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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 • 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 coppercolored flowers • Fruit covered with stiff trichomes • Seeds have orange appendage (elaiosome) Basic Reproductive Biology • Document reproductive attrition • Mark flower buds • Determine fates Marking flower buds in spring A bud marked with wire at its 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 Answer: Native solitary bees Bee species Percent of 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 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 All light UV 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 anthandled seeds % 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? – 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 elaiosome no elaiosome – No effect of distance – More seeds 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 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) 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? • 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 Resprouting Fremontodendron 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 Fremontodendron seedlings Dead chamise shrub 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 Cleared area west of Pine 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: monitor pollination success 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/dispersers identified 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