Grammia yukona, 2009

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 : 548-549

GRAMMIA YUKONA SCHMIDT SP. NOV. ( FIGS 23, 116 )

Grammia geneura (Strecker) ; Lafontaine & Wood, 1997: 738.

Type material: Holotype ( Fig. 23) – ♂. Canada, YT, Kusawa Lake , north shore, 60°36.24′N 136°8.04′W, 800 m, 27.vi.2004, rocky sage/juniper slope, B.C. Schmidt [ CNC] . Paratypes – 7 ♂♂, 1 ♀. YT: same data as holotype , 5 ♂♂ [ BCSC]; Klondike Hwy , 10 km south Moose Creek, 4.vii.1981, C. Dondale, sage slope [reared] , 1 ♂ [ CNC]; Klondike Hwy , km 572, UVL at edge of marsh, 63°32′N, 137°08′W, 7.viii.1980, #800145 ROM Fld. Pty ., 1 ♂ [ CNC]; Richardson Mtns , 67°58′N, 136°29′W, 28–30.vi.1987, M. Polak and M. Wood [reared] , 1 ♀ [ CNC] .

Etymology: This species is currently only known from YT, hence the name.

Diagnosis: Very similar to G. nevadensis superba , but smaller with paler, washed-out colours, particularly the thorax underside, which is buff-coloured in G. yukona , compared to yellow in G. nevadensis . Eye size and antennal branch length averages smaller in G. yukona than in G. nevadensis , and the geographical ranges of the two do not overlap. Grammia yukona flies about one month earlier than the northernmost G. nevadensis populations. See also ‘Remarks’ below for discussion of the relationship to G. nevadensis .

Description: Male: Head – Vestiture, colour, and antennal structure similar to and as described under G. nevadensis . Antennal scales predominantly dark brown, with at least some pale buff scales along dorsal side in five out of nine specimens; longest antennal branches averaging 4.76 ¥ 10 - 1 mm, 3.2¥ intersegmental distance (N = 6). Eye diameter at widest point averaging 6.61 ¥ 10 - 1 mm (N = 7). Thorax – Underside pale buff to yellow-buff, paler than the yellow seen in other nevadensis populations, the alldark thorax form is not exhibited in the type material, and like northern populations of ssp. superba , probably does not occur. Colour and vestiture otherwise as described under G. nevadensis . Abdomen – Pattern and colour as for G. nevadensis , except that the dorsal ground colour tends to be paler, varying from yellow-buff to pale orange. Forewing – Average forewing length 15.3 mm (N = 7). Overall pattern and colour similar to G. nevadensis superba . Hindwing – Dorsally, ground colour yellowish-buff to pale orange, postmedial and subterminal dark markings tending to be fused more so than in superba . Underside colours more washed out, and lacking the flush of yellowish basal scales evident in superba and vivida. Genitalia – Indistinguishable from those of G. nevadensis ; distal portion of valve tapering to apex, apex rounded; clasper reduced; median ridge moderately developed; uncus broad-based, process evenly tapered to point, 2.3¥ longer than width of base; juxta slightly wider than long; aedeagus with dorsad curve at 2/3 distance beyond base; distal chamber of vesica kidney-shaped, coarsely scobinate; medial chamber 1/2 as wide as length of distal chamber, moderately scobinate; diverticula moderately developed.

Female: Only known from one reared specimen, which has crumpled, incompletely expanded wings. The ventral thoracic and leg vestiture is rubbed, but based on the wing pattern and colour, it is very similar to female G. n. superba . Most of both antennae are missing; antenna moderately biserrate, as in G. nevadensis .

Biology: The habitat of G. yukona , where known, is dry, rocky, or eroding south-facing slopes, characterized by grasses, Artemisia L., and Juniperus horizontalis Moench. Adults have been collected between late June and early August. Adults are attracted to light, but because of the brief dark period of northern summers, yukona may also be day-active.

Distribution: Known from three localities in YT: the Richardson Mountains in the north-east, the Klondike Highway in central YT, and Kusawa Lake near the BC border ( Fig. 116 ).

Molecular variation: Two sequenced specimens from the type locality show identical haplotypes, and are at least 3.5% divergent from all sampled G. nevadensis populations ( YK 1; Fig. 134 ). Although this level of divergence is indicative of species-level differences, the extensive mtDNA polyphyly within the genus, and the fact that two specimens of YT G. quenseli showed identical or very similar haplotypes ( YK 1, QE3; Fig. 134 ) illustrate that mtDNA does not provide conclusive evidence of the specific distinctness of yukona . Nevertheless, no haplotypes were shared with the geographically nearest populations of nevadensis from west-central AB and central BC, suggesting that there is no gene flow between these populations, and that yukona is truly disjunct.

Remarks: Grammia yukona is closely related to G. nevadensis . However, I believe that the large range segregation, morphological differences, and genetic distinctness of G. yukona are best interpreted as species – rather than subspecies – level differences, particularly in light of the Beringian glacial history. The northernmost populations of G. nevadensis in central BC and west-central AB (Peace River canyon) approach G. yukona in appearance in that they are smaller with duller colours compared to nominate G. nevadensis superba and G. nevadensis vivida . The range restriction of G. yukona to the Beringian ice age refugium in dry grassland-steppe habitat so prevalent during the last glacial maximum, and the genetic divergence from G. nevadensis , indicate that G. yukona is likely to be a Beringian glacial relict, derived from G. nevadensis populations to the south.

Figures

Figure 134. Neighbour-joining tree of Western lineage haplotypes of Grammia species. Multiple symbols per row indicate multiple species and/or samples for a given haplotype. Squares indicate species with haplotype complements primarily or exclusively in the Western lineage, circles indicate predominantly Eastern lineage species. Grammia virgo haplotype VI15 (triangle) is the sole G. virgo haplotype outside of the Virgo lineage.

Figures 114–119. Distribution of examined specimens of Grammia.