Iridopsis socoromaensis sp. n., a geometrid moth (Lepidoptera, Geometridae) from the Andes of northern Chile

Abstract Background Iridopsis Warren, 1894 (Lepidoptera: Geometridae: Ennominae: Boarmiini) is a New World moth genus mainly diversified in the Neotropical Region. It is represented in Chile by two described species, both from the Atacama Desert. New information Iridopsis socoromaensis sp. n. (Lepidoptera: Geometridae: Ennominae: Boarmiini) is described and illustrated from the western slopes of the Andes of northern Chile. Its larvae were found feeding on leaves of the Chilean endemic shrub Dalea pennellii (J.F. Macbr.) J.F. Macbr. var. chilensis Barneby (Fabaceae). Morphological differences of I. socoromaensis sp. n. with the two species of the genus previously known from Chile are discussed. A DNA barcode fragment of I. socoromaensis sp. n. showed 93.7-94.3% similarity with the Nearctic I. sanctissima (Barnes & McDunnough, 1917). However, the morphology of the genitalia suggests that these two species are distantly related. The discovery of I. socoromaensis sp. n. highlights the need for additional surveys in underexplored areas to understand better the taxonomic diversity and evolutionary relationships of the mainly Neotropical moth genus Iridopsis.


Introduction
The New World moth genus Iridopsis Warren, 1894 (Lepidoptera: Geometridae: Ennominae: Boarmiini) is mainly diversified in the Neotropical Region, from where 81 species have been described (Pitkin 2002, Vargas 2007, while 14 Nearctic representatives are known (Rindge 1966, Pitkin 2002. However, the taxonomic diversity remains insufficiently known in the Neotropical Region. For instance, 47 species were barcoded in a single small study area in southern Ecuador (Brehm et al. 2016). The genus is characterised morphologically by male genitalia with valva strongly divided into two lobes and the broad tegumen postero-laterally shaped like shoulders (Pitkin 2002). In a recent molecular phylogenetic study of the New World Geometridae, the species of Iridopsis, included in the analyses, clustered as a strongly-supported monophyletic group of the tribe Boarmiini sister to Neofidonia Warren, 1904(Perigramma Guenée, [1858] + Stenoporpia McDunnough, 1920 (Brehm et al. 2019).
Iridopsis is represented in Chile by two described species, both from the Atacama Desert: I. hausmanni Vargas, 2007 from the transverse valleys near sea level and I. parrai Vargas, 2007 from the Pampa del Tamarugal, a plain at about 1000 m elevation between the Pacific coast and the western slopes of the Andes. The larvae of the two species feed on leaves of their respective host plants; I. hausmanni on Haplorhus peruviana Engl. and Schinus molle L. (Anacardiaceae) (Vargas 2014), I. parrai on Prosopis tamarugo Phil. (Fabaceae) (Vargas 2007). A third species, discovered in the highlands of the Andes of the country, is described and illustrated here.

Materials and methods
The specimens examined were reared from folivorous larvae collected in March 2018 on Dalea pennellii (J.F. Macbr.) J.F. Macbr. var. chilensis Barneby (Fabaceae), near Socoroma Village at about 3300 m elevation on the arid western slopes of the Andes of northern Chile (18°16'41"S, 69°35'17"W). Genitalia dissections were performed using standard procedures. Images were captured with a Sony CyberShot DSC-HX200V digital camera attached to a Leica M125 stereomicroscope and a Micropublisher 3.3 RTV-QImaging digital camera attached to an Olympus BX51. The specimens studied are deposited in the "Colección Entomológica de la Universidad de Tarapacá" (IDEA), Arica, Chile.
One pupa was placed in ethanol (95%) and kept at -20°C to be used in genomic DNA extraction. This procedure was performed by staff of the "Laboratorio de Biología Molecular de Plantas" (Facultad de Ciencias Agronómicas, Universidad de Tarapacá, Arica, Chile) using the protocol described by Huanca-Mamani et al. (2015). DNA purification, PCR amplification and sequencing of the barcode fragment (Hebert et al. 2003) were performed in Macrogen Inc. (Seoul, South Korea) with the primers LEP-F1 and LEP-R1, following the PCR programme described by Hebert et al. (2004). Relationships of the obtained fragment were assessed using the BOLD Identification System (Ratnasingham and Hebert 2007).
Head. Vertex and frons mainly creamy white with scattered dark grey scales. Antenna filiform with scape and pedicel creamy white, flagellum dark grey. Labial palpus dark grey with a few scattered creamy white scales.
Thorax. Mainly creamy white with scattered dark grey scales. Legs with creamy white and dark grey scales intermixed. Forewing dorsal surface with whitish-grey and dark grey scales intermixed; lines and discal dot slightly differentiated; postmedial line dark grey, triangular from costal margin to M3, slightly differentiated to inner margin; subterminal line narrow, creamy white, continuous with an apical concolorous blotch with a few scattered dark grey scales. Forewing ventral surface mainly whitish-grey from base to postmedial line; discal dot dark grey; postmedial line dark grey, narrowing from costal margin to inner margin; subterminal line narrow, creamy white, continuous with a concolorous blotch at apex; mainly dark grey between subterminal line and outer margin, lighter to tornus. Hindwing dorsal surface similar to forewing, but without a creamy white blotch at apex. Hindwing ventral surface mainly whitish-grey with a small dark grey discal dot and dark grey postmedial line.
Abdomen. Mainly creamy white with scattered dark grey scales.
Female genitalia (Fig. 2). Papillae anales lobe-like with a few setae. Posterior apophyses narrow, elongated, about seven times the length of papillae anales, apex reaching the basal part of the ductus bursae. Anterior apophyses narrow, slightly shorter than half the length of the posterior apophyses. Lamella antevaginalis a fine transversal stripe with anterior margin convex and posterior margin concave. Ductus bursae cylindrical, sclerotised, slightly shorter than anterior apophyses. Corpus bursae oval, membranous, length about a third that of the ductus bursae, signum sub-circular with serrated margin and a few additional small projections on the central area. Ductus seminalis on distal third of ductus bursae.
Male. Similar to female in size and maculation, but with bipectinate antenna and hair pencil on metatibia.
Male genitalia (Fig. 3). Uncus triangular, round apex, with short setae near margin. Tegumen broad, anterior margin excavated in the middle. Saccus membranous ventrally. Juxta narrow, mainly as a longitudinal stripe; basal part semicircular slightly swollen antero-ventrally; apex excavated in the middle. Elongated hair-like scales near base of juxta. Valva deeply cleft; costal lobe wide, dorsal margin mainly straight, apex round, ventral process slightly curved outwards; sacculus triangular, apex round, internal face with a slightly differentiated longitudinal fold near apex. Phallus subcylindrical, about twice the length of the costal lobe of the valva, anterior part slightly downward-curved; a narrow, elongated cornutus on the vesica, slightly smaller than half the phallus length.
DNA barcoding. One sequence of DNA barcode (GenBank accession MW261921) of 658 bp was obtained. The BOLD Identification System found 93.7-94.3% similarity with the Nearctic I. sanctissima (Barnes & McDunnough, 1917), while similarity was 93.1% with the only haplotype of a Chilean congeneric (I. hausmanni) available in BOLD.

Diagnosis
Iridopsis socoromaensis sp. n. is recognisable by the dorsal surface of forewing with postmedial line like a dark grey triangle from the costal margin to M3 and an apical creamy white blotch with a few scattered dark grey scales, the female genitalia with lamella antevaginalis as a fine transverse stripe and the male genitalia with the costal lobe of the valva with a ventral process slightly curved outwards and the vesica with a single cornutus. In contrast, the two other Chilean representatives (I. hausmanni and I parrai) lack a dark grey triangle and apical creamy white spot on the forewing dorsal surface, lamella antevaginalis in the female genitalia and ventral process of the costal lobe of the valva in the male genitalia and the vesica has multiple cornuti. DNA barcode divergence with the only currently-available haplotype of I. hausmanni was found to be 93.1%. DNA barcode sequences of I. parrai remain unknown impeding comparisons.

Etymology
The specific epithet is derived from Socoroma Village, the type locality of I. socoromaensis sp. n.

Distribution
Iridopsis socoromaensis sp. n. is known only from the type locality near Socoroma Village in the Andes of northern Chile (Fig. 4).

Biology
The folivorous larvae of I. socoromaensis sp. n. were recorded on the Chilean endemic Dalea pennellii var. chilensis (Fig. 5), a fabacean prostrate shrub inhabiting a narrow elevation range between about 2500 and 3300 m and 18° and 20° S on the western slopes of the Andes (Rodriguez et al. 2018).

Discussion
The Neotropical Region harbours a higher number of species of Geometridae than any other biogeographic region (Brehm et al. 2019). The wet tropical Andes are recognised as the main global diversity hotspot of this family, based on studies undertaken in southern Ecuador (Brehm et al. 2005, Brehm et al. 2016. In contrast, few species of Geometridae are known from the arid western slopes of the Andes of southern Peru and northern Chile. However, the recent discovery of I. socoromaensis sp. n. and other species (Cerdeña et al. 2019, Palacios et al. 2020 suggests that native plants of these high elevation environments support an insufficiently-known fauna of geometrid moths. Iridopsis socoromaensis sp. n. is the third species of the genus described from Chile. Although the phylogenetic relationships of the species of Iridopsis remain unknown, the morphology of the genitalia suggests a distant relationship between I. socoromaensis sp. n. and the two other Chilean representatives of the genus: I. hausmanni and I. parrai. In contrast, a close relationship between the latter two was suggested, based on some morphological characters of the male genitalia (Vargas 2007). Although DNA barcodes of I. sanctissima were the most similar to the sequence of I. socoromaensis sp. n., the similarity is lower than between closely-related species of Geometridae (e.g. Hausmann et al. 2009, Hausmann andHuemer 2011). Furthermore, the morphology also rules out a close relationship between them, because I. sanctissima has a distal cleft on the uncus, lacks a ventral process on the costal lobe, has a curved sacculus and vesica with several small cornuti, suggesting, instead, a close relationship with I. clivinaria (Guenée, 1857), another Nearctic congeneric (Rindge 1966). Additional surveys for geometrid moths in the arid high elevation environments of the Andes and other little explored environments of the Neotropics would be needed to find congeneric species close to I. socoromaensis sp. n.
Host plants remain unknown for a great number of species of Neotropical Geometridae. The available data suggest that host ranges are variable amongst species (Brehm 2002, Brehm 2003, Bodner et al. 2010. Although the Neotropical Region harbours the highest diversity of Iridopsis (Pitkin 2002), host plants are documented only for a few species involving a wide range of plant families (Brehm 2002, Brehm 2003, Vargas 2007, Vargas 2014, Marconato et al. 2008, Bodner et al. 2010, Robinson et al. 2010. A relatively-narrow host range has been suggested for I. hausmanni, with its only two records restricted to Anacardiaceae trees (Vargas 2014), while a wide host range has been described for the polyphagous I. herse (Schaus, 1912), whose larvae feed on plants of at least 17 families (Brehm 2002). Fabaceae host plants like I. socoromaensis sp. n. have, so far, been recorded for five other species of Neotropical Iridopsis (Brehm 2002, Vargas 2007. The four specimens of I. socoromaensis sp. n. studied here lasted eleven months as pupae, from April 2018 to March 2019, suggesting pupal dormancy. Duration of the pupal stage from a few weeks to 27 months was described for another geometrid moth (Eupithecia tarapaca Rindge, 1987) that inhabits the same area (Vargas 2016). A long pupal duration with adult emergence around March (end of summer and beginning of autumn) in I. socoromaensis sp. n. could ensure abundant leaves of the host plant for larvae of this species, as the highest vegetation cover occurs after the summer rains in the study site (Muñoz and Bonacic 2006). However, additional observations are needed to understand better the natural history of I. socoromaensis sp. n. in the arid high elevation environments of the Andes.