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Title: Standing variation rather than recent adaptive introgression probably underlies differentiation of the texanus subspecies of Helianthus annuus

The origins of geographic races in wide‐ranging species are poorly understood. In Texas, thetexanussubspecies ofHelianthusannuushas long been thought to have acquired its defining phenotypic traits via introgression from a local congener,H. debilis, but previous tests of this hypothesis were inconclusive. Here, we explore the origins ofH. a. texanususing whole genome sequencing data from across the entire range ofH. annuusand possible donor species, as well as phenotypic data from a common garden study. We found that although it is morphologically convergent withH. debilis,H. a. texanushas conflicting signals of introgression. Genome wide tests (Patterson'sDandTreeMix) only found evidence of introgression fromH. argophyllus(sister species toH. annuusand also sympatric), but notH. debilis, with the exception of one individual of 109 analysed. We further scanned the genome for localized signals of introgression usingPCAdmixand found minimal but nonzero introgression fromH. debilisand significant introgression fromH. argophyllusin some populations. Given the paucity of introgression fromH. debilis, we argue that the morphological convergence observed in Texas is probably from standing genetic variation. We also found that genomic differentiation inH. a. texanusis mostly driven by large segregating inversions, several of which have signatures of natural selection based on haplotype frequencies.

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Date Published:
Journal Name:
Molecular Ecology
Page Range / eLocation ID:
p. 6229-6245
Medium: X
Sponsoring Org:
National Science Foundation
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