Reproductive isolation between two populations ofDiatraea saccharalis(F.) (Lepidoptera: Crambidae) from different host plant species and regions in Argentina

Abstract

The sugarcane borer, Diatraea saccharalis (F.), has a widespread distribution throughout the Western Hemisphere and is a pest of many crop plants including sugarcane, corn, sorghum and rice. The use of Bacillus thuringiensis (Bt) corn has been the primary tool for managing this species in corn fields. Sugarcane borer control has been recently threatened by observations of susceptibility and/or resistance to certain varieties of Bt corn and the protein used in many newer varieties. This has led to increased interest in understanding sugarcane borer genetic diversity and gene flow within and among its populations and the consequent exchange of alleles between geographically distant populations. The objective of this study was to examine reproductive compatibility between host-associated geographic populations of D. saccharalis in Argentina and to determine whether this pest represents a complex of host-associated cryptic species rather than a wide ranging generalist species. Intra and inter-population crosses revealed that D. saccharalis populations from the northwestern and Pampas regions presented evidence of prezygotic and postzygotic incompatibility. Such a result is likely to be the product of an interruption of gene flow produced by either geographic or host plant associated isolation, suggesting that Tucumán (northwestern) and Buenos Aires (Pampas) populations of D. saccharalis are a distinct genotype and possibly an incipient species.

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

“…A study by Fogliata et al. () on D. saccharalis populations collected from sugarcane and maize from the northwestern and Pampas regions in Argentina, revealed similar biological traits and some degree of pre‐zygotic and post‐zygotic incompatibility, when reared on artificial diet in the laboratory. Pre‐zygotic barriers imply impediments to the formation of zygotes (absence of a spermatophore in the reproductive tract of females) (Perfectti, ; Rhainds, ).…”

“…These barriers produced by for example geographic distance or host plant associations, interrupt the gene flow, generating reproductive incompatibility between populations. 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., ).…”

“…Pre‐zygotic barriers imply impediments to the formation of zygotes (absence of a spermatophore in the reproductive tract of females) (Perfectti, ; Rhainds, ). It is important to highlight that the number of spermatophores transferred by male SCB is generally one (Pérez & Long, ; Walker, ; Campos Guevara, ; Peairs & Saunders, ; Fogliata et al., ). Post‐zygotic barriers result from all those situations in which zygotes – and adult individuals if they complete their development – have practically nullified their biological effectiveness (lower fecundity and/or fertility, and/or sterile hybrids) (Perfectti, ; Rhainds, ).…”

“…As a follow‐up of studies by Fogliata et al. (), where they found that the barrier that interrupted the gene flow between the populations was geographic, we performed another survey of Argentina SCB populations collected from various host plants. This will allow to assess whether host plant association affects the evolution of reproductive isolation among SCB populations.…”

“…In addition, in this study we evaluated the isolation by geographical barriers, using distances shorter than the one studied by Fogliata et al. (). To address these concerns, three population combinations were considered: (1) populations from Tucumán and Jujuy provinces collected in sugarcane (geographically isolated), (2) populations from Tucumán and Jujuy collected in maize and sugarcane, respectively (isolated geographically and by host), and (3) two populations from Tucumán collected in sugarcane and maize (isolated by host).…”