Genetic, geographic, and climatic factors jointly shape leaf morphology of an alpine oak, Quercus aquifolioides Rehder & E.H. Wilson

Abstract

Key message Leaf symmetry and leaf size are explained by genetic variation between and within lineages and to a lesser extent by climatic factors, while leaf asymmetry can only be partly explained by geographic factors in Quercus aquifolioides Rehder & E.H. Wilson.Context Leaves are the primary photosynthetic organs of plants, and their morphology affects various crucial physiological processes potentially linked to fitness. Aims We explored the variation in leaf morphology of an alpine oak, Quercus aquifolioides, in order to examine its relationship to genetic, geographic, and climatic factors. Methods We conducted a genetic survey using 25 nuclear microsatellites. Based on Bayesian clustering analysis, 273 sampled trees from 29 populations of Q. aquifolioides were assigned to two lineages that correspond to the Western Sichuan Plateau-Hengduan Mountains (WSP-HDM) and Tibet geographic areas, with some individuals showing mixed ancestry. To undertake morphological analyses, we collected 1435 leaves from these trees and characterized them in terms of 13 landmarks. The metric dimensions of these leaves were digitally captured in the two-dimensional coordinates of these landmarks, then divided into leaf size and symmetric and asymmetric components of leaf shape. To analyze how different components of leaf morphology vary across lineages, we employed Procrustes Analysis of Variance (ANOVA), two-block partial least-square analysis (2B-PLS), and several other multivariate analysis approaches. We also applied distance-based redundancy analysis (dbRDAs) to explore relations between leaf morphology and genetic, geographic, and climatic factors. Results Multivariate analysis indicated significant differentiation in leaf symmetric shape components and leaf size between the WSP-HDM and Tibet lineages, while the mixed individuals were morphologically intermediate. The dbRDA analysis showed that most of the variation in symmetric components and leaf size was explained by genotypic effects, with the symmetric components of leaf shape being also significantly explained by geography and climate; however, variation in asymmetric components is only very weakly explained by geography. Conclusion Our results demonstrated that leaf morphological variation in shape and size across Q. aquifolioides geographic range is related to both its genetic differentiation and to a lesser extent to climatic factors. We discuss how these patterns could be interpreted in terms of both geographical isolations among and within lineages, and possible adaptive responses for particular traits, in contrast to asymmetric variation.

Population and Landscape Genetics Provide Insights Into Species Conservation of Two Evergreen Oaks in Qinghai–Tibet Plateau and Adjacent Regions

“…The allele sizes were subsequently scored using GeneMarker v. 2.2 (Softgenetics, United States), and the genotypes were checked visually two times. A subset of the data, 959 individuals from 58 study sites of Q. aquifolioides at 15 nSSRs, were from Du et al (2017) and Li Y. et al (2021) , and the additional data were first reported in this study.…”

Patterns of leaf morphological variation in Quercus frainetto Ten. growing on different soil types in Serbia

“…To minimize the risk of clone selection, the populations were at least 10 km apart and all sampled individuals were located at least 5 m from each other [33]. From each individual, 10 fully developed leaves were collected at a height of 8-10 m around the crown of each tree [34], mainly under shaded conditions.…”

Asymmetric character displacement in mixed oak stands

“…The possible adaptive response of this variation to environmental conditions has been extensively investigated, perhaps more so than in any other plant genus (e.g. Zwieniecki et al ., 2004; Niinemets, 2015; Hipp et al ., 2018; Cavender‐Bares, 2019; Royer et al ., 2019; Li et al ., 2021; Sancho‐Knapik et al ., 2021; Skelton et al ., 2021). The oak genus is also a classic example for hybridization and introgression studies (Darwin, 1872; Rieseberg et al ., 2006).…”