Dirce oriplancta, Turner, 1925

Young, Catherine J., 2006, Molecular relationships of the Australian Ennominae (Lepidoptera: Geometridae) and implications for the phylogeny of the Geometridae from molecular and morphological data, Zootaxa 1264 (1), pp. 1-147 : 1-147

Dirce oriplancta and Dirce sp.

D. oriplancta and the undescribed Dirce sp. are also strongly supported as sister species (Fig. 10) and sequence divergence between the two species = 0.3% (28S D2) (Appendix 6). As with D. lunaris and D. solaris these diurnal species are sympatric and fly in early summer. They appear to be limited in distribution to Mt Field in southern Tasmania although this is most likely an artefact of under­collection. The larvae feed on the prostrate alpine conifers Microstrobos niphophilus Garden & Johnson (Podocarpaceae) and Diselma archeri Hook. f. ( Cupressaceae ) during the autumn months. There is also an unconfirmed record of D. oriplancta feeding on Leptospermum sp. (Myrtaceae) (P. B. McQuillan. pers. comm.). In this case, D. oriplancta is usually the dominant species. Both species are moderately small, are cryptically coloured and are rather dull in colouration and are, thus, superficially similar in appearance. These moths lack the flash colouration present on the hindwings of lunaris and solaris .

The two species share the following characteristics:

Male genitalia (Figs 51–54)

—moderately long, narrow, acute uncus with narrow base; small, pendulous and slightly sclerotised socii; large gnathos, D. oriplancta with simple apex devoid of spines, apex of gnathos with brush­like spines in Dirce sp. ; valvae simple except costa in Dirce sp. extended proximally, posteriorly, to form lobe­like projection; processes of the anellus large, well­developed in both species, not articulated to juxta, processes in oriplancta , pouch­like very similar to those in lunaris ; juxta, small; aedeagus, curved, apically acute.

Female genitalia (Figs 55, 56)

—broad ovipositor; short, rather broad, membranous, ductus bursae; large, membranous corpus bursae; large, flattened stellate signum.

Immature stages

The eggs of these two species are almost identical (Figs 57, 58) except that the chorion in Dirce sp. is rough, wrinkled and cobbled (Fig. 60) instead of smooth and undulating as in D. lunaris and D. oriplancta (Fig. 59).

Larvae

The larvae of these two species are very similar to lunaris and solaris and share the characteristics described above.

D. aesiodora as basally derived in Dirce

D. aesiodora is moderately supported as a basal element in Dirce (28S D2) (Fig. 10) and was also strongly linked to D. lunaris by EF 1­ data (distance = 3.8%) (Fig. 12) and the combined molecular data set (Fig. 15). D. aesiodora is the largest of the Tasmanian Archiearinae . The adult is moderately small. Forewings are cryptically coloured and patterned in shades of brown, grey and white. The hindwings have flash colouration consisting of a large yellow spot encircled in dark greyish brown, similar to lunaris and solaris . The female is slightly larger than the male and the colouring of its hindwings more intense. Distances (28S D2) between aesiodora and its congeners were the highest in the genus and ranged from 2.2% between this species and Dirce sp. to a uniform 1.8% between aesiodora and the other species (Appendix 6). Similar to its congeners, this species flies early in summer but unlike other Dirce sp. , the larvae feed on Athrotaxis cupressoides D. Don (Pencil Pine) (Cupressaceae) and A. selaginoides D. Don (King Billy Pine) (similar to Acalyphes philorites see below), again through the autumn months. Interestingly this family of gymnosperms is confined to the Northern Hemisphere apart from this single genus ( Curtis & Morris 1975). D. aesiodora occurs on the Northern Central Plateau, as far west as Cradle Mountain and south to Mt Field in Tasmania. However adults are difficult to intercept and the species is likely to be under­collected, resulting in under­estimation of its distributional range.

D. aesiodora is very similar morphologically to its congeners but has several singular characteristics that support its placement as a sister species to the rest of the genus.

Male genitalia (Fig. 61)

—relatively long and narrow uncus; sclerotised anal tube; widened valvulae; processes of the anellus, short and wide.

Female genitalia (Fig. 62)

—signum is large and flattened (as in congeners) but the stellate edges are more pronounced and form tooth­like projections.

Larvae (Fig. 63)

The main features of the aesiodora larvae are identical to its congeners (described above) however these larvae are distinctively long, slender and pink in colour, greatly resembling the mature leaves of Athrotaxis D.Don. It is interesting that aesiodora feeds on the same hostplant as Acalyphes philorites , possibly indicating that Cupressaceae may be an ancestral hostplant family for the Tasmanian Archiearinae . In that case D. lunaris and D. solaris , as a more derived clade in Dirce , have captured, by colonization, foodplants from two unrelated angiosperm families the Epacridaceae and possibly the Myrtaceae as hostplants. However this sequence of events assumes monophyly of the Tasmanian Archiearinae ; a hypothesis not well supported by molecular characters. By comtrast the monophyly of the Tasmanian Archiearinae is moderately well supported by the morphological analysis (Fig. 16) (see discussion below under Monophyly of the Tasmanian Archiearinae ).

Monophyly of Dirce

Morphologically the group is homogeneous and species share the following characters:

Male genitalia (Figs 44–47, 51–54, 61)

—simple, straight, narrow, acute uncus; small, slightly sclerotised, pendulous socii; well­developed gnathos; well­developed transtilla consisting of two lobes; simple valvae; small juxta; processes of the anellus, but variable in shape and size; aedeagus, usually curved, with long, rod­like cornuti attached to the vesica.

Female genitalia (Figs 48, 49, 55, 56, 62)

—wide ovipositor; sclerotised lamella postvaginalis; narrow, sclerotised lamella antevaginalis; small sclerotised colliculum; membranous or sclerotised, moderately long, rather broad ductus bursae; large, membranous corpus bursae; large, flattened, signum with stellate edges, except absent in D. solaris .

Eggs (Figs 57–60) ( Young 2006, in press)

Eggs of D. lunaris , D. oriplancta and Dirce sp. are very similar. They are moderately broad, bluntly ovoid eggs with generally barely discernible cell form. However the micropylar cells are well marked with narrow and shallowly reticulated cell walls. The aeropyles are very small and inconspicuous with extremely small openings. The chorion of the eggs of D. lunaris and D. oriplancta is smooth and undulating but rough, wrinkled and cobbled in Dirce sp. , similar to that of Acalyphes sp.

Larvae (Figs 50 & 63)

Larvae are described under D. lunaris and D. solaris ; however none of the larval features are apomorphic for the genus and larvae are typically ennomine.

Pupae

The pupae of all Dirce species , apart from solaris , were available for examination. Pupae of these species were almost identical and had the following characteristics:

—smooth cuticle; exposed, moderately large labium; fore­femora concealed; tips of meta­tibiae well exposed, appearing relatively large and pendulous; small pro­thoracic spiracle; moderately long setae; absence of spiracular groove or flange plate on A5; very small, shallow, randomly, densely distributed, punctures on A1–8; deep, well­developed dorsal groove between A9 and A10; weak lateral groove; cremaster bifurcate, terminal setae long, robust, hamate, apically convergent.

The monophyly of Dirce is secure on the basis of molecular data and also homogeneity in morphological characters. The 28S D2 data places Dirce within the Australian Nacophorini , however this relationship is unsupported (Fig. 10), but is strengthened by the combined gene analysis (Fig. 15) albeit with a much reduced dataset. Possible synapomorphies for the genus that separate it from the Nacophorini are as follows:

—absence of extra larval prolegs; flattened stellate signum; bifurcate cremaster; moderately long pupal setae.

The processes of the anellus in Dirce are distinguished from similar articulated structures in Acalyphes by their fusion with the juxta.

Despite the presence of distinctive morphological features in Dirce , the genus shares several characteristics with some of the Australian Nacophorini . Dirce is differentiated from most of the Australian Nacophorini by the absence of extra prolegs in the larvae; however this is also the case in the Australian nacophorines Amelora Guest , Corula Walker , Furcatrox McQuillan , Cassythaphaga McQuillan , Ciampa Walker and Chlenias Guenée. The flattened, stellate signum was also uncommon in this analysis and absent in the Nacophorini , apart from a similar but reduced structure in Corula ; however similar structures were also present in the New Zealand ennomine D. floccosa , the larentiine Euphyia nr. severata, the oenochromines s. l. Dichromodes euscia and Nearcha and the Holarctic archiearine Archiearis . Dirce also shares a bifurcate cremaster with Archiearis ; however in Archiearis the setae are arranged in a T­shape, similar to Alsophila Hübner ( Nakamura 1987; Patočka & Zach 1994) (see discussion above) unlike the parallel setae of Dirce . Bifurcate cremasters are uncommon in the Australian Nacophorini and were only recorded in Capusa , Corula and Cycloprorodes Turner in this study and also Cassythaphaga petrochroa ( McFarland 1988) and Amelora leucaniata (McQuillan 1996) . All of these species apart from Capusa are more similar to Dirce in having long robust and mostly parallel cremastral setae whereas, in Capusa , the terminal setae are of the Alsophila type being small, slender and diverging immediately at right angles to the cremaster.

Given the sharing of this pupal feature and also the absence of extra larval prolegs, characteristics both uncommon in the Australian Nacophorini , it is possible that Dirce is closely related to this group of genera i.e. Amelora , Cassythaphaga and Furcatrox [the Amelora group, in part ( McQuillan 1986)]. This latter clade is moderately well supported by both molecular and morphological evidence. Interestingly, as Dirce has been recorded feeding on Epacridaceae , Myrtaceae , Podocarpaceae and Cupressaceae , this group of taxa is also polyphagous. This inclusion by Dirce of both gymnoperms and angiopsperms as host plants is unusual in Lepidoptera ( Holloway & Herbert 1979) . The feeding of Corula on Cupressaceae , similar to Dirce sp. and D. oriplancta , and the sharing of a similarly structured signum and cremaster may also support an association between these genera.

Nevertheless the bifurcate condition is typical of Boarmiini , Macariini , Cassymini and Eutoeini (Hollway 1994) and is also characteristic of the Oenochrominae s. str. (see discussion above). Moderately long setae were also a common feature in the pupae of Boarmiinae examined in this study whereas very short pupal setae are characteristic of the Australian Nacophorini (data not shown). Superficial similarities with the Holarctic Archiearinae such as diurnal­type eyes, heightened melanism, hairiness and brightly coloured hindwings in some species are most likely due to convergence in adaptations to a diurnal habit and a cold environment.