ELECTRONIC SUPPLEMENTARY MATERIAL
Appendix S1: Predictors of inter-population hybrid fitness, statistical analysis and results
Methods
Reproductive population size, number of effective alleles (AE) and inbreeding coefficient (FIS)
for each of the 15 populations, and geographic, environmental, quantitative genetic (QST) and
molecular genetic (FST) distance matrices for each population pair were calculated as described
in Pickup et al. (2012). Population genetics statistics and variables for each population pair can
be found in the supporting information (Table S1). We used Mantel tests in the ‘ade4’ package in
R (Version 2.12.1) to examine the correlation among the four distance matrices, (i) geographic
distance, (ii) environmental distance, (iii) quantitative genetic distance (QST) and (iv) molecular
genetic distance (FST) and between the population characteristics (AE and FIS). The relation
between reproductive population size and AE and FIS was assessed using simple linear regression.
Results
The geographic distance matrix was significantly correlated with environmental distance
(r = 0.46, P = 0.029) and QST (r = 0.64, P = 0.0064), but not FST (r = -0.064, P > 0.05). We
found a significant correlation between QST and environmental distance (r = 0.61, P < 0.001)
while FST and QST were only marginally correlated (r = 0.44, P = 0.064). For the population
characteristics, reproductive population size (log) was significantly related to, but only explained
28% of the variance in the number of effective alleles (AE) (R2 = 0.28, P = 0.025). In contrast, we
found no relation between reproductive population size (log) and the inbreeding coefficient (FIS)
(R2 = 0.02, P = 0.266) and there was no correlation between FIS and AE (r = 0.29, P = 0.289).
Table S1: Summary of the predictor variables for the 12 population pairs (Pop. pair) of Rutidosis
leptorrhynchoides. Geog.Dist is geographic distance among populations, HPS is home
population size, FPS is foreign population size, Env.Dist is environmental distance, QST is
quantitative genetic differentiation, FST is molecular genetic differentiation, AEF is the number of
effective alleles in the foreign population, FISH is the inbreeding coefficient of the home
population and FISF is the inbreeding coefficient of the foreign population.
Home Foreign
pop.
pop.
Pop.
pair
Geog.Dist
(km)
HPS
FPS
Env.Dist
QST
FST
A EF
FISH
FISF
LW
QB
LW-QB
0.69
1171
10000
1.75
0.019
0.051
6.79
0.183 0.161
SR
CC
SR-CC
1.59
69600
220
1.1
0.021
0.032
6.84
0.162 0.208
MA
BA
MA-BA
3.96
118
81
0.95
0.056
0.052
7.22
0.178 0.180
HH
MA
HH-MA
7.98
300
118
1.63
0.082
0.057
6.11
0.161 0.178
CR
LW
CR-LW
15.24
4000
1171
3.92
0.047
0.059
6.14
0.179 0.183
MJ
CF
MJ-CF
27.81
27626
210
3.07
0.102
0.105
4.48
0.219 0.103
RH
CF
RH-CF
34.81
3489
210
3.87
0.223
0.112
4.48
0.277 0.103
MJ
GB
MJ-GB
71.89
27626
95200
0.57
0.022
0.044
9.15
0.219 0.201
GB
PO
GB-PO
78.89
95200
8171
0.82
0.011
0.052
5.75
0.201 0.209
SR
TR
SR-TR
506.2
69600
626
2.64
0.113
0.040
8.57
0.162 0.189
CF
SA
CF-SA
516.01
210
137
4.05
0.336
0.102
8.11
0.103 0.113
GB
TR
GB-TR
586.17
95200
626
2.39
0.108
0.034
8.57
0.201 0.189
Table S2: Crossing design for the 12 population pairs (Pop. pair) of Rutidosis leptorrhynchoides used to examine progeny fitness over
multiple generations following inter-population hybridization.
Pop.
Control
F (home x
pair Pop. pair (home x 1
foreign)
no.
home)
F2
(F1 x F1)
BC (F1 x home)
BC (F1 x foreign)
F1 (LW x QB) x F1 (LW x QB)
F1 (LW x QB) x LW
F1 (LW x QB) x QB
F1 (SR x CC) x F1 (SR x CC)
F1 (SR x CC) x SR
F1 (SR x CC) x CC
F3
(F2 x F2)
BC (F2 x
home)
BC (F2 x
foreign)
F2 x F2
F2 x SR
F2 x CC
F2 x F2
F2 x HH
F2 x MA
F2 x F2
F2 x MJ
F2 x CF
1
LW-QB LW x LW LW x QB
2
SR-CC SR x SR
3
MA-BA MA x MA MA x BA
F1 (MA x BA) x F1 (MA x BA)
F1 (MA x BA) x MA
F1 (MA x BA) x BA
4
HH-MA HH x HH HH x MA F1 (HH x MA) x F1 (HH x MA)
F1 (HH x MA) x HH
F1 (HH x MA) x MA
5
CR-LW CR x CR CR x LW
F1 (CR x LW) x F1 (CR x LW)
F1 (CR x LW) x CR
F1 (CR x LW) x LW
6
MJ-CF MJ x MJ
MJ x CF
F1 (MJ x CF) x F1 (MJ x CF)
F1 (MJ x CF) x MJ
F1 (MJ x CF) x CF
7
RH-CF RH x RH RH x CF
F1 (RH x CF) x F1 (RH x CF)
F1 (RH x CF) x RH
F1 (RH x CF) x CF
8
MJ-GB MJ x MJ MJ x GB
F1 (MJ x GB) x F1 (MJ x GB)
F1 (MJ x GB) x MJ
F1 (MJ x GB) x GB
9
GB-PO GB x GB GB x PO
F1 (GB x PO) x F1 (GB x PO)
F1 (GB x PO) x GB
F1 (GB x PO) x PO
F2 x F2
F2 x GB
F2 x GB
10
SR-TR
SR x SR
SR x TR
F1 (SR x TR) x F1 (SR x TR)
F1 (SR x TR) x SR
F1 (SR x TR) x TR
F2 x F2
F2 x SR
F2 x TR
11
CF-SA
CF x CF
CF x SA
F1 (CF x SA) x F1 (CF x SA)
F1 (CF x SA) x CF
F1 (CF x SA) x SA
12
GB-TR GB x GB GB x TR
F1 (GB x TR) x F1 (GB x TR)
F1 (GB x TR) x GB
F1 (GB x TR) x TR
SR x CC
Figure S1: The difference in the percent seedling survival between the control (within home
population progeny) and F2 as a function of the inbreeding coefficient of the foreign population
(FISF) and environmental distance (EnvD) among populations. Values above the dashed
horizontal (zero) line represent heterosis and below represent outbreeding depression. The
equation for this relation is: survival = 15.8 – 55x FISF + 2.5xEnvD; R2 = 0.39, P = 0.043.
Figure S2: The difference in the mean number of inflorescences between the control (within
home population progeny) and backcrosses to the home population (BCF1xH) as a function of
molecular genetic distance (FST) and environmental distance (EnvD) among populations. Values
above the dashed horizontal (zero) line represent heterosis and below represent outbreeding
depression. The equation for this relation is: no. inflor = 22.1 – 864x FST + 17.7xEnvD; R2 =
0.58, P = 0.008.
Figure S3: The average membership of the 15 populations of Rutidosis leptorrhynchoides to the
three genetic clusters (K = 3) identified by STRUCTURE analysis (Pritchard et al. 2000). For
details of the STRUCTURE analysis see (Pickup et al. 2012).
The distance between populations in Figure S3 indicates differences in the average genetic
composition of each population based on the three genetic clusters identified by STRUCTURE
analysis. Proximate populations in figure S3 have a similar average membership to the three
genetic clusters, while distant populations are more dissimilar in their average membership to the
three genetic clusters, indicating greater differences in genetic composition. For our data
regarding the consequences of inter-population hybridization for progeny fitness, differences in
average membership to the three genetic clusters may indicate the potential for heterosis.
Progeny from matings among populations with similar average membership to the three genetic
clusters may be expected to show less heterosis then populations that are more distant. However,
in our study we found that heterosis was absent in population pairs with very different genetic
composition based on the three genetic clusters (e.g. the number of inflorescences for F1 progeny
in population pairs HH-MA and MJ-CF). Therefore, for these populations, low heterosis
following inter-population hybridization is more likely the result of the genetic characteristics of
the foreign source population (i.e. the effective number of alleles), rather than genetic similarity.
References
Pickup M., Field D.L., Rowell D.M. & Young A.G. (2012). Predicting local adaptation in
fragmented plant populations: implications for restoration genetics. Evol. Appl., doi:
10.1111/j.1752-4571.2012.00284.x.
Pritchard J.K., Stephens M. & Donnelly P. (2000). Inference of population structure using
multilocus genotype data. Genetics, 155, 945-959.