Krameria tomentosa oil flowers and their pollinators: Bees specialized on trichome elaiophores exploit its epithelial oil glands

Oil flowers are spread over eleven angiosperm families and exploited by bees specialized on oil gathering. This reward is produced by glandular surfaces of specific floral whorls called elaiophores. Unlike trichome elaiophores, such as those of Plantaginaceae, Krameria species bear lateral petals modified into epithelial elaiophore, convergently similar to oil-secreting Malpighiaceae calyx. Krameriaceae is an oil-offering monotypic group of...