Comparative leaf anatomy and micromorphology of the Chilean Myrtaceae: Taxonomic and ecological implications

• We compared the leaf anatomy of all species of Chilean Myrtaceae for the first time.
• Leaf anatomy and micromorphology are useful for identifying species and genera.
• Xerophytic characters documented include hypodermis, trichomes and straight epidermal walls.
• Ontogenetic observations were conducted for secretory cavities and epidermis.
• Midribs of Blepharocalyx cruckshanksii and Nothomyrcia fernandeziana resemble their phylogenetic relationships.

The family Myrtaceae in Chile comprises 26 species in 10 genera. The species occur in a diverse range of environments including humid temperate forests, swamps, riparian habitats and coastal xeromorphic shrublands. Most of these species are either endemic to Chile or endemic to the humid temperate forests of Chile and Argentina. Although many taxa have very restricted distributions and are of conservation concern, little is known about their biology and vegetative anatomy. In this investigation, we describe and compare the leaf anatomy and micromorphology of all Chilean Myrtaceae using standard protocols for light and scanning electron microscopy. Leaf characters described here are related to epidermis, cuticle, papillae, stomata, hairs, mesophyll, crystals, secretory cavities and vascular system. Nearly all the species have a typical mesophytic leaf anatomy, but some species possess xerophytic characters such as double epidermis, hypodermis, pubescent leaves, thick adaxial epidermis and straight epidermal anticlinal walls, which correlate with the ecological distribution of the species. This is the first report on leaf anatomy and micromorphology in most of these species. We identified several leaf characters with potential taxonomic and ecological significance. Some combinations of leaf characters can reliably delimitate genera, while others are unique to some species. An identification key using micromorphological and anatomical characters is provided to distinguish genera and species.