Certain plants, like Zanthoxylum above (Wikipedia Commons), have seeds dispersed by animals without the usual rewards of sugary fruit-pulp or oily arils. The real payment is vital although it seems intangible.
Prof. Mumblebard claims: “Plants attract seed-dispersing animals by offering packages of food-energy, such as sugary fruit-pulp or oily arils. Such packages fuel the transportation of the seeds. Plants that achieve dispersal by means of unrewarding, but conspicuous and appealing, packaging of the seeds do so simply by means of deception. Genera such as Zanthoxylum exploit the hardwired response of animals to conspicuous objects that mimic real, edible fruits.”
Robin and the Honey Badger respond: “Surprisingly many plants achieve seed-dispersal by attracting frugivores without providing any substantial reward for the animals to swallow and disperse the seed – whether by defecation or regurgitation – in a viable condition. Indeed, birds and mammals of such variety disperse the seeds of widespread genera such as Zanthoxylum that the attraction to their fruits could not be sustained were it based merely on false advertisement. There must be a more basic reason. A clue to the real reward is the medicinal value of plants to humans. The genus Zanthoxylum is, for example, renowned for various medicinal effects including analgesic, anti-oxidant, anti-microbial and anti-inflammatory. This genus is also well-known for its production of various alkaloids. One of these, sanguinarine, is used in commercial toothpastes and oral rinses because even trace amounts of it inhibit bacterial growth. Such strong and variable medicinal properties suggest that plants such as Zanthoxylum pay birds and mammals for dispersal by supplying a dispensary of medicinal formulations from within dry and indigestible fruit-walls, capsules, and seed-coats. Although the medicinal effects of these substances may be subtle, similar subtlety is acknowledged in plants which reward seed-dispersing animals with fruit-pulp that contains health-enhancing vitamins.”
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