Host specialization by reproductive interference between closely related herbivorous insects

Abstract

Host specialization among closely related herbivores is common and is therefore a major theme in ecology. Despite its ecological importance, no general explanatory framework for host specialization is currently available. We introduce a new model of the evolution of host specialization in herbivorous insects. We use a twodimensional lattice comprising 32 9 32 cells. Moreover, the model incorporates reproductive interference, defined as any negative outcomes resulting from interspecific mating, between two species of herbivores feeding on two different host plants as well as ordinary resource competition and differences in host suitability. Our simulation showed that reproductive interference, together with other factors such as host-related performance and resource competition, can actually drive the evolution of host specialization and thereby host partitioning between herbivorous insects during secondary contact. Host specialization arises particularly when levels of both reproductive interference and resource competition are intermediate. In contrast, host specialization seldom occurs if reproductive interference is absent. Thus, reproductive interference is as key to specialization as is spatial partitioning, which was not regarded as a realistic outcome when only resource competition was considered.

Reproductive interference: ecological and evolutionary consequences of interspecific promiscuity

“…If a trait involved in mate recognition also affects resource use, reproductive interference may result in apparent ecological character displacement (Konuma and Chiba 2007). In other cases, habitat partitioning or host specialization may evolve to prevent interspecific encounters (e.g., Colwell 1986;Nishida et al 2015;Noriyuki 2015). Potential consequences of reproductive interference, including ones not mentioned in the text, are listed in Table 1.…”

“…Thus, male interspecific promiscuity can be maintained even at evolutionary equilibria. Nishida et al (2015) explore how male interspecific promiscuity affects species distributions by using individual-based models that simulate secondary contact between two herbivorous insects. They show that whether interacting species display sympatry, parapatry, or host specialization depends on the strength of the reproductive interference as well as on factors such as resource competition and fecundity.…”

Host selection in insects: reproductive interference shapes behavior of ovipositing females

“…If the performance of the focal species is lower than that of the interfering species on all hosts, then the population of focal species is unlikely to persist stably in the regional environment (Crowder et al 2011;Nishida et al 2015). In particular, when reproductive interference is intense, stable regional coexistence of the two species requires there to be a large performance difference between them (Crowder et al 2011;Nishida et al 2015).…”

“…The performance of a species on a particular host, that is, its survival and the successful development of the offspring, can be affected by multiple factors, including predation pressure from natural enemies (e.g., Nosil and Crespi 2006) and the nutritional quality of the food sources (e.g., Via 1991). If the performance of the focal species is lower than that of the interfering species on all hosts, then the population of focal species is unlikely to persist stably in the regional environment (Crowder et al 2011;Nishida et al 2015). In particular, when reproductive interference is intense, stable regional coexistence of the two species requires there to be a large performance difference between them (Crowder et al 2011;Nishida et al 2015).…”

“…Therefore, the model of Konuma and Chiba (2007) may provide a theoretical basis for the evolutionary differentiation as well as the ecological maintenance of host selection among species when reproductive interference occurs. Nishida et al (2015) constructed an individual-based model with a gridded spatial structure in which each grid cell can contain two herbivore species but only one of two host plant species. This model assumes that the two herbivore species might engage in both reproductive interference and resource competition if both species utilize the same patch.…”