Rosa Rubicondior: Refuting Creationism - How Camellias Evolved As The Japanese Islands Formed

Camellia Rusticana

How Camellias evolved with the formation of the Japanese archipelago? | News | NIIGATA UNIVERSITY

It's a basic principle of evolution that environmental changes drive evolution by isolating populations which are then free to evolve on their own trajectory, and by creating new ecological niches into which species can diversify.

An almost perfect example of this in progress can be seen in the Camellia group of plants, of which one, tea, Camellia cinensis is perhaps the most important economically, But several others are also important cultivated garden plants with bright red, pink or white flowers.

Another phenomenon of evolution that this group of plants displays is that evolution is not a sudden event but a slow process over time, during which hybridization and gene flow between related species occurs until barriers to hybridization have evolved.

This tendency to form hybrids and the general similar morphologies has made accurate classification of the different species, and subspecies difficult and a matter of debate among taxonomists and botanists.

Now work by a team led by Dr. Harue Abe of Niigata University, Sado, Niiagata, Japan have shown how the evolution and distribution of this genus was strongly influenced by the formation of the Japanese archipelago.

The Camellia genus of plants. The Camellia genus is a group of flowering plants in the family Theaceae, commonly known as the tea family. Below is an overview of its taxonomy and key features:

Taxonomy

Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Ericales
Family: Theaceae
Genus: Camellia
General Characteristics

Native Range:

Camellias are native to eastern and southern Asia, particularly China, Japan, Korea, Vietnam, and India.

Species Diversity:

There are over 250 species in the genus Camellia. The most well-known include:

Camellia sinensis: The tea plant, used to produce green, black, and oolong tea.
Camellia japonica: Known for its ornamental value and large, showy flowers.
Camellia sasanqua: Often used in gardens for its fragrant flowers and adaptability.
Camellia reticulata: Renowned for its large and vibrant flowers.

Morphology:

Leaves: Evergreen, simple, alternately arranged, and serrated. They are glossy and leathery.
Flowers: Large and showy, with five to nine petals, often in shades of white, pink, or red. Some species have double flowers.
Fruits: Dry capsules containing seeds.

Ecology:

Camellias thrive in acidic, well-drained soils and prefer partial shade. They are commonly found in forest understories.

Economic Importance:

Camellia sinensisis economically significant as the source of tea.
Many species, such as Camellia japonica and hybrids, are prized as ornamental plants.

Cultural Significance:

Camellias hold cultural importance in countries like Japan and China, symbolizing virtues such as purity, perseverance, and elegance.

Taxonomic Challenges

The taxonomy of Camellia is complex due to the high level of hybridization and variation among species. Some species are poorly defined, and there is ongoing debate among botanists about the classification of certain groups.

The team's work is reported, open access, in the journal Ecology and Evolution and described in a news release from Niiagata University:

How Camellias evolved with the formation of the Japanese archipelago?
Tracing the demographic history of Camellia japonica and Camellia rusticana
The distribution of plants has been shaped by geological and climatic changes over time through repeated migration, extinction, and adaptation to new environments. The genus Camellia, comprising over 100 species mainly in East Asia, is a representative warm-temperate tree of the Sino-Japanese Floristic Region.

In Japan, four species of Camellia are found, with Camellia japonica and Camellia rusticana being the most well-known. C. japonica has a broad distribution from Aomori Prefecture in the cool-temperate zone to subtropical Taiwan and the coastal regions of China, suggesting its high adaptability to different climates. In contrast, C. rusticana is a Japan Sea element plant adapted to heavy snowfall areas. Plants categorized as Japan Sea elements are generally thought to have evolved from closely related species on the Pacific side, and C. japonica and C. rusticana were also believed to follow this pattern. Following this idea, C. rusticana was hypothesized to have diverged from C. japonica as an adaptation to snow-covered environments. However, this hypothesis had not been fully tested scientifically. This study aimed to clarify the evolutionary history of these two species by analyzing their distributional changes using genetic analyses and ecological niche modeling.

Phylogenetic analyses revealed clear differentiation among C. japonica, C. rusticana, and C. chekiangoleosa, a closely related continental species. Their common ancestor is estimated to have diverged approximately 10 million years ago during the Late Miocene, coinciding with the separation of the Japanese archipelago from the continent. This suggests that the two species diverged simultaneously due to geographic isolation, contradicting the previous hypothesis that C. rusticana evolved from C. japonica in response to Quaternary glacial cycles.

The Studied Camellias and Dr. Harue Abe

The populations of C. japonica are divided into three major groups: northern Japan, southern Japan (including mainland China and Korea), and the Ryukyu-Taiwan region. Among them, the northern population is particularly distinct from the others. Tracing their evolutionary history, analyses revealed that the southern population diverged from the northern population about 3.3 million years ago, followed by the Ryukyu-Taiwan population splitting from the southern population 1.8 million years ago, and finally, the continental population (including Korea) diverging from the southern population 27,000 years ago. These findings indicate that C. japonica, which originally migrated from the continent to the Japanese archipelago, later evolved and eventually recolonized the continent (reverse colonization). This provides key evidence that islands are not evolutionary dead ends but can serve as sources of genetic diversity for continental populations.

Publication:
Harue Abe, Saneyoshi Ueno, Ayumi Matsuo, Shun K Hirota, Hiroki Miura, Mong-Huai Su, Yun-Guang Shen, Yoshihiko Tsumura, Yoshihisa Suyama, Zhong-Lang Wang
Evolutionary histories of Camellia japonica and Camellia rusticana
Ecol Evol 14: e70721. https://doi.org/10.1002/ece3.70721

ABSTRACT
The genus Camellia is widely distributed, primarily in East Asia. Camellia japonica is located at the northern limit of this genus distribution, and understanding changes in its distribution is crucial for understanding the evolution of plants in this region, as well as their relationship with geological history and climate change. Moreover, the classification of sect. Camellia in Japan has not been clarified. Therefore, this study aims to understand the evolutionary history of the Japanese sect. Camellia. The genetic population structure was analysed using SNP data and MIG-seq. The relationship between the Japanese sect. Camellia, including the related species in China, was further inferred from the phylogeny generated by RA x ML, SplitsTree and PCA. Population genetic structure was inferred using a Bayesian clustering method (ADMIXTURE). We subsequently employed approximate Bayesian computation, which was further supported by the coalescent simulations (DIYABC, fastsimcoal and Bayesian Skyline Plots) to explore the changes in population, determining which events appropriately explain the phylogeographical signature. Ecological niche modelling was combined with genetic analyses to compare current and past distributions. The analyses consistently showed that C. japonica and C. rusticana are distinct, having diverged from each other during the Middle to Late Miocene period. Furthermore, C. japonica differentiated into four major populations (North, South, Ryukyu-Taiwan and Continent). The Japanese sect. Camellia underwent speciation during archipelago formation, reflecting its ancient evolutionary history compared with other native Japanese plants. C. rusticana did not diverge from C. japonica in snow-rich environments during the Quaternary period. Our results suggest that both species have been independent since ancient times and that ancestral populations of C. japonica have persisted in northern regions. Furthermore, the C. japonica population on the continent is hypothesised to have experienced a reverse-colonisation event from southern Japan during the late Pleistocene glaciation.

1 Introduction
Theaceae family comprises approximately 28 genera and 600 species, predominantly distributed in humid temperate regions (Nagamasu 2006). Camellia is a pivotal genus identified in the Sino-Japanese Floristic Region (SJFR) of East Asia, with approximately 120 species distributed in East and Southeast Asia. The Sino-Japanese floristic region (SJFR) is renowned for its high levels of biodiversity and endemism, primarily attributed to its complex climatic history and varied topography. This region has served as a refuge during past climatic fluctuations, facilitating the survival and diversification of many plant species (e.g., Lu et al. 2020; Qiu, Fu, and Comes 2011; Takahashi et al. 1994). The historical biogeography and climate change relationships of Camellia have been investigated (e.g., Zan et al. 2023); however, the evolutionary history of sect. Camellia in Japan remains unexplored. Investigations for the molecular phylogeny of sect. Camellia species in their northernmost limit of distribution in Japan are warranted to comprehend the evolution, climate change association and prospective conservation of temperate forest tree species.

The Camellia section Camellia characteristically features strikingly aesthetic large red petals adapted for bird pollination. The seeds are primarily dispersed by gravity, with secondary dispersal by animals, particularly rodents (Abe et al. 2006.1). The Japanese species Camellia japonica possesses multiple horticultural cultivars. The divergence of C. japonica from C. chekiangoleosa is estimated to have occurred within a timeline ranging from approximately 10 to 17 Ma (Cheng et al. 2022; Yan et al. 2021; Rao et al. 2018). This implies that C. japonica differentiated from its Eurasian relatives during the Japanese archipelago formation. Elucidating the demographic history of this northernmost Camellia species in temperate forests is essential for predicting plant dispersal in response to geographical events and climate change in Japan. For example, the genetic differentiation of organisms, divided by the Fossa Magna on Honshu, highlights the geological and biological distribution alterations in the Japanese archipelago. Quaternary climatic fluctuation studies have provided phylogeographic insights into glacial refugia, colonisation routes and range expansion (Dumolin-Lapègue et al. 1997; Gonzales, Hamrick, and Chang 2008; Ikeda and Setoguchi 2007; McLachlan et al. 2007.1; Petit et al. 2003). Nonetheless, the quaternary expansion–contraction model remains controversial, with recent research supporting ‘cryptic (or micro-) refugia’ at higher latitudes (Provan and Bennett 2008.1; Rull 2009). Quaternary climate shifts and the associated environmental modifications have facilitated range fragmentation, vicariance and population isolation, thereby fostering allopatric (incipient) speciation through selection and genetic drift (Comes, Tribsch, and Bittkau 2008.2; Yesson, Toomey, and Culham 2009.1).

Camellia japonica and C. rusticana from sect. Camellia exhibits distinct natural distributions in Japan (Figure S1). C. japonica is predominantly localised in the warm coastal regions of the Ryukyu Islands, Kyushu, Shikoku and Honshu (Horikawa 1972) and Taiwan, South Korea and the coastal areas of mainland China (Nagamasu 2006). Conversely, C. rusticana occurs in the snow-clad regions by the Sea of Japan side, from Shiga to Akita Prefecture, earning it the nickname ‘snow Camellia’. Owing to variations in habitats and morphologies (e.g., Ishizawa 1988; Tsuyama 1956), these species are disparately categorised by researchers, causing taxonomic uncertainty stemming from known hybridisation in adjacent habitats (Ueno, 2009.2). Tsuyama (1956, 1988.1) suggested that the ‘snow Camellia’ presumably adapted and underwent speciation from a temperate climate to frigid environments, as closely related species are distributed in the warm temperate zone along the Pacific Ocean (Sakai 1982). Two varieties of Daphniphyllum macropodum genetically support the aforementioned adaptation (Yoichi et al. 2023.1). However, conflicting findings have emerged from prior studies comparing the molecular phylogenies of C. japonica and C. rusticana. PCR-restriction fragment length polymorphism analyses revealed standard bands between C. chekiangoleosa and C. rusticana, whereas C. japonica exhibited disparate patterns (Tanikawa et al. 2008.3). Vijayan, Zhang, and Tsou (2009.3) positioned C. chekiangoleosa as holding an ancestral position within the same clade relative to C. japonica and C. rusticana, which are identified as closely related species from the continent. Zhao, Hodkinson, and Parnell (2022.1) did not include C. rusticana; nonetheless, C. chekiangoleosa was positioned as a sister species to C. japonica in their broader phylogenetic analysis of the Camellia section. Molecular phylogenetic studies on Camellia depicted speciation within the sect. Camellia predates the glacial period, with its origin and diversification occurring 6–30 million years ago (Ma) during the Miocene epoch (Cheng et al. 2022; Qin et al. 2023.2; Rao et al. 2018; Wu et al. 2022.2; Zan et al. 2023; Zhang et al. 2014, 2022.3; Zhao, Hodkinson, and Parnell 2022.1). These uncertainties warrant subsequent analyses involving ancestral Eurasian species, which are crucial for delineating the migration time of the sect. Camellia in Japan and their speciation timing and processes in a geohistorical context (Abe, Miura, and Katayama 2023.3); nevertheless, their precise evolutionary relationships remain ambiguous.

Based on the above background, this study aims to analyse the demographic history of C. japonica and C. rusticana and clarify the impact of geological history and climate change on their distribution and evolution. This will highlight the importance of preserving the genetic diversity of the sect. Camellia in Japan.

Abe, H., Ueno, S., Matsuo, A., Hirota, S.K., Miura, H., Su, M.-H., Shen, Y.-G., Tsumura, Y., Suyama, Y. and Wang, Z.-L. (2024)
Evolutionary Histories of Camellia japonica and Camellia rusticana.
Ecol Evol, 14: e70721. https://doi.org/10.1002/ece3.70721

Copyright: ©2025 The authors.
Published by John Wiley & Sons. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

What this work makes abundantly clear is that the diversity and distribution of Japanese camellias are not historical accidents or static “created kinds”, but the predictable outcome of evolutionary processes operating over deep time. As the Japanese archipelago fragmented, shifted, and re-connected in response to plate tectonics and sea-level change, plant populations were repeatedly isolated, reunited, and reshaped. The genetic signatures of these events are still written into the camellias themselves, allowing researchers to reconstruct a detailed evolutionary history that mirrors the geological history of the islands on which they grow.

This is precisely what the Theory of Evolution predicts. Long-term geographic isolation produces divergence; secondary contact produces admixture; and changing environments favour different traits at different times. None of this requires special pleading, ad hoc explanations, or appeals to mystery. Instead, a coherent and testable evolutionary framework explains both the timing and the pattern of diversification observed in Japanese camellias, linking molecular phylogenies directly to independently established geological timelines spanning millions of years.

By contrast, the idea that these plants were spontaneously created a few thousand years ago fares poorly against the evidence. A recent, instantaneous origin cannot account for the deep genetic splits between lineages, the correspondence between divergence times and tectonic events, or the complex biogeographic patterns that only make sense in the context of a dynamically evolving archipelago. To accept such a notion would require dismissing not just evolutionary biology, but plate tectonics, palaeogeography, and molecular dating as well.

As so often in biology, the camellias of Japan tell a story that is both subtle and unambiguous: life changes, landscapes change, and the two are inseparably linked over vast spans of time. Far from undermining evolutionary theory, studies like this reinforce it, demonstrating once again that the living world makes sense only when viewed through the lens of deep time and descent with modification.

Advertisement

Amazon