40 million years of friendship between Yucca plants and their moths Yucca plants (genus Yucca) and Yucca moths (family Proxidae) they are the classic example of desert-dwelling species that rely on obligate mutualism to support each other. Using mitochondrial DNA to make a phylogenetic reconstruction of evolutionary history, they were able to demonstrate that this unique relationship developed over about 40 million years. This has led to a very complex relationship between the numerous species of Yuccasella and Proxidae. (Pellmyr, 9178) While there are about 49 species of plants in the United States alone, each plant can have one or more specialized pollinator moths and even some parasitic species (cheaters) lead to about 98 species and subspecies of moths. Yucca is a plant widespread throughout the United States; however the greatest diversity lies in the southwestern desert region with approximately 19 species. This has led scientists to believe that mutualism evolved somewhere in the Southwest. (Pellmyr, 9178) All plants and their pollinating moths have a finely evolved pollination and reproduction system that works together to ensure the continuation of each other's species. Female moths have developed specialized prehensile tentacles that evaginate from the maxillary palps. (Powell, 12) This allows the moths to intentionally collect pollen from one flower, then move to another where it lays its eggs (depending on the individual species) in the locular cavity or in the shallow cavities of the perianth. (Althoff, et al 399) After oviposition the female deposits pollen on the stigma, thus beginning the pollination cycle of the yucca plant. Male moths also have not developed... middle of paper... moths also parasitize the plant, but do so at a much later stage of pollination, actually damaging the plant in the process, destroying up to 85% of it of the seeds. (Pellmyr, 155) This species has actually developed a knife-like appendage to oviposit eggs deep inside the hard fruit on the seeds avoiding the defensive mechanism developed by the yucca. One of these mechanisms is flower abscission. Each time a moth lays eggs in the ovule it damages the flower a little. With pollinating moths it is never enough to cause permanent damage, this is largely why they only oviposit on one flower and move on to the next. Trickster species lay eggs many times the amount they should, causing significantly more damage to surrounding eggs. This causes the plant to abscise the flower and ultimately abort both the flower and moth eggs. (Althoff, 302)