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Reproductive Biology of the Endangered Shrub, Fremontodendron californicum subsp. decumbens, and its Conservation Implications Robert Boyd Department of.

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Presentation on theme: "Reproductive Biology of the Endangered Shrub, Fremontodendron californicum subsp. decumbens, and its Conservation Implications Robert Boyd Department of."— Presentation transcript:

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 Tetralonia stretchii89.4% Callanthidium illustre8.7% Apis mellifera1% Other native bees2% Bee species Percent visits Answer: Native solitary bees

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

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 UV lightAll 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 2.6%54% 5.4%66% Untreated seedsHeat-treated seeds Fresh seeds Ant-handled seeds % germination

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 middenUnder shrub canopy

45 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!

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 viewGround view

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

51 Focus on seed dispersal Survival higher away from canopy

52 Focus on seed dispersal Why? 1) Rodent predation greater under canopy

53 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 Resprouting Fremontodendron

54 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

55 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”…..

56 Focus on seed dispersal Dead chamise shrub Fremontodendron seedlings

57 Focus on seed dispersal Summary dispersal benefits (after fire): –1) Less rodent predation –2) Greater chance being near opening in chaparral community.

58 Conservation Implications Pine Hill Reserve small (97 hectares) Surrounding area being developed Cleared area west of Pine Hill

59 Conservation Implications Pollination –Native bees required –These bees generalists

60 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: monitor pollination success

61 Conservation Implications Seed dispersal –Native ants required –Benefits accrue only after fire

62 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.

63 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/dispersers identified

64 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

65 Final lessons for endangered species management


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