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bioRxiv · 10.64898/2026.07.22.740078

A continuum of CAM phenotypes in the carnivorous plant genus Pinguicula (Lentibulariaceae)

Mok, D. W. L.·VanBuren, R.·Gilbert, K. J.
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Abstract

PremisePinguicula are carnivorous plants occupying a wide range of habitats, from wetlands to barren rock cliffs, where CAM photosynthesis was recently discovered in several species. This ecological and physiological diversity makes the genus a promising system for exploring the environmental drivers and evolutionary transitions underlying variation in CAM. Here, we present a physiological survey of CAM with a particular focus on the Mexican Clade, which contains the recently identified CAM species. MethodsWe conducted a carbon isotope survey of live and herbarium specimens to identify candidate CAM species. We then measured diurnal gas-exchange patterns and changes in leaf titratable acidity to quantify CAM activity. ResultsPinguicula species exhibited a variety of photosynthetic phenotypes. Pinguicula vulgaris showed no detectable evidence of CAM, whereas P. cyclosecta and P. moranensis demonstrated a C3-CAM physiology with most net assimilation via C3. Pinguicula martinezii also showed the same C3-CAM physiology under well-watered conditions but had strong facultative induction of CAM with drought. Pinguicula agnata displayed net assimilation via CAM. Titratable acidity had a positive correlation with {delta}13C within the species we sampled. ConclusionsOur results support the existence of a CAM physiological continuum within Pinguicula. Notably, closely related species encompass physiologies that span the large variation of CAM. This diversity provides a rare opportunity for future studies to investigate the evolution of CAM in closely related species, including differences and similarities between differing states across the continuum.

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Mok, D. W. L., VanBuren, R., Gilbert, K. J.. 2026-07-23. A continuum of CAM phenotypes in the carnivorous plant genus Pinguicula (Lentibulariaceae). https://doi.org/10.64898/2026.07.22.740078

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