attached to its back.
The orchid
manipulates the male
bee with pheromones
which the bee then
uses to attract females
(Living Earth Foundation
1989. The Rainforest)
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 18
Nectar and color
attract butterflies:
Dircenna dero butterfly in
Peru (Living Earth Foundation
1989. The Rainforest)
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 19
Tropical fruit diversity:
Diversity of
fruits with
toxic seeds
available to
foraging
macaws in
Peru
(National
Geographic
1994,
185(1): 130)
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 20
Macaws and hornbills eat fruit
pulp and disperse seeds:
Blue-and-yellow
macaw in Peru
Rhinoceros hornbill eating
strangler fig fruit in Borneo
(National Geographic 1997,
191(4): 41)
(National Geographic
1994, 185(1): 131)
BIOS 5970: Plant-Herbivore Interactions - Dr. S. Malcolm. Week 8: Pollination and fruit dispersal
Slide - 21