Caryopteris incana, an endangered species distributed parts of western
Kyushu in Japan, is composed of clusters of individuals that can be
recognized as a population, and grow in a spatially isolated
environment. The objective of this study was to evaluate the phenotypic
variation of C. incana in western Kyushu and to clarify their
relationships with natural environment and geographical structure,
therefore, we investigated the growth survey using collected seeds under
the same cultivation conditions. As a result, it was confirmed that each
natural population showed various phenotypes in plant height, flower
color, etc., and each population was classified into five groups by
phenotype, showing the similar phenotype in each region. On the other
hand, since different phenotypic groups were shown in the same region,
it was inferred that each natural population acquired various phenotypes
by differentiating independently in various natural environments. In
addition, chloroplast DNA haplotypes differed between populations with
the same phenotype, suggesting that they should be conserved as separate
local populations to maintain genetic diversity. Similarly, because of
the low seed-dispersal ability and the ecology as a lithophyte, even if
haplotypes are common, when phenotypes differ between populations, they
should be conserved as finely divided as possible. These results suggest
that local populations and their ranges of high conservation priority
should be set not only among regions but also within regions, and prompt
actions should be taken.