# Fine‐Scale Spatial Genetic Structure and Leaf Shape Variation in Five Fagaceae Species: Insights Into Conservation and Adaptation

## TL;DR

This study examines genetic and leaf shape variation in five oak and chestnut species to understand their adaptation and conservation needs.

## Contribution

The study reveals distinct fine-scale genetic structures and leaf shape differences between Quercus and Castanopsis species, offering insights for conservation.

## Key findings

- Quercus species show stronger fine-scale genetic structure and limited gene flow compared to Castanopsis species.
- Leaf shape variation is significant, with the greatest differences in leaf area and mass among the studied species.
- All species exhibit diminishing returns in leaf trait scaling, with C. fargesii showing the most pronounced effect.

## Abstract

Fine‐scale spatial genetic structure (fine‐scale SGS) refers to the pattern of spatial distribution of genetic variation at the local scale, which can indirectly estimate gene flow among individuals and reveal microevolutionary processes in plant populations. Although fine‐scale SGS is important in explaining dispersal patterns and adaptive variation in plants, few studies have explored its potential application in species conservation strategies. In addition, phenotypic traits, particularly leaf shape, may also exhibit specific spatial variation patterns at fine scales. In this study, we investigated the genetic and leaf shape variation of two genus Quercus species (
Quercus glauca
Thunb. and Q. multinervis J. Q. Li) and three genus Castanopsis species (Castanopsis tibetana Hance, C. faberi Hance, and
C. fargesii
Franch.) in Wuyishan National Park in southeastern China. Using genetic markers, we found that Quercus species exhibited stronger fine‐scale SGS and more limited gene flow than Castanopsis species, suggesting greater habitat fragmentation affecting local Quercus species. Leaf morphological analysis revealed inter‐generic differences and partial overlap in leaf shape between Quercus and Castanopsis species, with the greatest variation observed in leaf area (LA) and leaf mass (LM). In addition, all five Fagaceae species exhibited significant diminishing returns, with
C. fargesii
showing the most pronounced effect and possessing the smallest leaves, which may enhance its adaptability to the harsh environments. Despite the leaf shape overlaps blurring species boundaries between Quercus and Castanopsis species, their genetic structure is remained clearly distinct. The observed differences in the intensity of fine‐scale SGS and leaf shape variation between the two genera reflect their different environmental adaptability, offering new insights into the integration of genetic and phenotypic data for conservation planning.

We investigated both fine‐scale SGS and leaf shape variation in five Fagaceae species (
Q. glauca
, Q. multinervis,
C. tibetana
, C. faberi, and
C. fargesii
) from the genera Quercus and Castanopsis in Wuyishan National Park. We found that Quercus species exhibit stronger fine‐scale SGS than Castanopsis species. These two genera show differences in leaf shape, and all five species exhibit a pattern of diminishing returns in leaf trait scaling. Our findings underscore the importance of conserving fine‐scale SGS and considering leaf shape variation in the design of effective conservation strategies.