Phylogeny of East Asian white pines

At this time (2021) there have been three noteworthy molecular studies of the east Asian white pines of subsection Strobus, using chloroplast, ribosomal, and mixed plastid gene markers (Syring et al. 2007, Yang et al. 2018, Zeb et al. 2019). Work to date provides reasonable confidence in the following statements, which rely heavily upon the analysis of Syring et al. (2007). That analysis incorporated both nuclear and chloroplast DNA sources and was probably the most extensive work to date, including 39 species in subgenus Strobus. The other cited analyses did little to contradict the analysis of Syring et al. (2007), but provided information about other taxa and in many ways confirmed the earlier study. The only taxa not addressed in these molecular studies are P. amamiana and P. cernua. Farjon (2010) allies P. amamiana to P. armandii, P. fenzeliana and P. morrisonicola, while Averyanov et al. (2014) suggest P. cernua is most closely related to P. fenzeliana and P. armandii.

P. bhutanica and P. wallichiana are sister species; the European P. peuce is sister to this pair.
P. dalatensis and P. fenzeliana are sister species.
P. kwangtungensis and P. wangii are sister species.
P. parviflora and P. sibirica, along with the European species P. cembra, are sister species.
A single clade unites P. amamiana, P. armandii, P. cernua, P. morrisonicola, and the P. dalatensis-fenzeliana and P. kwangtungensis-wangii species pairs.
P. koraiensis and P. pumila are embedded within a larger clade, basal to subsection Strobus, that includes the North American species P. albicaulis, P. lambertiana, P. monticola and P. strobus.

There are a two natural hybrids that inform these molecular results. The hybrid of P. pumila and P. sibirica is rare with only F1 introgression observed (Goroshkevich 2004), a result consistent with the relatively distant relationship of these species within subsection Strobus. Conversely, the hybrid of P. parviflora and P. pumila, P. × hakkodensis, is common, a result inconsistent with the remarks above, particularly since Syring et al. (2007) place P. sibirica and P. parviflora in the same clade. The placements by Syring et al. (2007) seem fairly robust, so perhaps this is an illustration of the reality that hybrid studies, like morphological studies, often fail to produce phylogenetic insights.

Citations

Averyanov, L. V., T. H. Nguyen, K. N. Sinh, T. V. Pham, V. Lamxay, S. Bounphanmy, S. Lorphengsy, L. K. Phan, S. Lanorsavanh, and K. Chantthavongsa. 2014. Gymnosperms of Laos. Nordic Journal of Botany 32(6):765–805.

Goroshkevich, Sergej N. 2004. Natural Hybridization between Russian Stone Pine (Pinus siberica) and Japanese Stone Pine (Pinus pumila). Pp. 169-171 in Breeding and genetic resources of five-needle pines: growth, adaptability, and pest resistance; 2001 July 23-27; Medford, OR, USA.

Syring, J., K. Farrell, R. Businský, R. Cronn, and A. Liston. 2007. Widespread genealogical nonmonophyly in species of Pinus Subgenus Strobus. Systematic Biology 56(2):163–181.

Yang, M.-Q., Y. Du, and L.-Z. Ling. 2018. Characterization of the complete chloroplast genome of Pinus wangii (Pinaceae), an endangered and endemic species in China. Mitochondrial DNA Part B 3(2):1195–1197 Available online at: https://www.tandfonline.com/doi/full/10.1080/23802359.2018.1519381; last accessed May 3, 2020.

Zeb, U., W. Dong, T. Zhang, R. Wang, K. Shahzad, X. Ma, and Z. Li. 2020. Comparative plastid genomics of Pinus species: Insights into sequence variations and phylogenetic relationships. J. Syst. Evol. 58(2):118–132.