Reassessment of the status of Lymantria albescens and Lymantria postalba (Lepidoptera: Erebidae: Lymantriinae) as distinct ‘Asian gypsy moth’ species, using both mitochondrial and nuclear sequence data

Abstract

For regulatory purposes, the name ‘Asian gypsy moth’ refers to a group of closely related Asian Lymantria species and subspecies whose female moths display flight capability, a trait believed to confer enhanced invasiveness relative to the European gypsy moth, Lymantria dispar dispar, whose females are flightless. Lymantria albescens and Lymantria postalba are Asian gypsy moths occurring in the southern Ryukyu Islands and in the northern Ryukyu and adjacent Kyushu and Shikoku Islands of Japan, respectively. Although once considered subspecies of L. dispar, their status as distinct species, relative to the latter, is now well established. While postalba was subsequently considered a subspecies of L. albescens, largely on the basis of differences in forewing ground colour in males, both taxa were later given distinct species status by Pogue & Schaefer (2007) following their revision of the genus Lymantria. Here, we re‐examined the validity of this revised status through the sequencing of a large portion of the mitochondrial genome (c. 60%) and multiple nuclear marker genes [elongation factor 1‐alpha (Ef‐1α), wingless (Wgl), internal transcribed spacer 2 (ITS‐2), ribosomal protein S5 (RpS5)] in representative specimens of both taxa and other Lymantria species, including L. monacha, L. xylina, L. mathura and members of the L. dispar + L. umbrosa clade. A comparison of the number of substitutions in these genomic regions among the taxa we considered showed lower or equivalent variation between L. albescens and L. postalba compared with subspecies of L. dispar, for mitochondrial and nuclear sequences, respectively. This finding was reflected in the maximum likelihood trees generated independently for mitochondrial and nuclear data, where L. albescens and L. postalba formed, in both analyses, a short‐branch sister clade basal to the L. dispar + L. umbrosa clade. We further sequenced three markers [cytochrome c oxydase 1 (COI), EF‐1α, Wgl] in multiple L. albescens–L. postalba specimens collected along a south‐to‐north transect across the Ryukyu Arc and observed no clear distinction among the sampled specimens as a function of taxonomic designation. We conclude that L. albescens and L. postalba form a single species, with postalba representing a darker‐winged morph along an apparent south‐to‐north wing colour cline. Accordingly, L. postalba is relegated to synonymy under L. albescens (syn.n.).

Improvement in the Identification Technology for Asian Spongy Moth, Lymantria dispar Linnaeus, 1758 (Lepidoptera: Erebidae) Based on SS-COI

“…Our findings revealed that L. postalba and L. albescens are closely related, with a genetic distance between them based on COI fragments of 0. The taxonomic status of the two species remains controversial, with some researchers arguing that “ L. albescens and L. postalba are at best two forms of a single species” [ 63 ]. Similarly, we found that the genetic distance between L. apicebrunnea and L. schaeferi based on COI fragments was also 0.…”

Potential Differences and Methods of Determining Gypsy Moth Female Flight Capabilities: Implications for the Establishment and Spread in Novel Habitats

“…However, easily observed morphological differences between subspecies are minimal [64]. Genetic methods of identification have been developed which help to differentiate between subspecies and populations [65][66][67] and therefore aid in determining flight capability and potential flight distance.…”

Range‐wide population genomics of the spongy moth, Lymantria dispar (Erebidae): Implications for biosurveillance, subspecies classification and phylogeography of a destructive moth

“…These authors recognized three subspecies of L. dispar , namely (i) L. dispar japonica , found on the main islands of the Japanese archipelago, including the western portion of Hokkaido, (ii) L. dispar asiatica , present in continental Asia, from the Ural Mountains to the Russian Far East, with a high prevalence in eastern China and South Korea, and (iii) L. dispar dispar , observed in Europe, west of the Ural Mountains, north Africa and eastern North America. Along with two closely related Lymantria species found in eastern Hokkaido ( L. umbrosa ) and the Japanese Ryukyu Islands ( L. albescens ; see Djoumad et al, 2020 , for a recent taxonomic revision), the two Asian subspecies of L. dispar are now collectively referred to as Asian spongy moths, largely on the basis of a shared biological trait believed to confer greater invasive propensity, that is female flight capability. In comparison, females of L. dispar dispar , now referred to as European spongy moths, are flight‐incapable.…”