The fragile ancient ‘Shuikoulin’ forests, which provide critical habitats for the critically endangered Blue-crowned Laughingthrush, are increasingly degraded by soil contamination and heavy metal pollution. This study examines the rhizosphere environment of four key ancient tree species in the bird’s core habitat, focusing on soil properties, heavy metal accumulation, and the structure of arbuscular mycorrhizal (AM) fungal communities. The results revealed that Liquidambar formosana showed the highest total nitrogen (TN) and available phosphorus (AP), whereas Quercus chenii had the lowest soil organic matter (SOM). The primary heavy metal contaminant across all tree species was Cd (Igeo > 2), followed by the metalloid As. We detected 41 AM fungal species spanning 7 genera, with Glomus dominating (84.19% relative abundance). OTU richness was highest in Cinnamomum camphora and L. formosana (110 each), followed by Q. chenii (88) and Castanopsis sclerophylla (75). Structural equation modeling indicated that soil nutrients (TN, TP, AP, SOM) suppressed the accumulation of V, Cr, Ni, and Cu, thereby indirectly favoring Glomus and Paraglomus. In contrast, higher pH and total potassium (TK) levels promoted Co and Zn bioavailability and negatively affected Acaulospora and other minor genera. Tree species identity directly modulated these interactions. Our findings demonstrate that ancient tree species shape AM fungal assembly through distinct rhizosphere geochemical niches, providing a mechanistic basis for restoring degraded habitats critical to endangered species conservation.

Supernumerary (B) chromosomes are widespread in numerous plants, including the Lilium genus. However, their origin remains unclear. This study used traditional and modern cytogenetics to analyze the triploid lily cultivar ‘Eyeliner’ (LAA) to identify the microsporogenesis, fertility, and chromosome composition of its progeny and record a case of potential B chromosome formation. The results indicated anomalous meiosis of LAA in all processes. In microspores, different cells had different numbers of chromosomes and fragments. Moreover, the fluorescence in situ hybridization (FISH) results showed that some fragments contained telomere signals at both ends. The LAA × AA progenies were aneuploid, with one progeny containing a small aberrant chromosome (potential B chromosome). The genomic in situ hybridization (GISH) results showed that the aberrant chromosome originated from the L genome. In contrast, the FISH results showed that the aberrant chromosome contained two telomere signals. This suggests that the anomalous meiosis of the triploid lily forms chromosome bridges, fragments, and small aberrant chromosomes (isochromosome), which eventually form aneuploid gametes containing small aberrant chromosomes passed on to the progeny. This study provides a case in which the potential B chromosomes are derived from the A chromosomes.