Transcript lecture on Fremontodendron decumbens (Pine

Reproductive Biology of the
Endangered Shrub,
Fremontodendron californicum subsp. decumbens,
and its Conservation Implications
Robert Boyd
Department of Biological Sciences
Auburn University
• 3 taxa recognized
• Species, or
subspecies
Fremontodendron
californicum
– Note F.
decumbens,1 site in
El Dorado County,
CA
Fremontodendron californicum
subsp. decumbens
• Found only near
Pine Hill
• 2,000 shrubs (<1 mi
radius)
• Listed federally
endangered 1996
Pine Hill from SE
Closer view Pine Hill chaparral
F. californicum subsp. decumbens
• Small shrub
• 1-2 meters tall
F. californicum
subsp. decumbens
• Beautiful flowers
• Fruit covered with
stiff trichomes
• Seeds: orange
appendage
(elaiosome)
Study: Reproductive Biology
• Document reproductive
attrition
• Mark flower buds
• Determine fates
Marking flower buds
in spring
Bud
marked
with
wire at
its base
Reproductive Biology
• Answer: insects attack flower
buds, flowers, fruits
• 1.8% flower buds survive to
produce seeds
Reproductive Biology
• Seed fates
• Predation: marked seeds
(elaiosomes removed) in
caged and uncaged locations
under shrubs
• After 9 mo: extract & count
surviving seeds
• Difference between
locations: rodent predation
Basic Reproductive Biology
• Seed fates: Predation
• Answer: 90% seeds
eaten by rodents
Reproductive Biology
• Seedling fates
• Seeds dormant unless
heat-treated
• Plant heat-treated
seeds in caged and
uncaged plots
• Document fates in
each case
Reproductive Biology
• Seedling fates
• Answer:
– Rodents eat some
– Insects eat most
– Rest die from summer
drought
Placerville CA rainfall
Reproduction Model
Today’s story
• Pollination: insect visitors to flowers
• Dispersal: ants attracted to elaiosomes
• Focus on pollination and seed dispersal
– Important life cycle stages
– Involve mutualist animals
Today’s story
• Pollination: insect visitors to flowers
• Dispersal: ants attracted to elaiosomes
• Focus on pollination and seed dispersal
– Important life cycle stages
– Involve mutualist animals
• What roles mutualists in plant reproduction?
• Conservation implications?
Focus on pollination
• Are insect visitors
required to make
fruits?
Focus on pollination
• Approach: enclose
branches to prevent
insect visits
• Mark flowers already
open (one color wire)
• Mark large flower
buds (another color)
Focus on pollination
•
•
•
•
Are insect visitors required to make fruits?
39 flower buds, 0% fruits
22 flowers open when bagged, 32% fruits
Answer……..
Focus on pollination
•
•
•
•
Are insect visitors required to make fruits?
39 flower buds, 0% fruits
22 flowers open when bagged, 32% fruits
Answer: Yes, visits required.
Focus on pollination
• What insects visit flowers? Which are likely
pollinators?
Focus on pollination
• What insects visit flowers? Which are likely
pollinators?
• Approach: watch flowers, document visitors
• June: two years
• 1,746 insect visits.
Focus on pollination
Answer: Native solitary bees
Bee species
Percent visits
Tetralonia stretchii
89.4%
Callanthidium illustre 8.7%
Apis mellifera
1%
Other native bees
2%
Focus on pollination
• Dominant visitor:
Tetralonia stretchii
Stretching for nectar
Nectaries
Gathering pollen
Focus on pollination
• What insects visit flowers? Which likely
pollinators?
• Answer: Native solitary bees.
Focus on pollination
• How effective are bees?
• Approach: compare fruit set and seed set handpollinated flowers.
Focus on pollination
• Fruit set not significantly different:
– Hand-pollinated 80% Bee-pollinated 70%
Focus on pollination
• Fruit set not significantly different:
– Hand-pollinated 80% Bee-pollinated 70%
• Seed set different:
– Hand-pollinated: 4.9 seeds/flower
– Bee-pollinated: 2.6 seeds/flower
Focus on pollination
• Fruit set not significantly different:
– Hand-pollinated 80% Bee-pollinated 70%
• Seed set different:
– Hand-pollinated: 4.9 seeds/flower
– Bee-pollinated: 2.6 seeds/flower
• Answer: All flowers pollinated, pollen amount
not maximized (seed set 53% of possible).
Focus on pollination
• How bees find flowers?
• Approach: UV photos
Focus on pollination
• How bees find flowers?
• Approach: UV photos
All light
UV light
Focus on pollination
• Summary:
– Native solitary bees essential to seed
production
– Not maximizing seed set, but maximizing
fruit set.
Focus on seed dispersal
• The ant connection
– Harvester ant: Messor andrei
– Attracted to elaiosomes, carry seeds to nests
(in openings chaparral)
– Discard some seeds on “midden”
Focus on seed dispersal
• How do ants modify reproductive attrition?
• How does ant dispersal benefit plant?
Focus on seed dispersal
• Possibilities:
– 1) Do ants stimulate seed germination (scarify
seeds)?
Focus on seed dispersal
• Possibilities:
– 1) Do ants stimulate seed germination (scarify
seeds)?
– 2) Do ants protect seeds from rodent predation by
moving them from under shrubs to open areas?
Focus on seed dispersal
• Possibilities:
– 1) Do ants stimulate seed germination (scarify
seeds)?
– 2) Do ants protect seeds from rodent predation by
moving them from under shrubs to open areas?
– 3) Do seedlings on ant middens have better chance
survival?
Focus on seed dispersal
• Possibilities:
– 1) Do ants stimulate seed germination (scarify
seeds)?
– 2) Do ants protect seeds from rodent predation by
moving them from under shrubs to open areas?
– 3) Do seedlings on ant middens have better chance
survival?
– 4) Do benefits occur after fire stimulates seed
germination?
Focus on seed dispersal
• 1) Do ants stimulate seed germination (scarify
seeds)?
• Compare germination of seeds
– Fresh from fruits
– Given to ants and recovered from midden.
Focus on seed dispersal
• 1) Do ants stimulate seed germination (scarify
seeds)?
– No statistical difference
% germination
Untreated seeds
Heat-treated seeds
2.6%
54%
Ant-handled seeds 5.4%
66%
Fresh seeds
Focus on seed dispersal
• 2) Do ants protect seeds from rodent predation
by moving them from under shrubs to open
areas?
Focus on seed dispersal
• 2) Do ants protect seeds from rodent predation
by moving them from under shrubs to open
areas?
– Seed trays in pairs
– Canopy edge, 0.5 m, 1 m away in open
– Seeds with elaiosomes one tray, without in other
Focus on seed dispersal
elaiosome
no elaiosome
– Compare seed removal
– No effect distance
– More with elaiosomes taken
Focus on seed dispersal
• 2) Do ants protect seeds from rodent predation
by moving them from under shrubs to open
areas?
– No, seeds not more safe in open
– But removal elaiosome helps seeds avoid rodent
predation
– This benefit of ant handling, but not benefit of
elaiosome presence.
Focus on seed dispersal
• 3) Do seedlings on ant middens have better
chance survival?
– Plant heat-treated seeds on middens and under
shrubs
– Cage some to protect from rodents
Ant midden
Under shrub canopy
Focus on seed dispersal
• Results: Mean seedling longevity in days (SD)
Ant midden
Caged
Uncaged
Canopy
27 (23)
46 (30)
17 (20)
34 (27)
Caging helps, survival on middens is less!
Focus on seed dispersal
• 4) Do benefits occur after fire stimulates seed
germination?
• Approach: experimental burn!
Focus on seed dispersal
• 4) Do benefits occur after fire stimulates seed
germination?
• Preparation/planning!
Focus on seed dispersal
• 4) Do benefits occur after fire stimulates seed
germination?
Focus on seed dispersal
• 4) Do benefits occur after fire stimulates seed
germination?
Aerial view
Ground view
Focus on seed dispersal
• Seedlings counted & marked during winter
(rainy) season following fire
• Most under canopy/at canopy edge
Focus on seed dispersal
• Survival higher away from canopy
Focus on seed dispersal
• Why?
• 1) Rodent predation greater
under canopy
Focus on seed dispersal
• Why?
• 2) Dispersed more likely near opening
created by death of shrub
• Many chaparral shrubs re-sprout after fire,
including Fremontodendron
Resprouting
Fremontodendron
Focus on seed dispersal
• Measure distance each seedling to nearest:
– Re-sprouting shrub
– Dead shrub
• If nearer dead than live: close to opening
Near dead…Mostly dead
Focus on seed dispersal
• Measure distance each seedling to nearest:
– Re-sprouting shrub
– Dead shrub
• If nearer dead than live: close to opening
Near to dead: not same
as “mostly dead”…..
Focus on seed dispersal
Fremontodendron
seedlings
Dead chamise shrub
Focus on seed dispersal
• Summary dispersal benefits (after fire):
– 1) Less rodent predation
– 2) Greater chance being near opening in
chaparral community.
Conservation Implications
• Pine Hill Reserve small (97
hectares)
• Surrounding area being developed
Cleared
area west
of
Pine Hill
Conservation Implications
• Pollination
– Native bees required
– These bees generalists
Conservation Implications
• Dangers
– How big reserve needed to protect bees?
– Neighborhood activities may threaten bees
• Insecticides off Reserve could harm bees
• Plantings off Reserve could draw bees away
Solution:
monitor
pollination
success
Conservation Implications
• Seed dispersal
– Native ants required
– Benefits accrue only after fire
Conservation Implications
• Seed dispersal
– Native ants required
– Benefits accrue only after fire
• Dangers
– How big reserve needed to protect ants?
– How land use in neighborhood affect ants?
• Land clearing, insecticide use, etc.
Final lessons for endangered
species management
• Consider these questions, plan for periodic
fire (stimulate germination)
• 1) Mutualists important
Most rare plants don’t
have pollinators/dispersers
identified
Final lessons for endangered
species management
• 1) Mutualists important
• 2) Habitat protection best way to
maintain web of life
• 3) Managers must integrate biology
with human needs/habitat uses
Final lessons for endangered
species management