Geographic distance and latitude, but not environmental distance,
affect germination rate:
There was a significant, nonlinear effect of geographic distance between
source population and common garden at the HD garden, but this effect
depended on seed type (distance2 x seed type: P =
0.001; Fig. 4; Appendix B). Chasmogamous seed germination decreased
weakly as distance from garden increased, whereas cleistogamous seed
germination was greatest when sourced somewhat close to
(~125 km away) but not directly from the HD garden (Fig.
4). When modeled separately by seed type, however, the weak distance
effect for chasmogamous seeds became nonsignificant (distance: P = 0.30;
distance2: P = 0.80), whereas the effect remained
significant for cleistogamous seeds (distance2: P =
0.002). The overall trend appears to be similar at the HR garden,
although there were no significant effects of distance or
distance2 at that garden (Fig. 4; Appendix H, Table
2).
The first two principal components explained 74.1% of the variation in
the environmental data from source populations (Appendix F). However,
there was no significant effect of environmental distance between source
population and common garden on germination at either common garden
(Fig. 5; Appendix H, Table 3). Furthermore, there was no significant
correlation between geographic and environmental distances of source
populations (Appendix G).
The effect of source population latitude on germination depended on seed
type at HD (P = 0.023) but was not significant at HR (P = 0.267; Fig. 6;
Appendix H, Table 4). Higher latitude exhibited a slight positive effect
on germination for chasmogamous seeds but a negligible effect for
cleistogamous seeds at HD (Fig. 6).