Cytotype Distribution and Chloroplast Phylogeography of Actinidia Chinensis Complex

Abstract

Background: Previous plant phylogeography in subtropical China mostly focused on rare and endangered species, whereas few studies conducted on the taxa with relatively wide distribution, especially for polyploid species. We used Actinidia chinensis complex, a widespread geographically woody liana of variable ploidy in subtropical China, to investigate its cytotype and haplotype distribution pattern based on three chloroplast fragments (ndhF-rpl132, ps16-trnQ and trnE-trnT). Macroevolutionary, microevolutionary and niche modeling tools were also combined to disentangle the origin and the demographic history of the species or cytotypes. Results: The ploidy levels of 3569 individuals from 128 populations sampled throughout the species distribution range were estimated using flow cytometry. The widespread cytotypes were diploids followed by tetraploids and hexaploids, while triploids and octaploids occasionally occurred in a few populations. Thirty-one chloroplast haplotypes were detected and the genetic diversity and genetic structure were great differences between the var. chinensis and var. deliciosa. Our results also revealed these two varieties (or ploidy races) inhabit significantly different climatic niche spaces. Ecological niche models (ENMs) indicate that all varieties’ ranges contracted during the Last Interglacial (LIG), and expanded eastward or northward during the Last Glacial Maximum (LGM). Conclusions: Pliocene and Plio-Pleistocene climatic fluctuations and vicariance may have played key roles in shaping the current population structure and historical demography in the A. chinensis complex. The polyploidization process also played an important role in the historical demography of the A. chinensis complex through improving their adaptability to environmental changes.