Morpho-anatomy and habitat characteristics of Xanthostemon verdugonianus Náves ex Fern.-Vill. (Myrtaceae), a threatened and endemic species in the Philippines

Abstract

A study provided insights on morphoanatomy of Xanthostemon verdugonianus, an endemic and vulnerable species in the Philippines. Sampling was conducted in its natural habitat with presence of dominant vegetation and rehabilitated sites of the species. In a purposive manner, quadrats were established to collect samples and describe the morpho-anatomy, associated species, and soil particle characteristics. The leaf is opposite with a distinct reddish color when young in shoot terminal. The leaf cuticle is distinctly thick, hypostomatic with presence of paracytic stomata, and the compact spongy layer could be an adaptation to xeric conditions. The stem and roots contain tissues manifesting secondary growth having secondary xylem and formation of outer bark. Inflorescence is corymb, complete flower is bright red, with prominent cup-shaped hypanthium, persistent lobe-shaped calyx, and inferior ovary. Fruit is globular capsule round-ovoid in shape with a woody texture. Placental seeds are visible upon splitting of matured fruits which are flattened and deltoid to semicircular shape. A total of 31 species under 18 flora families are associated with X. verdugonianus with the mean abundance of 8 species per plot. Ultramafic substrate was dominantly composed of medium sand particles, and the reddish color indicating oxidation of metallic elements in the soil. Analyzing the morpho-anatomical features can help to explain its endemicity, survival in the wild, and adaptation to climate change.