Spatially explicit information on morphological variation within natural Haloxylon ammodendron populations remains limited. We examined size-associated morphological and spatial variation in a natural population on the eastern margin of the Badain Jaran Desert. Plant height, crown diameter, and stem-base diameter were measured for 1,151 individuals. Based on the lower and upper quartiles of stem-base diameter, individuals were classified into small, intermediate, and large stem-base diameter classes. Descriptive statistics and geostatistical analyses were used to characterize morphological variation and model spatial dependence. Mean plant height and crown diameter increased across the small, intermediate, and large stem-base diameter classes. The interpolated maps showed spatial variation in all measured traits. Plant height and crown diameter exhibited partially similar spatial patterns, whereas stem-base diameter showed a different spatial pattern. The fitted semivariogram parameters also differed among traits and diameter classes. The observed differences represent size-associated morphological and spatial variation rather than independently validated age-dependent changes. Because soil moisture, groundwater depth, local topography, wind fields, and plant interactions were not directly measured, the environmental mechanisms underlying the observed patterns remain unresolved.
Abstract Polyploidy is a major driver of plant evolution and speciation. Autopolyploidy, in particular, plays a key role in the emergence of cryptic lineages that are morphologically similar yet genetically and ecologically distinct. We investigated the extent of genetic exchange and climatic differentiation between diploid (2×) and hexaploid (6×) cytotypes of Aster amellus (Asteraceae) within a narrow contact zone in Central Europe to assess whether reproductive isolation and divergence are maintained where cytotypes occur in close proximity. We implemented a spatially explicit sampling of 735 individuals from 32 adjacent diploid and hexaploid populations located 1–10 km apart. Genetic variation was analysed using nuclear microsatellite markers, and ecological divergence was quantified through hypervolume‐based niche analysis. We found strong genetic differentiation between cytotypes, with hexaploids exhibiting higher genetic diversity and occupying a broader climatic space than diploids. Genetic connectivity was high within cytotypes, but sharply reduced between them, and evidence of a recent polyploidization event in one population revealed hexaploid individuals genetically close to the diploid cluster, suggesting recurrent formation of hexaploids. Our findings indicate that reproductive isolation between cytotypes remains effective even at fine spatial scales, maintaining both genetic and ecological divergence despite geographical proximity. Fine‐scale sampling reveals that narrow diploid–polyploid contact zones increase the likelihood of detecting early‐stage polyploid formation before such signals are obscured by drift or selection, reinforcing their role as key natural laboratories for studying cryptic autopolyploid speciation.
Abstract Climate change has been linked to the intensification of forest pest outbreaks, posing a serious threat to non‐coevolved tree species because of their potentially weak defensive capabilities. However, unlike broad‐scale climatic disturbances such as drought and heatwaves, insect outbreaks are highly heterogeneous in space and among host species, and the response of occurring conifers to such outbreaks remains poorly understood. The core area of the Changbai Mountain Nature Reserve in northeastern China was severely defoliated in 2019 by larch caterpillars ( Dendrolimus superans Butler)—a conifer‐feeding defoliator that prefers larch but also attacks other conifers. In this region, a vegetation transition zone between the broadleaf‐Korean pine and spruce–fir forests hosts multiple conifer species co‐existing within short distances under similar defoliation intensities. We monitored 1,837 trees in 2019 (pre‐disturbance), 2021 and 2024, and sampled needles of healthy individuals of each species in 2024 to obtain species‐level proxies of intrinsic foliar traits. Results revealed that: (i) mortality of attacked Korean pine peaked within 2 years, with little subsequent increase, resulting in a cumulative mortality rate of 31.3%; in contrast, mortality of spruce and fir continued to increase until the fifth year, reaching a combined cumulative rate of 78.6%, while larch exhibited nearly 100% survival. (ii) a deciduous habit, low needle biomass allocation and low carbohydrate concentrations enhanced survival by reducing canopy regeneration costs. (iii) regarding radial growth responses, spruce showed stronger compensatory growth but weaker recovery ability than fir and Korean pine, likely due to its limited carbon and nutrient reserves. Considering these findings, prioritizing the protection of non‐coevolved conifers is recommended to minimize biomass loss during pest outbreaks. This study also provides important insights for temperate and boreal conifer forest conservation, highlighting the high vulnerability of spruce–fir forests to larch caterpillar outbreaks.
