Ecological speciation of a hybrid sunflower, Helianthus anomalus Yuval Sapir, Loren H. Rieseberg...
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Transcript of Ecological speciation of a hybrid sunflower, Helianthus anomalus Yuval Sapir, Loren H. Rieseberg...
Ecological speciation of a hybrid sunflower, Helianthus
anomalus
Yuval Sapir, Loren H. Rieseberg
Dept. of Biology, Indiana University,Bloomington, IN 47405, USA
Pre-/post-zygotic isolating barriers - reduce gene-flow.
Niche shift promotes genomic differentiation (selection).
Selection against unfit hybrid progeny (reinforcement).
Ecological speciation
= Speciation facilitated by divergent
selection in contrasting environments
Hybridization:
•Increases genetic variation and creates new combinations
•Complementary gene action
•Simultaneous change at multiple traits/genes
Role of hybridization in ecological speciation
If hybrid colonize different ecological habitat
Habitat-specific ecological selection promote hybrid speciation
Methods
• 96 individuals from each parental species (3 populations each)• 192 individuals from 4 populations of Helianthus anomalus• DNA extraction• Microsatellites markers from EST library• Preliminary survey 49 loci amplified in all 3 spp were chosen
Indices for detecting selection footprint
)2(
)1(lnln
popVAR
popVARRV
1)2(1
1
1)1(1
1
lnln 2
2
popH
popHRH
Schlötterer C., 2002. Genetics 160:753-763
Schlötterer C. & Dieringer, D., 2005. in: Nurminsky D. (ed) Selective Sweep. Landes Bioscience, Georgetown, TX, pp 55-64
Genetic diversity -
Genetic variance -
H =gene diversity = expected heterozigosity
Reduction in genetic variance or genetic diversity
Selective sweeps = hitch-hiking effect
Footprint of selection
Example from: Harr et al., 2002. PNAS 99(20):12949-12954
non-significant effect(95% interval)
significant reduction(P<0.05)
Locus lnRV ano/ann lnRV ano/pet lnRH ano/ann lnRH ano/pet lnRV ano/PSP lnRH ano/PSP
279 0.370063306 -0.582473871 0.616871722 -0.665118053 -0.33558 -0.19432
283 -3.959820226 -4.342449119 -4.624676908 -3.384418966 -4.17432 -4.28447
285 -0.201700483 -0.460701278 -0.091107944 -0.496282049 -0.39421 -0.59403
289 -1.082327545 -0.901026376 -2.392140467 -1.874146478 -0.99647 -2.4265
313 -0.353491339 -0.668690377 -0.972340453 0.7922876 -0.54449 -0.52819
317 -2.211069594 -2.213149476 -2.25805302 -1.799079708 -2.23718 -2.28374
321 0.515002212 -0.750125252 0.531176522 -0.613313962 -0.35225 -0.257
323 -0.177087018 -1.402019453 -0.09917793 -2.04257327 -0.96884 -1.07669
324 -1.291081689 -1.169741318 0.347214221 1.100793562 -1.23441 0.69088
356 -3.090069816 -1.568625393 -0.403263699 -0.26715323 -2.60808 -0.35278
382 -1.645997933 -2.138230301 -2.485190161 -2.715321614 -2.22197 -3.21965
424 -5.841082394 -5.752628469 -2.316011577 -2.533400084 -5.79674 -2.47042
426 0.904128942 -0.149556001 -0.012490882 -3.561364411 -0.00308 -2.17582
429 -1.34775602 -1.832156726 -0.34592679 -0.578370591 -1.67122 -1.30204
439 -2.727556354 -1.004600964 -2.025595886 -0.483410193 -2.43943 -2.01536
440 -2.231910445 -1.733416744 -2.377568129 -1.082526042 -2.04003 -2.43532
441 -3.265653326 -1.101263355 -0.78466602 -0.430370161 -2.77961 -0.73815
446 -4.885154939 -3.293560928 -3.331557892 -1.181931246 -4.50563 -2.58138
451 -0.526901367 0.102891354 -2.537209852 -3.050925384 -0.28008 -2.8457
459 -2.445276465 0.399010384 -1.660772719 -2.119456688 -1.8683 -2.22423
466 -2.798428392 -1.332973231 -1.574383794 -1.253664018 -2.58618 -2.26334
520 0.0122101 -0.188976128 -0.464936489 -0.034136815 -1.04396 -1.40242
536 -1.261861746 -2.066244116 0.264362191 -1.999019143 -1.83283 -1.33293
538 1.798784834 2.398645674 1.162760445 0.24347485 1.80622 -0.26914
540 -0.199616395 0.827318193 -0.369147716 -0.379104687 0.14808 -0.49121
541 -2.682534099 -3.098202516 -3.027836248 -4.274103908 -3.14006 -4.0106
595 0.471601821 0.688469857 -0.013263357 -1.595789278 0.51352 -1.96624
612 -0.276136693 -0.738612043 -0.795295327 -1.657499122 -0.87573 -1.82525
615 0.521900569 -0.177102153 -0.084882787 -0.328026906 0.08111 -0.51209
621 -0.864374377 -1.374634628 -0.075610784 -0.509381005 -1.17825 -0.52207
668 -0.780715628 -0.614952751 -2.997374904 -3.079441486 -0.85056 -3.44805
677 -1.238041458 -2.516353793 -0.736806034 -1.425133687 -2.06577 -1.11932
692 -1.911487283 -2.447325171 0.507665556 -0.618505211 -2.40762 -0.7656
701 -1.774588809 -2.347849394 -3.494156724 -2.209051038 -2.11067 -3.57664
715 -7.573484869 -8.495438799 -8.964794845 -9.52644981 -8.10658 -9.5255
716 -3.413981133 -4.219405945 0.013514175 -2.148381915 -3.90258 -0.8879
732 -3.215636315 -3.136654452 -0.94256986 -2.155353082 -3.18543 -1.86963
739 -2.584307071 -3.971471926 -1.53976839 -2.409974258 -3.44103 -1.9973
765 -3.233822114 -4.160246433 -2.845909362 -3.91960935 -3.74782 -3.54954
772 -2.721618745 -3.083268656 -0.951886552 -0.836050438 -2.88519 -0.97619
813 -4.27710209 -4.380146113 -1.560635087 -2.885146452 -4.31745 -2.13002
815 -1.692166716 -3.025941688 -1.302680114 -1.867084736 -2.46333 -1.67498
834 -3.129918282 -3.570995678 -2.080027201 -2.374887972 -3.33086 -2.24646
848 -0.515982271 -1.095057596 -1.230462474 -1.209710918 -0.80583 -1.35894
854 -1.087410062 -1.642350663 -5.896708133 -5.846963648 -1.35952 -6.24423
953 -5.105017897 -5.42942434 -7.086745021 -6.520438521 -5.24619 -7.04584
985 -2.970893202 -2.552517359 -0.878278244 0.625854692 -2.81222 -0.37285989 -1.833147039 -1.466087702 -1.218420058 0.544332327 -1.69181 -0.60376998 -6.05431568 -5.728273309 -2.656400129 -0.281287565 -5.96192 -1.92316
lnRVlnRHano/ann2218ano/pet2220ano/PSP2623
PSP = pooled data from Parental Species; ano = H. anomalus ; ann = H. annuus ; pet = H. petiolaris
12 loci showed significant effect in both allele variance and genetic diversity
Results
lnRV and lnRH distributionslnRV=difference in allele variance; lnRH=difference in gene diversity
r=0.561-10
-8
-6
-4
-2
0
2
-10 -8 -6 -4 -2 0 2
lnRV
lnR
H
Reduced gene diversity and shared alleles
a
jaia ffps ,, ,min
-10
-8
-6
-4
-2
0
2
0 0.2 0.4 0.6 0.8 1
Proportion of shared alleles
lnR
H
Gene function – locus HT424 as an example
lnRH = -2.47; 4 alleles in H. anomalus; 10 in parentsProportion of shared alleles: 0.85
Sequence:AACTTATACAATGTAGAGATATGGTTGTTCCAAAGAAGATTCAACGTAGTAATCCTTATGAAGAGCGTGTTCCTGTCGGATTGGCTATTGTTGCAGCAGTCATAGTTCGGTTACAGCTTGCAAATACTGCTGCTGGTGGAATTGAAACACATGTTGGTGGTTCTATGTTAGTTGATGTGGTTAACAGCTCGTGGCTGCAAGTTATTCTAGCCGGTGTTACTTGGTATCTCATTGGTCTGGCTGCGGTTGAGATTATAGCAGTCCTTCGAATAAAATCGAACGATATTGAAGAATGAATAAAATAGTATATATATACAGGTATGTAGTATGTATAGGTTAAGCTGTTATAGGAATCATATATTCATTATTATATACACTCTCGAAAGAAAGCTCAGTCAAGCGTATGTTCATTACCCCAAAAAAAATCTTTAAAGTCGGAACACAAAAAATGTCGGGGGAAAAAAAA
Putative translation:LIQCRDMVVPKKIQRSNPYEERVPVGLAIVAAVIVRLQLANTAAGGIETHVGGSMLVDVVNSSWLQVILAGVTWYLIGLAAVEIIAVLRIKSNDIEE*
BLAST results:DNAJ heat shock N-terminal domain-containing protein [Arabidopsis thaliana]
• Interact with heat-shock proteins• Can function as chaperones on their own• Role in targeting and folding of polypeptides• Regulation of gravitropism
Summary and conclusion:
• Twelve of 49 loci exhibited significant reduction in variation compared to both parental species.
• The proportion of shared alleles is correlated with reduced variation.
• Genes exhibit footprint of selection may contribute to drought tolerance, heat tolerance, or deepening the root.
• Selection on ecologically important genes allowed H. anomalus to colonize desert sand dunes.
Future directions
• Finer-scale hitch-hiking mapping to determine size of genomic regions affected by selective sweep
• Sequence analyses to confirm history of selection
• Functional analyses (correlations with QTLs, gene expression studies, transformations)
University of GeorgiaBeau BrouilletteLisa Donovan
ThanksRieseberg lab, IUAmanda PostoBriana Gross Nolan KaneRebecca RandelYoko KakugawaZhao Lai
$upported by:
BARD-Vaadia post-doctoral fellowship
University of Veterinary Medicine, ViennaChristian SchlöttererDaniel Dieringer