"I get by with a little help from my friends."
Yuccas are plants which define the Mojave Desert. The Joshua Tree (Yucca brevifolia),pictured below, is probably the most famous example of a Yucca, which are surprisingly close relatives of some Orchids and Asparagus.
The Joshua Tree, Yucca brevifolia
Yuccas rely on moths for a very interesting sort of mutualism. Unlike other pollinators where pollen often gets stuck to the body of the insect, the Yucca Moths seem to be more deliberate about the act. Actually scraping pollen off Yucca Flower anthers and delivering it to another Yucca. The benefit to the moth being that they lay their eggs in the flower of the Yucca. The moths do not eat the pollen from the Yucca Flower. So by the act of purposely pollinating the Yucca flowers do not actually see any immediate benefit. It will be years before the pollination event spawns another mature Yucca and by that time it will be her great, great, great, grandchildren moths who are reaping the benefits. Talk about foresight!
One thing that puzzles scientists about mutualisms like this is their apparent instability. One could guess that evolution might favor moths that "cheat" and lay their eggs in the Yuccas but do not pollinate, which is labor intensive and potentially costly. Likewise how can a Yucca ensure that it is not providing shelter for the offspring of moths that didn't carry its pollen elsewhere?
In fact cheaters have evolved and entered this system. There are many species of moth which lay their eggs in the flowers or seeds of Yuccas but are not pollinators. Yuccas are able to respond and prevent this type of exploitation of their flowers and seeds by aborting ones which house large numbers of moth eggs.
Cheater moths do rely on the presence of the mutualist species because they rely on the persistence of the Yucca. If the mutualism between the Yucca and symbiotic moths were to break down and Yucca were to fail to persist than the cheater species would likely go extinct, or would need to enter into the mutualism itself.
This interaction is incredibly complex and the behavior of the moth mutualists and cheaters is variable but well studied. If this subject interests you I suggest you take a look at some of the sources below. The system has advanced theoretical work on the evolution of mutualisms and knowledge of how mutualistic interactions evolve and under what circumstances they break down.
References and further readings:
Pellmyr, Olle, and James Leebens‐Mack. "Reversal of mutualism as a mechanism for adaptive radiation in yucca moths." the american naturalist156.S4 (2000): S62-S76.
Ferriere, Régis, et al. "Cheating and the evolutionary stability of mutualisms."Proceedings of the Royal Society of London. Series B: Biological Sciences269.1493 (2002): 773-780.
Segraves, Kari A., David M. Althoff, and Olle Pellmyr. "Limiting cheaters in mutualism: evidence from hybridization between mutualist and cheater yucca moths." Proceedings of the Royal Society of London B: Biological Sciences272.1577 (2005): 2195-2201.
Addicott, John F., and Andrew J. Tyre. "Cheating in an obligate mutualism: how often do yucca moths benefit yuccas?." Oikos (1995): 382-394.