Final answer:
The studies on the mutualism between yuccas and yucca moths by Pellmyr and Huth showed that yucca plants impose penalties on moths that lay too many eggs. This penalizing mechanism ensures a balanced mutualistic relationship between the plant and the pollinating moths.
Step-by-step explanation:
The studies by Pellmyr and Huth regarding the mutualistic relationship between yuccas and yucca moths have provided insights into how this cooperation between species functions. Their research revealed a fascinating system of checks and balances within this mutualism. The yucca plants offer not only food in the form of nectar but also serve as a shelter for the yucca moth's larvae. In return, the yucca moths pollinate the yucca plants, which is crucial for the plant's reproduction. However, to ensure that the moths do not exploit the relationship by laying too many eggs, which would damage too many of the plant's seeds, the yucca plant has evolved a penalizing mechanism. When a yucca moth lays an excessive number of eggs, the yucca plant can selectively abort the flowers that contain too many moth larvae, thereby imposing a penalty on the moths for overexploitation.
This dynamic illustrates a sophisticated form of coevolution where both species benefit but also actively manage their interaction to avoid conflicts that might arise from the differing interests of the plant and the insect. As such, the correct answer is that yucca plants impose penalties on moths that lay too many eggs (Option 3), which helps to maintain the delicate balance of mutual benefit in this symbiotic relationship.