Needle morphological evidence of the homoploid hybrid origin of Pinus densata based on analysis of artificial hybrids and the putative parents, Pinus tabuliformis and Pinus yunnanensis.

Wei Zhao,Hao Liu,Xiao-Ru Wang,Jianfeng Dai,Zhen Xing,Yue Li,Jian-Feng Mao,Fangqian Xing,Jingxiang Meng,Hua Zhang

doi:10.1002/ece3.1062

Wei Zhao, Hao Liu + Show 8 more

Open Access

https://doi.org/10.1002/ece3.1062

Copy DOI

Abstract

Genetic analyses indicate that Pinus densata is a natural homoploid hybrid originating from Pinus tabuliformis and Pinus yunnanensis. Needle morphological and anatomical features show relative species stability and can be used to identify coniferous species. Comparative analyses of these needle characteristics and phenotypic differences between the artificial hybrids, P. densata, and parental species can be used to determine the genetic and phenotypic evolutionary consequences of natural hybridization. Twelve artificial hybrid families, the two parental species, and P. densata were seeded in a high-altitude habitat in Linzhi, Tibet. The needles of artificial hybrids and the three pine species were collected, and 24 needle morphological and anatomical traits were analyzed. Based on these results, variations in 10 needle traits among artificial hybrid families and 22 traits among species and artificial hybrids were predicted and found to be under moderate genetic control. Nineteen needle traits in artificial hybrids were similar to those in P. densata and between the two parental species, P. tabuliformis and P. yunnanensis. The ratio of plants with three needle clusters in artificial hybrids was 22.92%, which was very similar to P. densata. The eight needle traits (needle length, the mean number of stomata in sections 2 mm in length of the convex and flat sides of the needle, mean stomatal density, mesophyll/vascular bundle area ratio, mesophyll/resin canal area ratio, mesophyll/(resin canals and vascular bundles) area ratio, vascular bundle/resin canal area ratio) relative to physiological adaptability were similar to the artificial hybrids and P. densata. The similar needle features between the artificial hybrids and P. densata could be used to verify the homoploid hybrid origin of P. densata and helps to better understand of the hybridization roles in adaptation and speciation in plants.

Highlights

Pinus densata is a pine species with a high-elevation niche, ranging from 2700 to 4200 m above sea level (a.s.l.) (Wu 1956; Guan 1981) in the southeastern region of the Tibetan Plateau
Openpollinated seeds from the six female clones were used as P. tabuliformis (Pt) samples, mixed seeds from the five pollen trees were used as P. yunnanensis (Py) samples, and mixed seeds from P. densata populations in Linzhi, Tibet, were used as P. densata (Pd) samples
All needle traits of hybrid families showed different variation ranges, and the variation ranges of NL, RCA, and mesophyll/resin canal area ratio (MA/RCA) nearly doubled

Summary

Introduction

Pinus densata is a pine species with a high-elevation niche, ranging from 2700 to 4200 m above sea level (a.s.l.) (Wu 1956; Guan 1981) in the southeastern region of the Tibetan Plateau. Molecular genetic analysis has supported that P. densata originated through homoploid hybridization between Pinus tabuliformis and Pinus yunnanensis (Wang and Szmidt 1990, 1994; Wang et al 2011). The distribution and altitudinal range of the three species forms a succession: P. densata is found at the highest altitude of all Pinus in Asia, while P. yunnanensis is found in a relatively limited range in southwestern China from 700 to 3000 m. Pinus tabuliformis is widely distributed from northern to central China at altitudes below 2700 m a.s.l.

Methods

Results

Conclusion