Transcript Rapid evolution or adaptive phenotypic plasticity as a mechanism of

Melissa Kerr
EPSCoR
Senior Honors Project
http://www.ancystrus.com.ar/articulos/daphnia.htm
•Majoring in zoology and
psychology
•Love Hawaii and the ocean!
•Graduating this semester
•Internship this summer at
Wildlife Safari in Oregon
Background: Rapid Evolution
 Evolution: slow process
over long time
 In actuality, evolution
occurs rapidly
 Difficult to see
 Happens too quickly, not
too slowly
 Right place, right time,
right traits
 Colonization leads to
rapid evolution
Background: Phenotypic Plasticity
 Change in trait w/o genetic change
 One genotype can produce multiple phenotypes
 Change induced by environment
 Not NEW traits, just fixation of EXISTING traits
 Moderate levels of PP makes species more adaptable
Background: Trophic Cascade
 Occurs when non-native
species comes into naïve
habitat
 Introduction of top trophic
level predator can influence
all the levels beneath it
 Much past research focused
on direct interactions of
invasive species
 But the interactions found
in a trophic cascade are
much more complex, and
many indirect interactions
occur
http://www.coralscience.org/main/articles/climate-a-ecology16/coral-reef-ecology
Yellowstone Lake
 Native cutthroat trout were top level
predator
 Eat zooplankton, microscopic animals
that live in the water
 Selectively feed on larger zooplankton
 1980s: Illegal introduction of lake
trout
 Piscivorous: fish-eating
 Lake trout eat the cutthroat trout
 Drastically reduced cutthroat trout
population size by 60%
http://www.nps.gov/yell/naturescien
ce/fisheries_issues.htm
http://www.northamericatrout.com/cutthr
oat.htm
Before
After
Tronstad et al., 2010
Yellowstone Lake
http://linnet.geog.ubc.ca/efauna
/photoGallery/ShowStandard.as
px?index=14104
 Change in life history traits?
 Dr. Amy Krist found body size at reproduction of
copepod, Leptodiaptomus ashlandi, was significantly
smaller before lake trout introduction
 Does this apply to other species of zooplankton as well?
Why the change?
 Three explanations:
Rapid Evolution
2. Adaptive Phenotypic Plasticity
3. Size-Selective Predation
1.
http://blog.auburn.edu/faa/?p=259
http://duffylab.biology.gatech.edu/InfectedDaphnia.html
Methods- Zooplankton of
Yellowstone Lake
Copepods
Hesperodiaptomus shoshone
Cladocerans
Daphnia schodleri
Diacyclops bicuspidatus
http://cyclot.sakura.ne.jp/gazoudata/kenmijinko/di
acyclops/diacyclops01b.html
Leptodiaptomus ashlandi
http://linnet.geog.ubc.ca/efauna/photoGalle
ry/ShowStandard.aspx?index=11597
Daphnia pulicaria
http://linnet.geog.ubc.ca/efauna/photoGallery/S
howStandard.aspx?index=14104
http://en.wikipedia.org/wiki/Daphnia
http://www.boldsystems.org/views/ta
xbrowser.php?taxid=4582
Methods
 Two sets of samples collected:
 1976-1981: pre-lake trout introduction


23 May to 19 October at four locations during daylight hours
Preserved in formalin
 2004: post-lake trout introduction


21 May to 19 October at same locations
Preserved in sugared formalin
Methods
 Subsampled approximately 20% of the sample
 Data collected:
 Body length


Length of carapace for cladocerans
Length of prosome and urosome for copepods
 Determined sex and brooding status
 Number of eggs (If present)
 Size of 5 random eggs (when present)
http://linnet.geog.ubc.ca/efauna/photo
Gallery/ShowStandard.aspx?index=1410
4
Results
 Only analyzed Daphnia pulicaria
 Most common cladoceran in Yellowstone Lake
 Only species with sufficient sample size
http://www.ancystrus.com.ar/articulos/daphnia.htm
Results
Year
Eggs/clutch
Body length (mm)
Mean egg length
Proportion
(mm)
brooding
1976-1981
3.26
1.92
0.309
57/1049 (5.4%)
2004
1.89
2.02
0.319
18/674 (2.7%)
Table 1. Life history traits of Daphnia pulicaria in Yellowstone Lake
collected prior to (1976-1981) and approximately 19 years after (2004) the
invasion of lake trout.
Results
Figure 1. The number of
eggs in a clutch of
Daphnia pulicaria in
relation to body size.
Clutch size was
significantly larger in the
pre-invasion samples of D.
pulicaria than in the postinvasion samples. Number
of eggs per clutch was not
predicted by female body
size.
=Before Lake Trout
=After Lake Trout
Results
Figure 2. The
probability of
reproducing increases
with larger body size in
Daphnia pulicaria. D.
pulicaria in the preinvasion samples were
much more likely to
reproduce than in the
post-invasion samples.
=Before Lake Trout
=After Lake Trout
Discussion
 Reduced predation = Delayed maturation
 More effort towards growth rather than reproduction,
thus smaller clutch sizes after introduction of lake trout
 Results of clutch size and proportion of brooding
individuals consistent with rapid evolution and
phenotypic plasticity
 Consistent with Dr. Krist’s previous findings with
copepods
 Not possible to distinguish between rapid evolution
and phenotypic plasticity
 Need further research
References










Koel, T.M., Bigelow, P., Doepke, P.D., Ertel, B.D., and D.L. Mahony. (2005) Nonnative lake trout result in Yellowstone
cutthroat trout decline and impacts to bears and anglers. Fisheries 30:10-19.
Krist, A., Tronstad, L., Thon, H., and Koel, T. (in revision) Life history shifts in a copepod (Leptodiaptomus ashlandi)
following the invasion of lake trout in Yellowstone Lake. Evolutionary Ecology.
Lass, S., & Spaak, P. (2003) Chemically induced anti-predator defences in plankton: a review. Hydrobiologia 491:221239.
Martinez, P.J., Bigelow, P., Deleray, M.A., Fredenberg, W.A., Hansen, B.S., Horner, N.J., Lehr, S.K., Schneidervin, R.W.,
Tolentino, S.A., and A.E. Viola. (2009) Western lake trout woes. Fisheries 34:424-442.
Munro, A. R., T. E. McMahon, and J. R. Ruzycki. (2005) Natural chemical markers identify source and date of
introduction of an exotic species: lake trout (Salvelinus namaycush) in Yellowstone Lake. Canadian Journal of Fisheries
and Aquatic Sciences 62:79- 87.
Price, T.D., Qvarnstrom, A., and Irwin, D.E. (2003) The role of phenotypic plasticity in driving genetic evolution. Proc.
R. Soc. Lond 270: 1433-1440.
Reznick, D. N., & Ghalambor, C. K. (2001) The population ecology of contemporary adaptations: what empirical
studies reveal about the conditions that promote adaptive evolution. Genetica 112-113: 183-198.
Simberloff, D. & Von Holle, B. (1999) Positive interactions of nonindigenous species: invasional meltdown? Biological
Invasions 1: 21-32.
Tronstad, L. M., Hall, R. O., Koel, T. M., and Gerow, K.G. (2010) Introduced lake trout produced a four-level trophic
cascade in Yellowstone Lake. Transactions of the American Fisheries Society 139: 1536-1550.
White, E. M., Wilson, J. C., and Clarke, A. R. (2006) Biotic indirect effects: a neglected concept in invasion biology.
Diversity and Distributions 12: 443-455.