Robert Boyd Department of Biological Sciences Auburn University

Reproductive Biology of the Endangered Shrub,

Fremontodendron californicum subsp. decumbens,and its Conservation Implications

Robert BoydDepartment 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 budsin spring

Bud markedwithwire atits 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

Tetralonia stretchii 89.4%

Callanthidium illustre 8.7%

Apis mellifera 1%

Other native bees 2%

Bee species Percent visitsAnswer: Native solitary bees

Focus on pollination• Dominant visitor:

Tetralonia stretchiiStretching for nectar

Gathering pollen

Nectaries

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 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

– 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

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?– 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

– Compare seed removal– No effect distance– More 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 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?• 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

ResproutingFremontodendron

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

Dead chamise shrub

Fremontodendron seedlings

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

Clearedarea west ofPine 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:monitorpollinationsuccess

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/dispersersidentified

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