Diversification between islands and ecological radiation within islands are postulated to have occurred in the Euphorbia species (sect. Aphyllis subsect. Macaronesicae) on the Canary Islands. In this study, the biogeographical pattern of 11 species of subsect. Macaronesicae and the genetic differentiation among five species were investigated to distinguish the potential mode and mechanism of diversification and speciation. The biogeographical patterns and genetic structure were examined using statistical dispersal-vicariance analysis, Bayesian phylogenetic analysis, reduced median-joining haplotype network analysis and discriminant analysis of principal components. The gene flow between related species was evaluated with an isolation-with-migration model. The ancestral range of the species of subsect. Macaronesicae was inferred to be Tenerife and the Cape Verde Islands and Tenerife-La Gomera acted as sources of diversity to other islands of the Canary Islands. Inter-island colonization of E. lamarckii among the western islands and a colonization of E. regis-jubae from Gran Canaria to northern Africa were revealed. Both diversification between islands and radiation within islands have been revealed in the Euphorbia species (sect. Aphyllis subsect. Macaronesicae) of the Canary Islands. It was clear that this group began the speciation process in Tenerife-La Gomera and this process occurred with gene flow between some related species.

Kleinia neriifolia Haw. is an endemic species on the Canaian archipelago, this species is widespread in the coastal thicket of all the Canaian islands. In the present study, genetic diversity and population structure of K. neriifolia were investigated using chloroplast gene sequences and nuclear SSR (simple sequence repeat). The differentiation among island populations, the historical demography, and the underlying evolutionary scenarios of this species are further tested based on the genetic data. Chloroplast diversity reveals a strong genetic divergence between eastern islands (Gran Canaria, Fuerteventura, and Lanzarote) and western islands (EI Hierro, La Palma, La Gomera, Tenerife), this west-east genetic divergence may reflect a very beginning of speciation. The evolutionary scenario with highest posterior probabilities suggests Gran Canaria as oldest population with a westward colonization path to Tenerife, La Gomera, La Palma and EI Hierro, and eastward dispersal path to Lanzarote through Fuerteventura. In the western islands, there is a slight decrease in the effective population size towards areas of recent colonization. However, in the eastern islands, the effective population size increase in Lanzarote relative to Gran Canaria and Fuerteventura. These results further our understanding of the evolution of widespread endemic plants within Canarian archipelago.

Castanopsis sclerophylla (Lindl.) Schott. is a canopy tree species of evergreen broad-leaved forests in subtropical China. In this study, the genetic diversity and population structure of C. sclerophylla were investigated by using chloroplast DNA sequences and nuclear microsatellite markers. Permutation tests with chloroplast DNA sequences indicated the presence of phylogeographic structure in C. sclerophylla. Based on nuclear microsatellite markers, Bayesian clustering analysis revealed eastern-to-western differentiation in C. sclerophylla, and the analysis of molecular variance suggested population divergence has arisen along the Xuefeng, Luoxiao, and Wuyi mountain ranges. The approximate Bayesian computation demonstrated that the genetic diversity pattern of C. sclerophylla could be explained by geographic isolation followed by secondary contact. Ecological niche modelling showed that distribution of C. sclerophylla shrank southward at the Last Glacial Maximum and expanded northward at the Mid Holocene. These results suggested that the uplift of the Xuefeng, Luoxiao, and Wuyi mountain ranges and the interglacial–glacial climate change shaped the genetic diversity of C. sclerophylla. The Luoxiao mountain range should be considered as a key conservation unit of C. sclerophylla due to its higher level of genetic diversity. Our study supplies important information for prioritizing the conservation and sustainable utilization of C. sclerophylla, and provides insight on the dynamics of evergreen broad-leaved forests in subtropical China.

Castanopsis × kuchugouzhui Huang et Y. T. Chang was recorded in Flora Reipublicae Popularis Sinicae (FRPS) as a hybrid species on Yuelushan mountain, but it is treated as a hybrid between Castanopsis sclerophylla (Lindl.) Schott. and Castanopsis tibetana Hance in Flora of China. After a thorough investigation on Yuelushan mountain, we found a population of C. sclerophylla and one individual of C. × kuchugouzhui, but no living individual of C. tibetana. We collected C. × kuchugouzhui, and we sampled 42 individuals of C. sclerophylla from Yuelushan and Xiushui and 43 individuals of C. tibetana from Liangyeshan and Xiushui. We used chloroplast DNA sequences and 29 nuclear microsatellite markers to investigate if C. × kuchugouzhui is a natural hybrid between C. sclerophylla and C. tibetana. The chloroplast haplotype analysis showed that C. × kuchugouzhui shared haplotype H2 with C. sclerophylla on Yuelushan. The STRUCTURE analysis identified two distinct genetic pools that corresponded well to C. sclerophylla and C. tibetana, revealing the genetic admixture of C. × kuchugouzhui. Furthermore, the NewHybrids analysis suggested that C. × kuchugouzhui is an F2 hybrid between C. sclerophylla and C. tibetana. Our results confirm that C. × kuchugouzhui recorded in FRPS is a rare hybrid between C. sclerophylla and C. tibetana.