Host-dependent Life Cycle Variations in Papaya Mealybug Paracoccus marginatus and Their Implications for Divergent Natural Selection

Background: This study was undertaken to understand how host plant variations influence the life cycle and adaptability of Paracoccus marginatus. It aims to reveal how such host-dependent differences drive divergent natural selection and pest evolution. Methods: Paracoccus marginatus life cycle on different host plants was investigated utilizing both stage-specific (vertical) and age-specific (horizontal) life tables. These studies revealed significant biological variation in PMB performance across different hosts. Result: Among the tested host plants viz. papaya, cotton, tapioca mulberry, brinjal and hibiscus, papaya supported the highest net reproductive rate, reaching 559.48 females per female, whereas the lowest was recorded in tapioca at 282.53. The capacity for population growth (rc) also varied, being highest in papaya (0.512) and lowest in tapioca (0.324). Correspondingly, the intrinsic rate of increase (rm), which reflects the potential for population expansion per day, peaked in papaya at 0.570 and dropped to 0.342 in tapioca. Analysis of cumulative K values, representing total generation mortality, showed lower values in females than in males across all hosts. In papaya, the K value was the lowest for both sexes 0.0325 in females and 0.0587 in males indicating lower mortality. Conversely, tapioca showed the highest K values, with 0.1405 in females and 0.1799 in males. These results demonstrate how host plants have a major impact on papaya mealybug population dynamics and survival rates.