Host‐plant associated genetic divergence of two Diatraea spp. (Lepidoptera: Crambidae) stemborers on novel crop plants

Abstract

Diatraea lineolata and Diatraea saccharalis (Lepidoptera: Crambidae) are moths with stemboring larvae that feed and develop on economically important grasses. This study investigated whether these moths have diverged from a native host plant, corn, onto introduced crop plants including sorghum, sugarcane, and rice. Diatraea larvae were collected from these four host plants throughout the year in El Salvador and were reared on artificial diet until moths or parasitoids emerged. Adult moths were subsequently identified to species. Amplified fragment length polymorphisms (AFLPs) and mitochondrial DNA cytochrome oxidase I (COI) were used to examine whether or not there was genetic divergence of D. lineolata or D. saccharalis populations on the four host plants. Percent parasitism was also determined for each moth on its host plants. D. lineolata was collected from corn in the rainy season and sorghum in the dry season. D. saccharalis was most abundant on sugarcane in the rainy season and sorghum in the dry season. The AFLP analysis found two genetically divergent populations of both D. lineolata and D. saccharalis. Both moths had high levels of parasitism on their dominant host plant in the rainy season, yet had low levels of parasitism on sorghum in the dry season. The presence of two genotypes of both Diatraea spp. on sorghum suggest that host‐associated differentiation is occurring on this novel introduced crop plant.

Influence of host plant, geography and pheromone strain on genomic differentiation in sympatric populations of Ostrinia nubilalis

“…In many diverging populations of Lepidoptera, ecological factors such as host plant use co‐vary with differences in sexual signals (Groot et al, ; Joyce et al, ), but in few cases has the relative contribution of these factors to genetic structure been tested (Gouin et al, ; Prowell, McMichael, & Silvain, ). Ostrinia nubilalis is an emerging model for speciation dynamics due to sympatric ecotypes or strains that vary in voltinism and sex‐pheromone communication (Coates et al, ; Dopman et al, ; Kozak et al, ; Lassance, ; Olsson et al, ).…”

Host plant or geographic barrier? Reproductive compatibility among Diatraea saccharalis populations from different host plant species and locations in Argentina

“…This is in the case of the northwestern and Pampas populations of D. saccharalis (Fogliata et al., ), suggesting they may be incipient species (Nosil, ). Other studies, using biological, morphological, and physiological traits (Box, , ; Pashley et al., ; Cortés et al., ) or molecular tools, showed the existence of distinct lineages among populations of SCB from other regions (Lange et al., ; Cortés et al., ; Joyce et al., , ; Pavinato et al., ). Genetic divergence studies of SCB, using amplified fragment length polymorphism (AFLP), simple sequence repeats polymorphisms (SSR), and cytochrome oxidase subunit 1 (COI), suggest a marked host‐plant‐associated differentiation among populations from sugarcane, rice, maize, and sorghum (Joyce et al., ; Pavinato et al., ).…”

“…Currently, D. saccharalis is the most widely distributed species within the genus Crambidae. It is distributed from the southern region of the USA (30°N) to South America (30°S) excluding the country of Chile (Dyar & Heinrich, ; Box, , , ; Joyce et al., ).…”

“…Thus, the reduced gene flow between insect populations could lead to reproductive isolation (Groot et al., ), affecting the sustainability of the Bt crop over time. This has led to increased interest in genetic structure and gene flow within and among SCB populations and the possible exchange of alleles between geographically distant and host‐plant‐adapted populations (Joyce et al., , ).…”

“…These studies show evidence of the existence of barriers to gene flow, as a result of host plant associations. This could lead to reproductive isolation among populations from different host plants driven by phenological, phytochemical, and/or morphological differences (Bush, ; Diehl & Bush, , ), generating a process of speciation and divergence among these populations (Joyce et al., ; Pavinato et al., ).…”