Physiological and genetic mechanisms underlying population divergence across an altitudinal gradient...
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Transcript of Physiological and genetic mechanisms underlying population divergence across an altitudinal gradient...
Physiological and genetic mechanisms underlying population divergence across
an altitudinal gradient
Proposed Research
Jonathan Warner Atwell
Timothy James Grieves
Dawn Michelle O’Neal
Introduction
• Understanding mechanisms that underlie adaptive divergence is a central goal of evolutionary biology and ecology
• Investment in reproduction vs. survival is a ubiquitous life-history trade-off, and optimal strategies should vary with environment
• Few studies have robustly characterized physiological and genetic substrates of divergent life-history strategies
Local adaptation to seasonal environments
From Bronson 1990
•Breeding season length varies with latitude
• Life-history traits also vary with breeding season & latitude, including testosterone and immune function
•Similar differences are seen across an altitudinal gradient
• How has selection shaped the regulatory physiology of divergent mouse populations across an altitudinal gradient?
• Breeding phenology• Seasonal testosterone & immune function
• What are the genetic mechanisms underlying physiological variation?
• Divergent candidate genes
General Questions
Rocky Mountain Biological Laboratory
Alpine tundra
prairie grasslands
Subalpine forest
(Storz et al. 2004)
Field Capture methods
•Capture in baited sherman traps•Sample February-September
•Morphological measures•Assessment of reproductive condition (fondling)•Retro-orbital blood sample•Ear-tag and release
Breeding season
0
5
10
15
20
25
30
35
jan
jan fe
b
march
march
april
may
may
june ju
ly juy
aug
sept
spet oc
tnov
nov
dec
0
5
10
15
20
25
30
35
jan
jan
feb
march
march
april
may
may
june ju
ly juy
augsept
spet oc
tnovnov
dec
0
5
10
15
20
25
30
35
jan
jan
feb
march
march
april
may
may
june ju
ly juy
augsept
spet oc
tnov
nov
dec
Alpine tundra
Subalpine forest
Prairie grasslands
Measuring seasonal T and Innate Immune Function profiles…
-Capture free-living individuals each month before, during, & after breeding in both populations
-Collect sub-orbital blood samples
-Centrifuge blood, freeze plasma
-Conduct EIA assays to measure [ T ]
-Bacterial Killing Assays (Petri Dishes)
-Heamolytic Complement (EIA Plate)
= anti-testosteroneantibody
Y
Y Y
YY
Y
Y
Y
Y
Y
YY Y Y YYY Y YY YY
Y Y YY YY
= hormone in serum sample
= labeled hormoneof known amount
Y Y YY
ColorColor
Y Y
How do you measure hormones?
• Hypothesis: seasonal variation in T expression
Mountain MicePrairie Mice
T TTT
Immune Function
• Innate– Nonspecific antigen defense mechanisms – Bactericidal assay
• Measure of susceptibility
– Hemolytic complement• Measure of ability to respond
• Acquired/adaptive– Developed in response to specific antigens
• KLH– Antibody production
Alpine tundra
Subalpineforest
Prairie grassland
Hemolytic Complement Activity by Altitude
CH50
Alti
tud
e
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Prairie Grasslands
Subalpine Forest
Alpine Tundra
anti
-KL
H I
gG
(%
pla
te p
osi
tive
) Alpine Tundra
Prairie Grasslands
0
20
40
60
80
Acquired Immune Response (KLH)
Common garden study…
-Differences in behavior, hormones, immunity could be genetic or plastic
-Collect 20 males and females from each population from early in life (or pregnant females).
-Establish in common captive rearing conditions
-Collect same measures across season, as in free-living studies
-We expect to document genetic change underlying phenotypic divergence.
Microarray study to identify important loci...
-Construct cDNA library
-Sacrifice individuals during peak breeding from each free-living population
-Compare gene expression profiles
-Bayesian statistics to identify genes that differ
-Use molecular database to evaluate roles of genes that differ between populations
Conclusions• Utilizing a wide array of methods and techniques, we will
be able to assess the mechanisms underlying divergence in breeding phenology, hormonal, and immunological traits.
Broader Impacts:
-Train a diverse group of undergraduates, high-schoolers, and senior “citizen scientists,” in field and lab methods.
-Identify crucial physiological and genetic mechanisms that influence the ability of populations to persist in differing environments (e.g. global climate change, habitat destruction, disease epidemiological patterns)
-Dissemination of our results will include public outreach programs (e.g. “A Moment of Science,” Discovery Channel for Kids, National Geographic, Fox News’s “Nutty Professors”).