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Robert Boyd Department of Biological Sciences Auburn University

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

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Robert Boyd Department of Biological Sciences Auburn University

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  1. Reproductive Biology of the Endangered Shrub,Fremontodendron californicum subsp. decumbens,and its Conservation Implications Robert Boyd Department of Biological Sciences Auburn University

  2. 3 taxa recognized • Species, or subspecies Fremontodendron californicum • Note F. decumbens,1 site in El Dorado County, CA

  3. Fremontodendron californicum subsp. decumbens • Found only near Pine Hill • 2,000 shrubs (<1 mi radius) • Listed federally endangered 1996 Pine Hill from SE

  4. Closer view Pine Hill chaparral F. californicum subsp. decumbens

  5. Small shrub • 1-2 meters tall F. californicum subsp. decumbens

  6. Beautiful flowers • Fruit covered with stiff trichomes • Seeds: orange appendage (elaiosome)

  7. Study: Reproductive Biology • Document reproductive attrition • Mark flower buds • Determine fates Marking flower buds in spring Bud marked with wire at its base

  8. Reproductive Biology • Answer: insects attack flower buds, flowers, fruits • 1.8% flower buds survive to produce seeds

  9. 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

  10. Basic Reproductive Biology • Seed fates: Predation • Answer: 90% seeds eaten by rodents

  11. Reproductive Biology • Seedling fates • Seeds dormant unless heat-treated • Plant heat-treated seeds in caged and uncaged plots • Document fates in each case

  12. Reproductive Biology • Seedling fates • Answer: • Rodents eat some • Insects eat most • Rest die from summer drought Placerville CA rainfall

  13. Reproduction Model

  14. 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

  15. 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?

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

  17. Focus on pollination • Approach: enclose branches to prevent insect visits • Mark flowers already open (one color wire) • Mark large flower buds (another color)

  18. Focus on pollination • Are insect visitors required to make fruits? • 39 flower buds, 0% fruits • 22 flowers open when bagged, 32% fruits • Answer……..

  19. 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.

  20. Focus on pollination • What insects visit flowers? Which are likely pollinators?

  21. Focus on pollination • What insects visit flowers? Which are likely pollinators? • Approach: watch flowers, document visitors • June: two years • 1,746 insect visits.

  22. Focus on pollination Answer: Native solitary bees Bee species Percent visits

  23. Focus on pollination Stretching for nectar • Dominant visitor: Tetralonia stretchii Nectaries Gathering pollen

  24. Focus on pollination • What insects visit flowers? Which likely pollinators? • Answer: Native solitary bees.

  25. Focus on pollination • How effective are bees? • Approach: compare fruit set and seed set hand-pollinated flowers.

  26. Focus on pollination • Fruit set not significantly different: • Hand-pollinated 80% Bee-pollinated 70%

  27. 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

  28. 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).

  29. Focus on pollination • How bees find flowers? • Approach: UV photos

  30. Focus on pollination • How bees find flowers? • Approach: UV photos All light UV light

  31. Focus on pollination • Summary: • Native solitary bees essential to seed production • Not maximizing seed set, but maximizing fruit set.

  32. 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”

  33. Focus on seed dispersal • How do ants modify reproductive attrition? • How does ant dispersal benefit plant?

  34. Focus on seed dispersal • Possibilities: • 1) Do ants stimulate seed germination (scarify seeds)?

  35. 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?

  36. 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?

  37. 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?

  38. 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.

  39. Focus on seed dispersal • 1) Do ants stimulate seed germination (scarify seeds)? • No statistical difference % germination Untreated seeds Heat-treated seeds Fresh seeds Ant-handled seeds

  40. Focus on seed dispersal • 2) Do ants protect seeds from rodent predation by moving them from under shrubs to open areas?

  41. 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

  42. Focus on seed dispersal • Compare seed removal • No effect distance • More with elaiosomes taken elaiosome no elaiosome

  43. 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.

  44. 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

  45. Focus on seed dispersal • Results: Mean seedling longevity in days (SD) Canopy Ant midden Caged Uncaged Caging helps, survival on middens is less!

  46. Focus on seed dispersal • 4) Do benefits occur after fire stimulates seed germination? • Approach: experimental burn!

  47. Focus on seed dispersal • 4) Do benefits occur after fire stimulates seed germination? • Preparation/planning!

  48. Focus on seed dispersal • 4) Do benefits occur after fire stimulates seed germination?

  49. Focus on seed dispersal • 4) Do benefits occur after fire stimulates seed germination? Aerial view Ground view

  50. Focus on seed dispersal • Seedlings counted & marked during winter (rainy) season following fire • Most under canopy/at canopy edge

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