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Reproductive Biology of the Endangered Shrub,
Fremontodendron californicum subsp. decumbens,
and its Conservation Implications
Robert BoydDepartment of Biological Sciences
Auburn University
• 3 taxa recognized
• As species, or as subspecies of Fremontodendron californicum
• Note F. decumbens, only 1 site in Eldorado County, California
Fremontodendron californicum subsp.
decumbens• Found only near Pine Hill
• About 2,000 shrubs counted (<1mi radius)
• Listed as federally endangered in 1996
Pine Hill from SE
• Beautiful copper-colored flowers
• Fruit covered with stiff trichomes
• Seeds have orange appendage (elaiosome)
Basic Reproductive Biology• Document
reproductive attrition
• Mark flower buds• Determine fates
Marking flower budsin spring
A bud markedwithwire atits base
Basic Reproductive Biology• Answer: insects
attack flower buds, flowers, fruits
• Only 1.8% of flower buds survive to produce seeds
Basic Reproductive Biology• Seed fates
• Predation: marked seeds (elaiosomes removed) in caged and uncaged locations under shrubs
• After 9 months extract and count surviving seeds
• Difference between caged/uncaged locations: rodent predation
Basic Reproductive Biology
• Seedling fates• Most seeds dormant unless heat-treated
• Plant heat-treated seeds in caged and uncaged plots
• Document fates in each case
Basic Reproductive Biology
• Seedling fates• Answer: • Rodents eat some
• Insects eat most
• Rest die from drought during summer
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 of mutualists in reproduction of plant?
• What are conservation implications?
Focus on pollination• Approach: enclose branches in bags to prevent insect visits
• Mark flowers already open with one color wire
• Mark large flower buds with another color
Focus on pollination• Are insect visitors required to make fruits?
• Of 39 flower buds, 0% fruits• Of 22 flowers open when bagged, 32% fruits
Focus on pollination• Are insect visitors required to make fruits?
• Of 39 flower buds, 0% fruits• Of 22 flowers open when bagged, 32% fruits
• Answer: Yes, visits required.
Focus on pollination
• What insects visit flowers? Which are likely pollinators?
• Approach: watch flowers to document visitors
• During June of two years• Document 1,746 insect visits.
Focus on pollination
Tetralonia stretchii
89.4%
Callanthidium illustre
8.7%
Apis mellifera 1%
Other native bees
2%
Bee species Percent of visits
Answer: Native solitary bees
Focus on pollination• Dominant visitor: Tetralonia stretchii
Stretching for nectar
Gathering pollen
Nectaries
Focus on pollination
• What insects visit flowers? Which are likely pollinators?
• Answer: Native solitary bees.
Focus on pollination• How effective are bees?• Approach: compare fruit set and seed set of hand-pollinated flowers.
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• Summary:–Native solitary bees essential to seed production
–Currently not maximizing seed set, but maximizing fruit set.
Focus on seed dispersal
• The ant connection–Harvester ant: Messor andrei–Attracted to elaiosomes of seeds
Focus on seed dispersal
• The ant connection–Discard some intact seeds on midden (waste pile) around nest entrance
–Nest entrances located in openings in chaparral
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)?
– 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 between fresh and ant-handled seeds
2.6% 54%
5.4% 66%
Untreated seeds
Heat-treated seedsFresh seeds
Ant-handled seeds
% germination
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?– Use seed trays placed in pairs– Place at canopy edge, 0.5 m, 1 m away in open
Focus on seed dispersal
• 2) Do ants protect seeds from rodent predation by moving them from under shrubs to open areas?– Use seed trays placed in pairs– Place at canopy edge, 0.5 m, 1 m away in open
– Put seeds with elaiosomes in one tray, without in other of each pair
– Compare seed removal.
Focus on seed dispersal
–No effect of distance–More seeds with elaiosomes taken
elaiosomeno elaiosome
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 of 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)
27 (23) 46 (30)
17 (20) 34 (27)
Ant midden
Canopy
Caged
Uncaged
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?
• Takes lots of preparation/planning!
Focus on seed dispersal
• 4) Do benefits occur after fire stimulates seed germination?
Aerial view Ground view
Focus on seed dispersal
• Seedlings counted and marked during winter (rainy) season following fire
• Most under or at canopy edge
Focus on seed dispersal• Why?
• 2) Dispersed seedlings more likely to be near opening created by death of shrub
• Many chaparral shrubs re-sprout after fire, including Fremontodendron
ResproutingFremontodendron
Focus on seed dispersal• Measure distance from each
seedling to nearest:– Re-sprouting shrub– Dead shrub
• Those nearer to dead than live: considered to be close to opening in community
Focus on seed dispersal• Measure distance from each
seedling to nearest:– Re-sprouting shrub– Dead shrub
• Those nearer to dead than live: considered to be close to opening in community
Near to dead: not same as “mostly dead”…..
Focus on seed dispersal
• Summary of dispersal benefits (after fire):– 1) Less rodent predation– 2) Greater chance of being near opening in chaparral community.
Conservation Implications
• Pine Hill Reserve is small (97 hectares)
• Surrounding area being developed
Clearedarea west ofPine Hill
Conservation Implications
• Pollination– Native bees are required– These native bees are generalists
Conservation Implications• Dangers
– How big a reserve is needed to protect the bees?
– Neighborhood activities may threaten bees•Insecticide use off of Reserve could harm bees•Plantings could draw bees away from the Reserve
Solution:monitorpollinationsuccess
Conservation Implications
• Seed dispersal– Native ants are required– Benefits accrue only after fire
Conservation Implications
• Seed dispersal– Native ants are required– Benefits accrue only after fire
• Dangers– How big a reserve is needed to protect the ants?
– How might land use in neighborhood affect ant populations?•Land clearing, insecticide use, etc.
Conservation Implications
• Seed dispersal– Native ants are required– Benefits accrue only after fire
• Dangers– How big a reserve is needed to protect the ants?
– How might land use in neighborhood affect ant populations?•Land clearing, insecticide use, etc.
• Need to consider these questions, plan for periodic fire to stimulate germination.
Final lessons for endangered species
management• 1) Mutualist organisms important
Most rare plants don’t have pollinators/dispersersidentified
Final lessons for endangered species
management• 1) Mutualist organisms important
• 2) Habitat protection best way to maintain the web of life
Final lessons for endangered species
management• 1) Mutualist organisms important
• 2) Habitat protection best way to maintain the web of life
• 3) Managers must integrate biology with human needs/habitat uses