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Relationship between age, size and reproduction in populations of American ginseng across a range of harvest pressures
Emily H. Mooney, Ph.D.Massachusetts College of Liberal Arts
2/24/2009
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Overview
Evolutionary implications of harvest Case studies from animal and plant speciesEvidence for selective harvest in American ginsengStudy details
MethodsResultsConclusions
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Wild harvested species
All images from www.wikimedia.org
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Harvest often targets specific phenotypes
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Harvest can lead to evolutionary change in natural populations
Assuming portion of variation is genetically determined
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CASE STUDY: declines in horn and body size linked to trophy hunting in bighorn rams, Ovis
canadensis
Coltman
et al. 2003. Nature. 426: 655-658.
wikimedia.org
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CASE STUDY: Size selective harvest in fisheries can result in life history change
Fish Species Selection responseLake whitefish, Coregonus
clupeaformis Smaller body size; slower growth
Atlantic salmon, Salmo
salar Smaller size at maturity
Pink salmon, Oncorhynchus
gorbuscha Smaller size at maturity
Chinook salmon, O. tshawytscha Smaller size at maturity
European grayling, Thymallus
thymallus Earlier age at maturity
Atlantic cod, Gadus
morhua Earlier age at maturity
Orange roughy
, Hoplostethus
atlanticus Increased fecundity
European plaice, Pleuronectes
platessa Earlier age at maturity
Hutchings, JA, Fraser, DJ. 2008. Mol Ecol. 17: 294–313
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CASE STUDY: Decline in height of the harvested snow lotus, Saussurea
laniceps
Law, W, Salick, J. 2005. PNAS. 102(29): 10218-10220.
S. laniceps S. medusa
Harvested Not Harvested
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Similar declines observed in ginseng from herbarium specimens
McGraw, JB. 2001. Biol
Cons. 98(1): 25-32.
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Harvest of ginseng is size selective
1.
Harvest often restricted to plants with 3 or more leaves
2.
Harvesters are likely motivated to leave behind juvenile plants
a)
Larger plants yield more valuable roots
b)
Traditional conservation ethics
3.
Larger plants are more apparent
Mooney, EH, McGraw, JB. 2007. Cons Gen. 8: 57-67.Price, ET. 1960. Geog Rev. 50: 1-20.Van der
Voort
, ME, McGraw, JB. 2006. Biol
Cons. 130: 505-516.
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Is variation in size genetically determined?
Germplasm bank planted by Bob BeyfussPlants collected from wild populations in eight statesDifferences in leaf area and sympodium height persisted
Common Environment
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Do life-history traits vary among populations with different harvest pressures?
Research Question
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How to assess harvest pressure?
Monitor population
Ask harvesters
Legal status of location
Stage-structure impacts
…potential for bias
…harvest infrequent
…poaching common
Bailey, B. 1999. Ph.D. Dissertation. WVU, Morgantown, WVVan der
Voort
, ME, McGraw, JB. 2006. Biol
Cons. 130: 505-516.van Manen, FT et al. 2005. Nat Areas J,
25: 339-350.
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Experimental harvest
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Year
Prop
ortio
n of
see
dlin
gs a
nd ju
veni
les
Pre-Harvest
Van der
Voort, ME, et al. 2003. Am. Midl. Nat.
149: 282-292
HARVEST INDEX
NJuvenilesSeedlings +
=
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Study populations
IN
WV
PA
NY
VA
MD
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Data collection
2004-2006Size
Sympodium (stem) heightLeaf area
Reproductive dataFlowering (Y/N)Seed production (Y/N)Number of seeds
AgeFrequency of deer browse
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Aging plants using stem scars
Camera lucida
drawings from www.fws.gov
Root collar
Aerial stem
Aerial stem
scars1 cm
Stem bud
Aerial stem
Adventitious root
1 cm
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Data analysis
Regression with model effects:
AgeHarvest IndexAge X Harvest Index
Correlation between deer browse and Harvest IndexStatistical software: SAS JMP v. 6.0
Sokal, RA, Rohlf, FJ. 1995. Biometry. W.H. Freeman and Company, New York.
Age
Trai
t
HI 0.1
HI 0.2
HI 0.3
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Results
Population Location N Harvest IndexVC Vermillion Co, IN 173 0.4122EP Lancaster Co, PA 99 0.4173EB Preston Co, WV 46 0.5057HP Albany Co, NY 280 0.5286CC Garrett Co, MD 154 0.6538LK Franklin Co, PA 349 0.6879GB Greenbrier Co, WV 123 0.7213TP Albany Co, NY 62 0.7235TR Parke Co, IN 133 0.7802PO Bedford Co, VA 300 0.7829AD Mercer Co, WV 75 0.8486RD Pulaski Co, VA 129 0.9583
Table 1: Study populations, their locations by county, mean population sizes over 2004-2006, and harvest indices.
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Results
Harvest Index0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Prop
ortio
n of
bro
wse
d pl
ants
0.00
0.05
0.10
0.15
0.20
VCEB
EP HPCC
LK
GB
TP
TRPORD AD
r
= 0.2348, p = 0.4871
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Results
0
10
20
30
40
50
60
0.4 0.5 0.6 0.7 0.8 0.9 1
Harves t Index
Age
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Results
Age
0 5 10 15 20
Pred
icte
d le
af a
rea
(cm
2 )
50
100
150
200
250
300
350
0.4 0.5 0.6 0.7 0.8 0.9
Harvest Index
N Model Term F
ratio p-value
650Age 908.905 <0.0001Harvest Index 6.756 0.010Age X Harvest Index 10.739 0.001
Table 2: Regression results for 2006
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Results
Age0 5 10 15 20
Pred
icte
d sy
mpo
dium
hei
ght (
cm)
6
8
10
12
14
16
18
20
22
0.4 0.50.60.70.80.9
Harvest Index
N Model Term F
ratio p-value
653Age 300.699 <0.0001Harvest Index 0.262 0.609Age X Harvest Index 12.046 0.001
Table 3: Regression results for 2006
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Results
Year Reproductive? Produced Seeds? Number of seeds
2004 χ2= 11.985, p=0.001 χ2= 2.510, p=0.113 F=3.293, p=0.074
2005 χ2= 44.953, p<0.0001 χ2= 13.630, p=0.0002 F=2.383, p=0.125
2006 χ2= 50.293, p <0.0001 χ2= 4.390, p=0.036 F=1.780, p=0.185
Table 4: Regression results describing the relationship between age and reproductive traits for plants in the 12 study populations. .
Likelihood of inflorescence production consistently increased with age
Age did not consistently predict seed production
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Results
Table 5: Regression results describing the relationship between harvest index and reproductive traits for plants in the 12 study populations. .
Year Reproductive? Produced Seeds? Number of seeds
2004 χ2= 3.259, p=0.071 χ2= 4.740, p=0.029 F=2.714, p=0.104
2005 χ2= 2.582, p=0.108 χ2= 0.580, p=0.446 F=23.041, p<0.0001
2006 χ2= 0.078, p=0.780 χ2= 22.630, p<0.0001 F=23.594, p<0.0001
Harvest index reduced likelihood of seed production in several study years
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Conclusions
Populations with higher harvest indices had plants with smaller leaf areas and sympodium heights
Appears to be the product of slower growthConsistent with the effects of size selective harvest
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Conclusions
Seed set and number of seeds was reduced in plants from populations with higher harvest indices
Not necessarily the product of size selective harvestAllee effectSimilar density-dependent reductions in fecundity observed in fisheries
Hackney, EE, McGraw, JB. 2001. Cons Biol. 15: 129-136Law, R. 2000. J Mar Sci.57: 659-668.
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Acknowledgments
Co-author: James B. McGrawDissertation committee: Brent Bailey, Jonathan Cumming, Steve DiFazio and Donna Ford-WerntzHelp in the field:
B. Beyfuss, P. Cox, L. DiIoia, P. Henderson, A. Hanna, S. Hovatter, M. Kaproth, C. Kimball, C. Kindlin, A. Martin, M. Olive, R. Parsons, S. Souther, K. Wixted and R. Wyman
FUNDING AGENCIES: