Leandra

I'm sure I've noted before that there are a number of plant families that form significant components of the world's flora but tend to glide under the radar of popular representation owing to their largely tropical distributions. One of the prime examples is the Melastomataceae, an assemblage of over 5000 known species that represents one of the ten largest recognised plant families. Melastomes often stand out from other tropical plants by their distinctive leaves, which are opposite with acrodromous venation (several strong longitudinal veins arch outwards from the base to converge near the tip) and flowers that often bear large, colourful anthers (New York Botanical Garden). They are most diverse in the Neotropics with one of the significant genera found in this region being Leandra.

Leandra subseriata, copyright James Gaither.

As currently recognised, Leandra includes over two hundred species with the highest diversity centred in southeastern Brazil. Leandra forms part of the tribe Miconieae, distinguished by flowers with more or less inferior ovaries and fleshy berry fruits. Genera within the Miconieae have historically been difficult to define; as early as 1891, the Belgian botanist Alfred Cogniaux declared that they were essentially arbitrary. Leandra was supposed to be defined by its acute petals and terminal inflorescences but it has not always been clear whether a given species can be said to possess these features or not. It should therefore come as no surprise that the genus Leandra proved to be polyphyletic with the advent of molecular analysis (Martin et al. 2008). Nevertheless, a large clade centered on southern Brazil has continued to be referred to as Leandra sensu stricto.

There appear to be few if any direct observations of pollination in Leandra but flower morphology and comparison with related genera suggests that they are buzz-pollinated with pollinators taking pollen as a reward (Reginato & Michelangeli 2016b; buzz-pollination referring to pollination by bees where the bee's buzzing induces the flower to release pollen). Apomixis, with seeds being produced directly from ovule tissue without pollination, is not uncommon and may even be the majority condition (Reginato & Michelangeli 2016a). Seeds are dispersed by birds feeding on the berries. Many Leandra species appear very localised in distribution and they are particularly diverse in a number of high altitude areas. Species vary in their preferred habitat from disturbed to undisturbed; those species found in undisturbed locations are rare components of the understory, but those found in disturbed habitats may be among the most abundant shrubs in the area.

REFERENCES

Martin, C. V., D. P. Little, R. Goldenberg & F. A. Michelangeli. 2008. A phylogenetic evaluation of Leandra (Miconieae, Melastomataceae): a polyphyletic genus where the seeds tell the story, not the petals. Cladistics 24: 315–327.

Reginato, M., & F. A. Michelangeli. 2016. Diversity and constraints in the floral morphological evolution of Leandra s.str. (Melastomataceae). Annals of Botany 118: 445–458.

Reginato, M., & F. A. Michelangeli. 2016. Untangling the phylogeny of Leandra s.str. (Melastomataceae, Miconieae). Molecular Phylogenetics and Evolution 96: 17–32.