5 Conclusions
Differences in temperature and daylength were found between early and
late rice-cultivation seasons in Leizhou, with a lower temperature and
longer daylength in the early seasons than those in the late seasons.
These findings indicated that some stressful ecological elements, which
can affect weedy rice growth and development, probably present in the
early rice-cultivation seasons. In addition, significant differences in
plant heights, the number of tillers per plant, flowering time, and
reproductive traits were detected between the early- and late-season
weedy rice populations occurring in the same rice fields in the early
rice-cultivation season, and the early-season populations showed evident
growth and development advantages than the corresponding late-season
populations. Noticeably, such phenotypical divergence was associated
with the local adaptation in the early-season weedy rice populations,
suggesting that the adaptive evolution had taken place in weedy rice
populations. Altogether, findings of this study provided solid evidence
of phenotypic divergence between the sympatric early- and late-season
weedy rice populations, likely associated with the local adaptation to
their ambient temperature and photoperiod.