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Why are slime molds no longer classified in kingdom Fungi?

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Two Amanita pantherina mushrooms with brown caps covered in white spots grow among moss and fallen leaves. — fungus A pair of panther cap mushrooms (*Amanita pantherina*). Closely related to the death cap mushroom (*Amanita phalloides*), the panther cap is highly poisonous.

Slime molds were historically grouped with fungi due to superficial resemblances, such as the production of spore-bearing structures. However, they are no longer classified as true fungi because they are fundamentally different organisms.

The primary distinction lies in their mode of nutrition and cellular characteristics. While fungi obtain nutrients by excreting digestive enzymes and absorbing them externally, slime molds exhibit behaviors more similar to protozoan protists, such as engulfing food. Furthermore, modern molecular phylogenetic analysis has clarified that kingdom Fungi is a monophyletic group—meaning all true fungi share a single common ancestor—and slime molds do not fit within this lineage. Their exact evolutionary relationship to other organisms remains unclear, and they are now excluded from the kingdom Fungi entirely.12