Morphological and Molecular Evidence for a New Species of Ilex (Aquifoliaceae) from Guangdong, China, with Insights into Its Phylogenetic Position Within Ilex sect. Ilex

Ilex lanceifolia K.W.Xu & Lei Jiang, a new species from the western Pearl River Delta of Guangdong, China, is described based on morphological and molecular evidence. To test whether this newly discovered population represents a distinct lineage and to assess the congruence between leaf morphology and phylogeny, we integrated multivariate morphometrics, scanning electron microscopy, and phylogenetic analyses of nuclear ITS, ETS, and nepGS sequences. The new species resembles I. xiaojinensis and I. peiradena in shrubby habit and lanceolate leaves but differs by its prominently raised abaxial leaf veins forming distinct reticulate areoles, and green to purplish-black petioles and young branchlets. However, phylogenetic analyses unexpectedly place it within Ilex sect. Ilex forming a clade with I. graciliflora and six other species, rather than with its morphological look-alikes. This discordance strongly suggests that the lanceolate leaf shape has evolved convergently in multiple lineages of Ilex, likely as an adaptive strategy to the high-humidity, low-light understory conditions of subtropical lowland forests. The new species is currently known only from a single population in Jiangmen City, with several thousand individuals but an extremely restricted range (<20 km2), warranting conservation attention. This discovery highlights the underestimated biodiversity of lowland forests in the Pearl River Delta and underscores the need to prioritize remnant habitat fragments in rapidly urbanizing regions.