The Complete Mitochondrial Genome of the Beet Webworm, Spoladea recurvalis (Lepidoptera: Crambidae) and Its Phylogenetic Implications.

Abstract

The complete mitochondrial genome (mitogenome) of the beet webworm, Spoladea recurvalis has been sequenced. The circular genome is 15,273 bp in size, encoding 13 protein-coding genes (PCGs), two rRNA genes, and 22 tRNA genes and containing a control region with gene order and orientation identical to that of other ditrysian lepidopteran mitogenomes. The nucleotide composition of the mitogenome shows a high A+T content of 80.9%, and the AT skewness is slightly negative (-0.023). All PCGs start with the typical ATN codons, except for COX1, which may start with the CGA codon. Nine of 13 PCGs have the common stop codon TAA; however, COX1, COX2 and ND5 utilize the T nucleotide and ND4 utilizes TA nucleotides as incomplete termination codons. All tRNAs genes are folded into the typical cloverleaf structure of mitochondrial tRNAs, except for the tRNASer(AGY) gene, in which the DHU arm fails to form a stable stem-loop structure. A total of 157 bp intergenic spacers are scattered in 17 regions. The overlapping sequences are 42 bp in total and found in eight different locations. The 329 bp AT-rich region is comprised of non-repetitive sequences, including the motif ATAG, which is followed by a 14 bp poly-T stretch, a (AT11 microsatellite-like repeat, which is adjacent to the motif ATTTA, and a 9 bp poly-A, which is immediately upstream from the tRNAMet gene. Phylogenetic analysis, based on 13 PCGs and 13 PCGs+2 rRNAs using Bayesian inference and Maximum likelihood methods, show that the classification position of Pyraloidea is inconsistent with the traditional classification. Hesperioidea is placed within the Papilionoidea rather than as a sister group to it. The Pyraloidea is placed within the Macrolepidoptera with other superfamilies instead of the Papilionoidea.