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

Closer view of Pine Hill chaparral

F. californicum subsp. decumbens

• Small shrub• 1-2 meters tall

F. californicum subsp. decumbens

• 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• Seed fates:

Predation• Answer: 90% seeds eaten by rodents

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

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 of mutualists in reproduction of plant?

• What are conservation implications?

Focus on pollination• Are insect visitors required to make fruits?

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?

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%

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

UV lightAll light

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–Carry seeds to nest–Remove elaiosome

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)?

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?

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

• Survival higher for those dispersed away from canopy

Focus on seed dispersal

• Why?• 1) Rodent predation greater under shrub canopy

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

Dead chamise shrub

Fremontodendron seedlings

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

Final lessons for endangered species

management