Geographic population structure of the sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), in the southern United States

Abstract

The sugarcane borer moth, Diatraea saccharalis, is widespread throughout the Western Hemisphere, and is considered an introduced species in the southern United States. Although this moth has a wide distribution and is a pest of many crop plants including sugarcane, corn, sorghum and rice, it is considered one species. The objective was to investigate whether more than one introduction of D. saccharalis had occurred in the southern United States and whether any cryptic species were present. We field collected D. saccharalis in Texas, Louisiana and Florida in the southern United States. Two molecular markers, AFLPs and mitochondrial COI, were used to examine genetic variation among these regional populations and to compare the sequences with those available in GenBank and BOLD. We found geographic population structure in the southern United States which suggests two introductions and the presence of a previously unknown cryptic species. Management of D. saccharalis would likely benefit from further investigation of population genetics throughout the range of this species.

Figure 1. Male genitalia of Diatraea saccharalis.

Adult male collected in Avoyelles, Louisiana from sugarcane by R T Richard. Adult is deposited in the National Museum of Natural History, Smithsonian Institute, Washington DC (USNM Slide #112, 735). Terminology is from Dyar and Heinrich (1927), an = anellus, chl = basal projection lobe from costa of harpe, cn = cornatus (or cornuti) of penis, gn = gnathos, j = juxta, ll = lateral lobe of tegumen, t = tegumen, u = uncus, v = vinculum. Photo edited by M Metz and M A Solis.

Figure 2. Structure 2.2 analysis depicts two genetically distinct clusters of D. saccharalis.

Individuals from southern Texas (S. Texas), eastern Texas (E. Texas) and Louisiana grouped together within the red cluster, while individuals from Florida grouped within the green cluster. The y-axis shows the probability of each individual to belong to a genetically distinct cluster. The number of individuals from each region used for the analysis is represented by ‘n’.

Figure 3. Neighbor joining phylogram of D. saccharalis populations.

The phylogram is based on a neighbor joining analysis of 658 bp of the COI barcode region. Bootstrap support values are based on 500 pseudoreplicates, and those above 80% are shown below supported nodes. Individuals collected as part of this study are shown in color: Florida in green; Texas/Louisiana in red. Individuals shown in black were obtained from GenBank and BOLD databases. See Table 1 for specimen details.