Evolution of the Genus Camellia Based on the Biological Interaction and the Historical Background

概要

Invited Talk
Invited Talk 1

Evolution of the Genus Camellia
Based on the Biological Interaction and the Historical Background
Harue ABE1, Saneyoshi UENO2, Ayumi MATSUO3, Shun K. HIROTA4, Hiroki MIURA5, Monghuai SU6,
Yunguang SHEN7, Yoshihisa SUYAMA8 and Zhonglang WANG7
1

Niigata Univ.
2
Affrc
3
GENODAS
4
Osaka Metropolitan Univ.
5
Aquarium Asamishi
6
Chinese Culture Univ.
7
Kunming Botanical Garde
8
Tohoku Univ.

The genus Camellia (Theaceae) is particularly prevalent in East and Southeast Asia (82-280 species). According to the Flora
of China, there are 13 species in the sect. Camellia, of which 12 are found in China (11 being endemic), and only two species, C.
japonica and C. rusticana, are found in Japanese islands. Since these two species are distributed at the northern limit of the genus
Camellia, it is thought to have come from the continent and have speciated in Japan. Comparing the morphology, most species
of Camellia have separated flower filaments, but the sect. Camellia species except for C. rusticana and C. chekiangoleosa have
connected filaments, which indicates the bird-pollinated flower characteristics to keep a large amount of nectar. C. japonica blooms
in the winter when insects are absent and must depend on bird pollination whereas other Camellias depend on both pollination,
insects and birds. Therefore C. japonica might be the most adaptable species for bird pollination. On the other hand, C. rusticana
has ancestral traits with not-connected filaments in the sect. Camellia. We hypothesized that the pollinator shift from insects to birds
may have caused speciation from the ancestral genus Camellia to the sect. Camellia. Later, C. rusticana might get back to insect
pollination to fit the snowy environment in Japan. Hence, this study aims to examine the speciation of Japanese Camellias based on
pollinator shift by comparing the floral morphologies and the genetic differentiation of the genus Camellia. Next, we examined the
demographic history of C. japonica, which is widely distributed in the Japanese archipelago, the Korean peninsula, and the coastal
areas of mainland China and Taiwan. Through the above examinations, we discuss the evolution of the genus Camellia in Japan based
on biological interaction and the historical background.
We compared their morphologies of leaf hypodermis, flower form, petal color, filament color, and filament color in the twenty
populations and estimate quantitatively the differentiation. In the results, PCA analysis clearly distinguished between these species,
and both petal and filament colors were also statistically different between these species. The floral traits of C. japonica such as
filament connection rates, nectar, and sugar contents are one of the most adapted characteristics for bird pollination. The eight cpSSR
and the genome-wide SNPs by MIG-Seq revealed largely congruent results indicating that the genetic structures are divided into 3;
southern and northern C. japonica, and C. rusticana. The relationship between the three species including the related species in China
was further inferred from the phylogeny generated by RAxML using SNP data. It was found that C. chekiangoleosa is the ancestral
species and that C. rusticana and C. japonica are more related. However, demographic analysis, discussed below, reveals that the
divergence date between C. rusticana and C. japonica is also older. The intraspecific genetic structure of C. japonica was investigated
using ADMIXTURE 1.3.0, and the populations were divided into (1) mainly northern and (2)
mainly southern populations in the Japanese archipelago, (3) Chinese and Korean populations, and
(4) Okinawa and Taiwanese populations. Demographic analysis using DIYABC was carried out on
the four populations in which hybrid individuals were excluded by ADMIXTURE predicted that
the northern Japanese populations firstly differentiated from the southern Japanese populations, and
then the Okinawa and Taiwan populations differentiated. Later, the Chinese and Korean populations
returned to the mainland (the continent) from the southern Japanese populations. This result is
consistent with the results of ENM. The optimum distribution of C. rusticana during the last glacial
period was almost the same as that of the present distribution on the Sea of Japan, suggesting that
C. rusticana is a relict species in Japan since before the glacial period. The northern population is
the ancestral group as a relict in Honshu Japan. The results of this study could provide not only the
evolutionary history of the species but also the population priorities that should serve as the focus
Photo. White-eye feeding on
for future management and conservation of these species. ...

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