Reproductive Interference Among Coccinellids In The Genus Coccinella: Implications For The Impact Of Non-Indigenous Species
Reproductive interference is a powerful force that shapes ecosystems, influences species' distributions, and can contribute to the success of invasive species. I examined the role of hybridization and satyrization, two forms of reproductive interference, in the interactions between two North American native and one introduced species of lady beetle (Coleoptera: Coccinellidae). Through controlled pairings, I determined that hybridization between the introduced species, Coccinella septempunctata (C7), and two congeneric native species, C. novemnotata (C9) and C. transversoguttata (CT), is not possible and cannot be contributing to the decline of the native species. However, I quantified a significant fitness cost to C9 females for mating with a C7 male and a significant reduction in the propensity of both male and female C9 to mate with a conspecific after non-sexual encounters with C7. Additionally, I used the evolutionary relationships of each species pair, allopatric (C7/C9) or sympatric (C7/CT and C9/CT) to test the hypothesis that closely related allopatric species are more likely to intermate than sympatric congeners due to lack of recent interactions to reinforce isolating barriers. Not only were C7/C9 pairs more likely to mate than the sympatric pairs, but C7 was involved in a significant proportion of all heterospecific copulations. C7 may, therefore, impose a greater cost to C9, its allopatric congener than CT through reproductive interference. I conclude that hybridization can not be influencing the decline of these two native species, but satyrization of C9 by C7 does impose a cost to the native, but the extent of which it occurs in nature remains unknown. That C9, but not C7, was less likely to mate with a conspecific after repeated nonsexual encounters with a heterospecific raises interesting questions about the role of this behavior in the decline of C9 and may represent a cost to the evolution of satyrization-resistance. This has important implications for other declining native species. As the native becomes rarer and the invasive more common, the native will encounter heterospecifics more often than conspecifics. If this results in a decreased propensity to mate with a conspecific, already diminished populations may have little chance of recovery.
Lady beetle conservation; Reproductive interference; Coccinellid
Thaler,Jennifer S.; DiTommaso,Antonio
Ph. D., Entomology
Doctor of Philosophy
dissertation or thesis