DOI: 10.5061/dryad.4bh26
title: Data from: Comparative linkage maps suggest that fission, not polyploidy, underlies near-doubling of chromosome number within monkeyflowers (Mimulus; Phrymaceae)

description: Changes in chromosome number and structure are important contributors to
 adaptation, speciation, and macroevolution. In flowering plants,
 polyploidy and subsequent reductions in chromosome number by fusion are
 major sources of chromosomal evolution, but chromosome number increase by
 fission has been relatively unexplored. Here, we use comparative linkage
 mapping with gene-based markers to reconstruct chromosomal synteny within
 the model flowering plant genus Mimulus (monkeyflowers). Two sections of
 the genus with haploid numbers {greater than or equal to} 14 have been
 inferred to be relatively recent polyploids because they are
 phylogenetically nested within numerous taxa with low base numbers (n =
 8-10). We combined multiple datasets to build integrated genetic maps of
 the M. guttatus species complex (section Simiolus, n = 14) and the M.
 lewisii group (section Erythranthe; n = 8), and then aligned the two
 integrated maps using &gt;100 shared markers. We observed strong
 segmental synteny between M. lewisii and M. guttatus maps, with
 essentially 1-to-1 correspondence across each of 16 chromosomal blocks.
 Assuming that the M. lewisii (and widespread) base number of 8 is
 ancestral, reconstruction of 14 M. guttatus chromosomes requires at least
 eight fission events (likely shared by Simiolus and sister section
 Paradanthus [n=16]), plus two fusion events. This apparent burst of
 fission in the yellow monkeyflower lineages raises new questions about
 mechanisms and consequences of chromosomal fission in plants. Our
 comparative maps also provide insight into the origins of a chromosome
 exhibiting centromere-associated female meiotic drive and create a
 framework for transferring M. guttatus genome resources across the entire
 genus.
description: Data for Composite Iron
 Mountain (CIM) M. guttatus linkage mapExcel files with the
 individual x marker genotype matrices for three F2 mapping populations.
 See readme file for more info on the mapping populations and linkage map
 generation.CIM
 matrices.zipIndividual x genotype
 matrices for BG4 and BN4 nearly isogenic line (NIL)
 populationsBoth NIL populations
 were derived from the inbred line cross of Sherar's Falls (SF)
 Mimulus nasutus and Iron Mountain 62 (IM62) M. guttatus. The BG4 and BN4
 lines started with IM62 x SF and SF x IM62 F1 hybrids, respectively,
 underwent 4 generations of backcrossing with the recurrent parent as
 pollen donor, and were made with single seed descent and no intentional
 selection. In both files, b = IM62 homozygote, a = SF homozygote, and H =
 heterozygote.NIL
 matrices.zipIndividual x genotype
 matrix for NIM2 F2 mapping population (SF M. nasutus x IM62 M.
 guttatus)Matrix of genotypes for
 second SF x IM62 F2 mapping population. b = IM62 homozygote, a = M.
 nasutus homozygote, h = heterozygote. Some markers with extreme
 transmission ratio distortion relative to flanking markers are included in
 dataset, but were removed during mapping. Plant growth conditions Seeds
 were planted in 2.25-in pots filled with Fafard 4P potting mix, watered,
 and stratified in the dark at 4°C for one week. Pots were then moved to
 the Duke University greenhouses and maintained under long-day photoperiod
 conditions (16 h light at 24°C / 8 h dark at 16°C) using supplemental
 high-intensity sodium lights (daytime PPFD &gt;750 mmol m-1 s-1). Light
 response curves indicate that this light level was near saturating for the
 plants (data not shown). We sowed approximately five seeds per pot, and
 thinned to the centermost individual after most seeds had germinated, two
 weeks after planting. While in the greenhouses, plants received weekly
 treatment with Peter’s Professional Blossom Booster 10-30-20
 fertilizer.NIM2_JoinMap.xls