Table 3 Summary of transmission ratio distortion loci and tests of different transmission ratio distortion mechanisms for the S. aethnensis × S. chrysanthemifolius F2 genetic mapping family

From: Interspecific crossing and genetic mapping reveal intrinsic genomic incompatibility between two Senecio species that form a hybrid zone on Mount Etna, Sicily

Linkage group

Reference marker

Map position (c M)

Late-acting sufficient

Asymmetric

Pre-zygotic

Heterozygote

Epistasis (minority genotype)

AC1 cluster

EC296

0.0

No

No

aeth

Yes

No

AC3 singleton (proximal)

E1M3_147

0.0

Yes

No

—

—

AC3 central (CA), AC6 (CD)

AC3 singleton (central)

S20

24.3

No

chrys

chrys

No

AC3 proximal (AC), AC3 distal (AC), AC6 (AC)

AC3 cluster (distal)

E5M3_405

36.5

Yes

chrys

—

—

AC3 central (CA), AC6 (DC)

AC4 singleton

E1M5_215

0.0

No

No

—

—

No

AC6 singleton

E1M5_131

41.7

No

No

—

—

AC3 proximal (DC), AC3 central (CA), AC3 distal (CD)

AC7 cluster (central)

E1M5_269

12.5

No

No

—

—

No

AC9 singleton

E1M5_132

15

No

chrys

—

—

No

AC10A cluster

EC290

3.4

No

aeth

aeth

No

No

AC5Ba singleton

ES25

0.0

—

aeth

—

—

—

AC10Ba singleton

S26

0.0

—

No

aeth

No

—

  1. Abbreviations: TRD, transmission ratio distortion; TRDL, transmission ratio distortion loci.
  2. Linkage group names correspond to Figure 1. Cluster or singleton refers to whether a cluster or a single marker within 10 cM was observed to exhibit genotypic TRD.
  3. The ‘reference marker’ is the marker with strongest TRD where a cluster of distorted markers was observed. ‘Late-acting sufficient’ tests if selective removal of the minority genotype according to observed post-mortality and reproductive failure would be sufficient to explain observed TRDLs. ‘Asymmetric’ tests if subsets of the mapping family divided according to parental cytotype showed asymmetric TRD in one cross direction only with ‘aeth’ and ‘chrys’ indicates if asymmetric TRD was observed in an S. aethensis or S. chrysanthemifolius cytoplasmic background, respectively. ‘Pre-zygotic’ tests for allelic TRD with ‘aeth’ and ‘chrys’ indicating the parental alleles showing significant deficiencies and ‘—’ indicating that no suitable codominant markers were available for testing at this TRDL. ‘Heterozygote’ tests for significant excesses or defiencies in heterozygosity of genotypes scored according to parental allelic state with ‘—’ indicating that no suitable codominant markers were available for testing at this TRDL. ‘Epistasis’ tests for non-independence of paired TRDL reference marker genotypes, with significantly interacting TRDLs listed. Letter codes in parentheses indicate minority genotype for the reference TRDL followed by the interacting TRDL. Genotype codes: A, homozygous S. aethnensis alleles; C, not homozygous for S. aethnensis alleles; D, not homozygous for S. chrysanthemifolius alleles.
  4. aIndicates that the last two TRDLs were only observed when specific mechanisms were investigated, so are not presented in Figure 1 or counted as primary TRLDs in the text.
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