Table 2

All hybrid crosses with pairwise genetic distances (uncorrected p-distance calculated from mitochondrial D-loop sequences), divergence times (in millions of years based on two different relaxed molecular clocks and the internally calibrated clock) and phenotypic shape differentiation based on Mahalanobis distances.

Cross type

Species crossed

Genetic distance

Divergence

time

internal clock

(lower-upper bound)

Divergence time

fossil record

Divergence time Gondwana break-up

Phenotypic distance

% T_total

Transgressive families (%)

% T_total

Transgressive families (%)

F1 hybrids

F2 hybrids

1

N. omni × P. pun

0.007¹

0.35-0.61

0.10

0.14

5.69

12.55

75

14.73

100

2

P. chil × P. ny

0.007¹

0.35-0.61

0.10

0.14

13.23

30.76

100

6.42

80

3

P. rock × P. pun

0.007¹

0.35-0.61

0.10

0.14

3.95

32.48

100

-

-

4

M. est × A. call

0.0188

0.93-1.64

0.58

0.92

16.19

0.14

37.5

18.20

71.4

5

P. taen × A. call

0.0241

1.19-2.1

0.89

1.49

19.29

3.71

100

14.40

100

6

A. burt × A. call

0.0408

2.02-3.56

2.23

4.12

22.12

5.58

50

39.07

100

7

P. ny × A. call

0.0553

2.74-4.82

3.78

7.43

7.09

13.9

62.5

32.46

75

The total amount of transgression (T_total) occurring on the major axes of phenotypic shape variation is shown separately for F1 and F2 hybrids. Also reported is the proportion of transgressive families obtained per cross type (i.e. the number of families containing transgressive phenotypes divided by the total number of families of that cross type).

¹Note that these distance estimates are likely overestimates of genetic distance between species. Distances are based on sequence differences between mitochondrial D-loop haplotypes, but these species have highly incomplete haplotype lineage sorting. Hence any distance obtained from a small sample of sequences is likely to overestimate species distance

Stelkens et al. BMC Evolutionary Biology 2009 9:283   doi:10.1186/1471-2148-9-283