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How did the APG IV classification system change the boundaries of Lamiales?

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Water mint (Mentha aquatica) — Lamiales The lilac-pink flowers of the water mint attract butterflies and beetles.

The APG IV classification system significantly expanded the boundaries of the order Lamiales compared to older, morphology-based systems like the one proposed by Arthur Cronquist.12

Under the APG IV system, the order is much more heterogeneous than it was previously. This expansion was driven by molecular techniques—specifically the sequencing of DNA from chloroplasts and nuclei—which provided more robust data on plant phylogeny than traditional morphological, chemical, and anatomical characters.21

As a result of these molecular analyses, the circumscription of Lamiales was adjusted to include a broader range of families that share common technical and molecular characteristics, such as the production of unique chemical compounds (e.g., oxygenated flavones), specialized stomata, and the storage of carbohydrates as oligosaccharides rather than starch. The current APG IV classification of Lamiales encompasses 24 families, including major groups such as Lamiaceae, Plantaginaceae, Scrophulariaceae, and Acanthaceae, among others.231