Abstract
Fruit traits affect population genetic diversity by affecting seed protection and dispersal strategies, thereby comprising important components of phenotypic variation. Understanding of the phenotypic variation is an indispensable first step for developing breeding strategies. However, little information is known about the genetic variation in E. japonica—a monotypic species with abundant phenotypes that is mainly distributed in southern China. In this study, we evaluated the phenotypic diversity of 67 E. japonica using 23 phenotypic traits. Our results showed that the Shannon–Wiener (I) index of qualitative traits ranged from 0.55 to 1.26, and the color traits had a relatively high I. The average coefficient of variation of compound leaf traits (14.74%) was higher than that of fruit and seed traits (12.77% and 11.47%, respectively). Principal component analysis also showed that compound leaf and fruit traits were important components of total variation. Furthermore, correlation analysis revealed a significant difference in elevation and fruit color, irregular ribs, leaf margin and texture. The F value within populations was smaller than among populations, indicating the variation in phenotypic traits among populations was much greater than within populations. Dehua and Zunyi populations had the highest coefficients of variation, whereas Wenzhou population had the smallest—which may be attributed to habitat destruction. According to Q-type clustering, 67 samples clustered into four groups, with those having similar phenotypes clustering into the same group. In general, leaf and fruit traits had abundant phenotypic diversity, representing the main sources of phenotypic variation. Combined with clustering results and field surveys, this study suggests that the phenotypes of E. japonica are classified into two main categories: The deciduous E. japonica present at high altitudes; and the evergreen E. japonica present at low altitudes. Excavating E. japonica variations provides a theoretical reference for its classification and diversity, and is of great significance for planning genetic resources and establishing conservation strategies.
Highlights
Tree evolution is largely driven by adapting previous seed protection and dispersal strategies that allow diversification into new niches [1]
Zunyi and Wenzhou populations were defined as large-leaf E. japonica, and Dehua as small-leaf E. japonica
Field investigation showed that the higher the altitude, the redder the fruit color; and the reddish fruit color, the reddish color of fruit sequence, the color of annual branch and the color of compound petiole. we found that E. japonica with red fruit, epidermis ribs prominent, leafy papery or thick papery, margin serrulate were present in high-altitude areas (300m~1000m), while E. japonica with fruit epidermis rib inconspicuous, leaf membranous, and margin obtuse serrate were present in lowaltitude areas (100m~500m)
Summary
Tree evolution is largely driven by adapting previous seed protection and dispersal strategies that allow diversification into new niches [1]. Variations in fruit traits are very important aspects of a population’s survival and genetic diversity during evolution. A fundamental source of biodiversity, provides the raw material for evolution by natural selection [4], which includes phenotype, protein, and DNA variations. Using variation traits to study phenotypic diversity, revealing the genetic structure and variation size of the population form the basis of genetic breeding. Phenotypic variance is thought to be the result of natural selection, reflecting both adaption to local environmental characteristics and genetic diversity [7,8,9], such as meteorological change, trait mutation, and genetic drift [10]. Plant phenotypes result from interactions between genotype and environment, reflecting genotype adaptation to environmental changes. Phenotypes reflect plants’ environmental adaptability, and phenotypic variation is of great significance in adaptation and classification
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