Evolution of Floral Display Size in a Morning Glory Jennifer Lau –Michigan State U. Rick Miller...
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Transcript of Evolution of Floral Display Size in a Morning Glory Jennifer Lau –Michigan State U. Rick Miller...
Evolution of Floral Display Sizein a Morning Glory
• Jennifer Lau– Michigan State U.
• Rick Miller– Southeastern
Louisiana U.
• Mark Rausher– Duke University
Ipomoea purpurearoadside in Jalisco, Mexico
note beaker of “stuff” in background
• What is the pattern of selection on floral display size?
• Self-compatible, hermaphroditic plant
• Ipomoea purpurea, common morning glory
• Display size -- number of flowers open on a single day (morning)
Ipomoea purpureaSoybean field in NC, USA
• Pattern of floral presentation varies greatly among plant species
• mass flowering• extended flowering• allocation of limited
resources• why does floral
display size vary?Ipomoea pedicellaris in Oaxaca, Mexico
0
5
10
15
20
25
1 2 3 4 5 6 7 8 9 10
Flower number
Nu
mb
er o
f in
div
idu
als
Natural population of Ipomoea purpurea growing in a soybean field in North Carolina
80% flowered1-10 flowers
0
2
4
6
8
10
12
14
1 2 3 4 5 6 7 8 9 10
Flower number
Nu
mb
er o
f in
div
idu
als
Natural population of Ipomoea purpurea growing in a soybean field in North Carolina
22% flowered1-3 flowers
• Experimental results• Array manipulated to
have range of number of flowers
• Selection through male function favors smaller display size
Experimental array ofrandomly arranged genotypes of Ipomoea purpurea
• Experimental results• Array manipulated to
have range of number of flowers
• Selection through male function favors smaller display size
• How did we arrive at this result?
wi/ fi = 1.19 - 0.85 fi
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Flower number per plant/Proportion of total flowers
Male
fitn
ess
/flow
er
num
ber
2 8 14 20 26 32
Main result
• Dynamics of evolution of floral display size
• Display size and increased selfing through geitonogamy
• Display size and pollen export to other plants
• (Inbreeding depression)
Total pollenproduced
Pollenremoved
Outcrosspollen pool
Geiton.pollen pool
Male outcrosssuccess
Femaleselfingrate
Display size
Maleselfingsuccess
Totalmalefitness
Inbreedingdepression
Diagram ofdynamics ofevolution offloral display size
Developed byMark Rausher
Total pollenproduced
Pollenremoved
Display size
increasein displaysize
increased visitation
more pollenremoved
+
Total pollenproduced
Pollenremoved
Outcrosspollen pool
Geiton.pollen pool
Display size
increasedvisitation
increase ingeitonogamouspollen pool
increase inoutcrosspollen pool
Total pollenproduced
Pollenremoved
Outcrosspollen pool
Geiton.pollen pool
Display size
increase indisplay size
pollinators visitingmore flowers onsame plant withlarger display
great fraction togeitonogamouspollen pool
Total pollenproduced
Pollenremoved
Outcrosspollen pool
Geiton.pollen pool
Display size
great fraction togeitonogamouspollen pool
unavailable foroutcrossing
smaller fractionto outcross pollen pool
+ -
Total pollenproduced
Pollenremoved
Outcrosspollen pool
Geiton.pollen pool
Femaleselfingrate
Display size
Maleselfingsuccess
increasedgeitonog.
increasedfemale &male selfingsuccess
Total pollenproduced
Pollenremoved
Outcrosspollen pool
Geiton.pollen pool
Male outcrosssuccess
Femaleselfingrate
Display size
Maleselfingsuccess
fraction tooutcross pooldecrease withdisplay size
net effect onmale outcrosssuccess positiveor negative
Total pollenproduced
Pollenremoved
Outcrosspollen pool
Geiton.pollen pool
Male outcrosssuccess
Femaleselfingrate
Display size
Maleselfingsuccess
Totalmalefitness
Inbreedingdepression
Total malefitness issum of:
(1) male selfing success (-id)
(2) male outcrosssuccess
positive or negative
Total pollenproduced
Pollenremoved
Outcrosspollen pool
Geiton.pollen pool
Male outcrosssuccess
Femaleselfingrate
Display size
Maleselfingsuccess
Totalmalefitness
Inbreedingdepression
Empirical study:
Female selfingsuccess
Male outcrosssuccess
Total male fitness
• Array manipulated to have 2, 8, 14, 20, 26, 32 flowers
• 6 inbred lines randomly arranged
• 2 replicates/line32 8 14 26 20 2
8 32 2 26 20 14
Simplified diagram ofexperimental array
• Each array left for one day
• One treatment each day -- 6 days
• Capsules collected• One seed scored for 4
loci• Determine parentage
of each seed• 1224 flowers
monitored (thanks Jen)
• Assume total number of flowers produced by a plant over a season constrained
• Focus on:– Per-flower male selfing success– Per-flower outcross success– Per-flower total male fitness
• Used a likelihood analysis
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Flower number per plant/Proportion of total flowers (f)
Selfi
ng r
ate
2 8 14 20 26 32
Female selfing rate increased with number of flowers perplant -- expected with greater geitonogamy
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Flower number per plant/Proportion of total flowers
Outc
ross
succ
ess
/flow
er
num
ber
2 8 14 20 26 32
Plants with fewer flowers were more successful atfertilizing other plants -- than plants with many flowers
wi/ fi = 1.19 - 0.85 fi
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Flower number per plant/Proportion of total flowers
Male
fitn
ess
/flow
er
num
ber
2 8 14 20 26 32
,11
n
j jjiiii fsxfsw
wi/ fi = 1.19 - 0.85 fi
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Flower number per plant/Proportion of total flowers
Male
fitn
ess
/flow
er
num
ber
2 8 14 20 26 32
On a per-flower basis, significant negative relationshipbetween floral display size and male fitness
wi/ fi = 1.19 - 0.85 fi
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Flower number per plant/Proportion of total flowers
Male
fitn
ess
/flow
er
num
ber
2 8 14 20 26 32
Increased geitonogamous selfing is more than offset by disadvantage of decreased male outcross success
Conclusions
• Increased floral display size is generally accompanied by increased geitonogamous selfing
• Increased visitation and increased geitonogamy have opposite effects on outcross success
• Net effect determines whether selection through male fitness favors large or small displays
Lau, J. A., R. E. Miller, and M. D. Rausher. 2008.Selection through male function favors smaller floral display size in the common morning glory, Ipomoea purpurea (Convolvulaceae). American Naturalist. 172: 63-74.
• William & Joyce Childress• Chris Nacci • Anonymous reviewers• National Science Foundation
Acknowledgements