Grammia, Rambur, 1866

Schmidt, B. Christian, 2009, Taxonomic revision of the genus Grammia Rambur (Lepidoptera: Noctuidae: Arctiinae), Zoological Journal of the Linnean Society 156 (3), pp. 507-597 : 509-511

GRAMMIA BIOLOGY

Nearly all (36/37) species of Grammia occur in North America, with only one species ( Grammia kodara Dubatolov & Schmidt ) restricted to the Palaearctic, and two species ( Grammia quenseli Paykull and Grammia philipiana Ferguson ) occurring in both the Palaearctic and Nearctic regions. The genus reaches its greatest diversity in the grasslands of the Great Plains and the southern Rocky Mountain region, although the genus has a transcontinental distribution, occurring from the Arctic coast to central Mexico. Dry, sparsely treed biomes are preferred Grammia habitats, including tundra, open forest, rocky slopes, grasslands, barrens, sand dunes, and gravelly or rocky substrates. Although most western North American species occur at low to moderate elevations, several species occur only in alpine and arctic habitats. Relatively few species have distributions exclusive to eastern North America, but these species are again usually associated with dry, open forest habitats such as oak/pine barrens and poor or shallow soils such as sand hills, beaches, granite balds, and alvars. A few species are common in mesic and wetland habitats. Unlike many other Arctiinae , Grammia larvae are not host-specific; despite this, many species are very local in occurrence, probably limited by microhabitat variables such as vegetation cover and soil substrate type. The dark-coloured, densely setose larvae, which feed on low-growing plants, exhibit typical adaptations to cold, arctic, and alpine environments, and are one of only a few arctiine genera to occur in arctic–alpine habitats ( Ferguson, 1985).

Grammia species rarely reach high population densities and are therefore not important from an economic perspective, and detailed knowledge of their life history remains fragmentary. Notable exceptions to this are Grammia blakei (Grote) and Grammia incorrupta (Hy. Edwards) . Grammia blakei larvae can occasionally reach densities high enough to cause minor damage to spring crops in the northern Great Plains, and aspects of G. blakei ’s biology were published by Byers (1988, 1989). The ecology of G. incorrupta larvae has received considerable attention (e.g. Singer, 2000; Singer & Stireman, 2001, 2003; Bernays & Singer, 2005) in light of herbivory patterns and interactions between plant compounds and larval parasitoids, stemming from the work of Singer (2000).

Little is known about the reproductive ecology of Grammia . Use of female pheromones in mate attraction has been documented in G. blakei ( Byers, 1988) and Grammia arge (Drury) ( Conner, Webster & Itagaki, 1985) , and this is presumably the norm for the genus. Conner et al. (1985) described the rhythmic pulsing of the abdomen in G. arge during pheromone emission, behaviour that is similar to other members of the tribe ( Conner et al., 1985; pers. observ.). Onset of calling behaviour in G. arge occurs about 5.5 h after dark ( Conner et al., 1985). The female pheromone gland is located dorsally between abdominal segments 8 and 9, and pulsing of the abdomen is associated with expulsion of liquid pheromones from this gland ( Bendib & Minet, 1998). It is not known if male pheromones exist in Grammia , and if these play a role in courtship. The complex male coremata (pheromone-dispersing structures used in courtship) of other arctiine species (reviewed by Weller, Jacobson & Conner, 1999) are highly reduced in Grammia , and do not appear to be functional. The chemical precursors associated with male pheromones in other arctiids, hydroxydanaidal, is absent in G. incorrupta ( Hartmann et al., 2005) . Similarly, the microtymbals [thoracic sound-producing structures used in acoustic aposematism and courtship ( Weller et al., 1999)] are simplified in Grammia , although still functional ( Fullard & Fenton, 1977). Absence of the tymbal microstriae appears to be a secondary loss rather than a primitive character ( Weller et al., 1999).

Females lay between several hundred and a thousand eggs; these lack adhesive, and are laid haphazardly among ground litter ( Singer, 2000), or are attached indiscriminately to available substrates (pers. observ.). Fully gravid females are likely to be very poor fliers, and eggs are laid while the females are on the ground ( Singer, 2000). Larvae are highly polyphagous on herbaceous plants, but prefer dicots; G. incorrupta feeds on over 80 plant species in 50 families under natural conditions, regularly changing host species throughout the course of a single day ( Singer, 2000). Parasitism of larvae by tachinid flies and hymenopterans has been shown to induce a preference for plants containing pyrolizidine alkaloids ( Bernays & Singer, 2005), compounds which are detrimental to the parasitoid ( Singer & Stireman, 2003), and as such the larvae are able to self-medicate when parasitized. Grammia incorrupta possesses the ability to detoxify and store all types of pyrolizidine alkaloids occurring in its environment ( Hartmann et al., 2005), a process mediated by an enzyme thought to be present in the ancestor of the Arctiini ( Weller et al., 1999) . Like many other arctiines studied to date, larval G. incorrupta are able to convert and store plant-derived pyrolizidine alkaloids, conferring chemical protection to the adult stage ( Hartmann et al., 2005).

Adults of Grammia are relatively short lived (1–3 weeks; Singer, 2000) as mouthparts are nonfunctional. In contrast, larvae tend to be relatively longlived because they overwinter in the mid to late instars ( Byers, 1988; Singer, 2000). Instar number is variable in G. incorrupta , generally with seven or eight instars, but with as many as 12 ( Singer, 2000). Grammia blakei larvae go through seven instars ( Byers, 1988). Although most Grammia species undergo a single generation per year, some species (e.g. G. incorrupta , G. arge , G. figurata ) have multiple yearly broods. Pupation occurs in or near the soil surface amongst debris or loose soil in a flimsy cocoon ( Byers, 1988; Singer, 2000; pers. observ.). The dense setation and high motility of larvae functions as an escape mechanism from predators such as ants, ground beetles, and wasps ( Singer, 2000), with the highest larval mortality a result of parasitism by tachinid flies ( Singer, 2000; Stireman & Singer, 2002). Larvae actively feed during the day, seeking shelter during the hottest hours, and much time is spent resting on the ground ( Singer, 2000; pers. observ.).

OVERVIEW

The purpose of this study was to review the generic limits and revise the species-level taxonomy of Grammia using an integrative taxonomy approach ( Dayrat, 2005) by combining morphology, wing pattern, ecology, biogeography, and cytochrome oxidase I ( cox 1) sequence data, to facilitate further systematic and ecological work on this diverse genus. Although genitalic morphology in Grammia has been of limited use in discriminating closely related species ( Smith, 1938a), prior study has largely been limited to external male genitalia. Here, I expand the morphological character set to include the everted male vesica, female genitalia, and eye and antennal structure. As a result of the paucity of morphological characters traditionally used to delineate Grammia species , and the relatively large number of species available for sampling, Grammia is an ideal candidate group to test the utility of species-level molecular taxonomy. Mitochondrial DNA nucleotide sequence data have proven useful in resolving species problems by providing additional characters with which to assess species delimitations ( Simon et al., 1994; Caterino, Cho & Sperling, 2000), particularly the cytochrome oxidase gene regions I and II ( cox 1, cox 2) in Lepidoptera ( Caterino et al., 2000; Sperling, 2003a). The species-level diagnostic power of cox 1 has resulted in ‘DNA barcoding’ initiatives across a wide range of animal taxa ( Hebert et al., 2003), although not without its limitations ( Lipscomb, Platnick & Wheeler, 2003; Sperling, 2003b; Will & Rubinoff, 2004; Gompert et al., 2006; Linnen & Farrell, 2007). Molecular sequence data of the mtDNA cox 1 gene proved to be of limited taxonomic value within Grammia , because even morphologically divergent species exhibited shared or similar (<0.5% divergence) haplotypes. With the exception of nine haplogroups that were consistent with species concepts based on all other taxonomic characters, mtDNA paraphyly was extensive. This significant discrepancy between morphological/biological cohesiveness and mtDNA is examined in detail elsewhere ( Schmidt, 2007; Schmidt & Sperling, 2008).

Grammia is revised to include 37 species, including 14 subspecies. Holarctia obliterata (Stretch) is also included in this study because it has previously been treated as a subgenus of Grammia ( Schmidt & Opler,

2008). Six species are described as new, Grammia margo sp. nov., Grammia yukona sp. nov., Grammia brillians sp. nov., Grammia fergusoni sp. nov., Grammia yavapai sp. nov., and Grammia ursina sp. nov. Three new subspecies are proposed, Grammia speciosa celineata ssp. nov., Grammia virgo gigas ssp. nov., and Grammia nevadensis vivida ssp. nov. Neotypes are designated for Callimorpha parthenice Kirby , Callimorpha virguncula Kirby , Arctia williamsii Dodge , and Arctia edwardsii Stretch. Lectotypes are designated for Euprepia gelida Möschler , Arctia speciosa Möschler , Arctia quadranotata Strecker , Arctia oithona Strecker , Arctia incorrupta Hy. Edwards , Apantesis tooele Barnes & McDunnough , and Arctia favorita Neumögen. Arctia celia Saunders is revised to synonymy under Grammia figurata (Drury) , and Grammia franconia (H. Edwards) is raised to species status. Apantesis favorita ab. favoritella Strand is revised to synonymy under Grammia phyllira (Drury) .