Neotypus (designated here): Chile. Reg. de Aysén: Prov. de Capitán Prat, Reserva Nacional Katalalixar, Isla Campana, Angostura Chilena, creciendo en turbera de Donatia–Astelia, [48°34'01”S 75°13'46”W ], 31 m, 9.I.2023, Saldivia & Faúndez 4211 (MURAY [MURAY-BV02090]!; isoneo-: SGO!). Holotypus: Chile. Reg. de Aysén: insulis Chonos [Chonos Archipelago], c. 245 m, s.d., Fonk (not located).

Annual herbs, 17–22 mm tall. Stems purplish, glabrous, or with sparse eglandular trichomes, erect, unbranched, with 2–3 nodes with well-developed leaves and 2 with underdeveloped leaves towards the apex. Cotyledons 2 mm long, green, oblong, entire, persistent. Leaves opposite, sessile, obovate, base truncate to slightly cuneate, succulent, 3–5-lobed; upper lobes with margin bluntly broad-obtuse, thickened and cucullate, papillose in the abaxial surface (visible only after dissection when cucullate area is unfolded) and scaberulous in the adaxial surface, lobes green, blade upper portion green and purplish towards the nodes; leaves from the first node 3 × 1.8 mm, 3-nerved, one apical lobe and two diminutive lateral ones (one in each side of the blade); leaves of the second node 4 × 2.5 mm, with lateral lobes more developed, 5-nerved; the leaves from the third node reach the largest size, 4.2 × 2.8 mm, 5-lobed, one apical and two lateral on each side of the blade decreasing in size towards the base; bracts like the leaves from the second node but narrower. Flowers axillary, sessile, acropetally, and decussately developed in the second and third nodes; above that, only small undeveloped buds in the axils of the apical congested underdeveloped leaves. Calyx 3.5 × 1.5 mm (3.5–4 mm when dissected), green and purplish towards the margins, glabrous, 4-lobed; lobes 1–1.5 mm long, apex rounded and thickened. Corolla hooded, 2-lipped, upper lip 2-lobed, lower lip 3-lobed, ground color white with 3 violet nectar guides per lobe running from the middle part of the tube to near the lobe apices, mostly glabrous except for the outer surface of the hood, which is covered by eglandular short trichomes not extending to the lobes or tube; corolla upper side 5–5.2 mm long, tube 3.5 mm long with the anterior filaments attached at 1.7 mm from corolla base, hood 1.2 × 1 mm (excluding lobes), upper lip 1.5 × 1.5 mm, cleft between upper lobes 0.3 mm depth, lower lip 1.5 × 3 mm, cleft between lower lobes 0.5 mm depth, lobes slightly emarginate to rounded. Androecium didynamous, anthers 0.8 × 0.3 mm, free, clustered and enclosed below the hood, awns 0.2 mm long, slits glabrous. Ovary 1.5 × 1.2 mm, oblong, glabrous; style c. 3 mm long, curved downwards below the hood, quick withered after anthesis; stigma 0.3 mm long, short papillose. Capsules 2.5 × 1.5 mm (immature), oblong-elliptic, glabrous, dark brown, lustrous. Seeds c. 7, 1 × 0.5 mm, ellipsoid.

Distribution. – Endemic to the Chilean Patagonian archipelagos of the Aysén Region. Apart from the locus classicus, the species is known only from the presently recorded locality (Fig. 1). Based on the recent revision of Ortiz et al. (2021), Euphrasia perpusilla is the only species of the genus distributed in the archipelagos of western Patagonia.

Habitat. – Individuals of Euphrasia perpusilla were found growing on hygrophilous, mostly ombrotrophic, and poorly-drained pulvinate herbaceous communities dominated by Donatia fascicularis J.R. Forst. & G. Forst., Astelia pumila (G. Forst.) Gaudich., and Schoenus antarcticus (Hook. f.) Dusén, which are commonly surrounded by the dwarf podocarp Lepidothamnus fonkii Phil. Most of the flora associated with this vegetation are diminutive herbs such as Caltha appendiculata Pers., C. dioneifolia Hook. f., Drosera uniflora Willd., Gaimardia australis Gaudich., Gentianella sp., Oreobolus obtusangulus Gaudich., Microschizaea fistulosa (Labill.) C.F. Reed, Tapeinia pumila (G. Forst.) Baill., and some small repent or procumbent shrubs like Gaultheria antarctica Hook. f., G. pumila (L. f.) D.J. Middleton, and Myrteola nummularia (Poir.) O. Berg. (see Fig. 2A, B). This community occurs patchily among areas of exposed old intrusive rocks (granitoid) deposited mostly during the Early Cretaceous in what is known as the South Patagonian Batholith (Sernageomin, 2002; HervÉ et al., 2007), thickets of Metrosideros stipularis (Hook. & Arn.) Hook. f. (≡ Tepualia stipularis (Hook. & Arn.) Griseb.), and patches of stunted forests of Pilgerodendron uviferum (D. Don) Florin, Nothofagus antarctica (G. Forst.) Oerst., N. betuloides (Mirb.) Oerst., and Podocarpus nubigenus Lindl.

This community, widely distributed in archipelagos and coastal mainland areas with oceanic influence in western Patagonia, conforms the Magellanic Moorland (Godley, 1960) or Tundra Complex (Pisano, 1983), which ranges chiefly from Tres Montes Peninsula and the Gulf of Penas area (Fig. 1) southwards to the end of the Patagonian archipelagos (c. 56°S). North of Tres Montes Peninsula, this community becomes patchy and less common, reaching as north as 38°S in the Nahuelbuta Coastal Range (VillagrÁn, 1988, 2001; RamÍrez et al., 2023).

Conservation status. – After its description in 1858, Euphrasia perpusilla was not recorded again until now. Nevertheless, the distance between the locus classicus and the new locality suggests that E. perpusilla may be distributed across the whole archipelagic area of the Aysén Region (Fig. 1), and probably in the northern part of the Magallanes Region. Western Patagonia in the Aysén Region has been proposed as a transition area between Valdivian and Magellanean provinces (rivas-martÍnez et al., 2011), as well as between the North-Patagonian and Magallanean forests (Arroyo et al., 1997). However, all the archipelagic area of Aysén is classified under the same macrobioclime, ombrotype, termotype, continentality, and bioclime (Luebert & Pliscoff, 2017). Therefore, instead of considering E. perpusilla as an extremely rare or scarce species, its lack of collections is most likely due to its small size (barely emerging from Donatia cushions), annual life cycle, and the difficult access of the region where it grows. Accordingly, the category Data Deficient (DD) is assigned because data are inadequate to determine a threat category (Iucn, 2012).

Notes. – Euphrasia perpusilla was described based on material from: “In insulis Chonos circa 800 pedes supra mare legit orn. Dr. Fr. Fonk” (Philippi, 1858). Francisco Fonck (1830–1912) was a German doctor and naturalist who arrived in Chile in 1854 and visited the Chonos archipelago in 1857 as part of a hydrographic expedition (Philippi, 1914). He was an avid plant collector and collaborator of R.A. Philippi, who published 69 new species based on Fonck's collections (Macaya & Fonck, 2005). Philippi's types from Chilean taxa are in SGO (Stafleu & Cowan, 1983), however, the material concerning E. perpusilla is missing. In this line, MuÑoz-Pizarro (1960) and MuÑozschick (1973) did not provide any information either about the original material. Ortiz et al. (2021) also reported that they were unable to locate the type. A recent consultation with the SGO staff confirmed that there is no original material of the species in SGO (J. Arriagada, pers. comm.). On this basis, the name E. perpusilla is here neotypified.

The morphological description by Philippi (1858) in the protologue, although brief, provides key features allowing the identification of the new collection as Euphrasia perpusilla. The few vegetative and floral measurements given in the protologue are almost identical to those obtained from the recently collected specimens. Moreover, the apically rounded lobes of the calyx (“laciniis calycinis linearibus, apice rotundatis”) is one of the characters that unequivocally separates E. perpusilla from the remaining South American species, which have lobes with acute apex (Ortiz et al., 2021).

According to Barker (1982), Euphrasia perpusilla belongs to sect. Trifidae. However, this classification may be uncertain since it could have only been based on the brief original description and location. Euphrasia perpusilla is morphologically puzzling and so, its taxonomic position is unclear and it should be treated as incertae sedis until phylogenetic evidence is analyzed with sufficient and robust sampling. Euphrasia perpusilla has free and glabrous anthers, which are features only shared with mainland South American species (sect. Trifidae) and E. disperma Hook. f. from New Zealand (Barker, 1982). However, several characters suggest a closer relationship with other Australasian groups.

The hood of the corolla's upper lip is lacking in sect. Trifidae (Ortiz et al., 2021), however, is a conspicuous feature of Euphrasia perpusilla as in most of the New Guinean species (Van Royen, 1972, 1983), and many others from New Zealand and Australia (Barker, 1982). The stigma in sect. Trifidae is obscurely bilobed with the upper lobe reduced, appearing almost capitate (Ortiz et al., 2021). In E. perpusilla the stigma morphology conforms to what Van Royen (1983) described for the species from New Guinea: “stigma obliquely and unequally 2-lipped”, such as he illustrated for E. scutellarioides Wernham and E. callosa Pennell. In sect. Trifidae, the leaves are trilobed (only in E. adenonota I.M. Johnst.), trisected, or triparted (Ortiz et al., 2021), with deep incisions separating the leaf divisions which are more or less of similar size, leaving a reduced blade area (i.e. the part of leaf or bract excluding the teeth and, if present, the attenuate part of the base, sensu Barker, 1982). In contrast, Euphrasia perpusilla has leaves varying from 3 to 5-lobed, with the basal lobes inconspicuous or significantly smaller than the others, and shallow incisions, leaving a large blade area (Fig. 3A, B). In E. perpusilla, like most of the New Guinea species, the lobes are unequal in size, with an apical median rounded lobe considerably wider than the lateral ones, which decreases in size towards the leaf base. Additionally, in E. perpusilla the lobes are cucullate (Fig. 3A, B), a morphological feature only known from most of the New Guinean species (Van Royen, 1972, 1983), which Barker (1982) described as “oddly hooded”. The leaves of E. adenonota seem also to be slightly cucullate (see fig. 4B in Ortiz et al., 2021), but several other morphological features, like its almost actinomorphic corolla, point to rule out a closer relationship between it and E. perpusilla.

From a phytogeographic point of view, similar cushion bog communities to the ones where Euphrasia perpusilla thrives are those dominated by Donatia novae-zelandiae Hook. f. from New Zealand and Tasmania (Cockayne, 1921; Kirkpatrick, 1977, 1997; Gibson & Kirkpatrick, 1985). Additionally, phylogenetic relationships of species integrating the communities associated with E. perpusilla show a pattern of transpacific affinities with Australasia (e.g. Astelia [Birch et al., 2012], Donatia J.R. Forst. & G. Forst. [Wagstaff & Wege, 2002; Carolin, 2007], Drosera L. [Rivadavia et al., 2003], Gaimardia Gaudich. [Cooke, 1998; Ford, 2014], Lepidothamnus Phil. [Klaus & Matzke, 2020], Metrosideros Banks ex Gaertn. [Pillon et al., 2015], and the Phyllachne J.R. Forst. – Forstera L. f. complex [Wagstaff & Wege, 2002; Carolin, 2007]). Some authors have proposed that early Gondwanean connections explain such a pattern (Du Rietz, 1960; Barker, 1982, 1986; Heads, 2014).

Finally, considering the conservative taxonomic approach proposed by Ortiz et al. (2021), and adding Euphrasia achibuenoensis and E. perpusilla, Euphrasia in South America includes nine endemic species plus one adventitious from Eurasia (see updated key below). Based on morphological and phytogeographic evidence, the closest relationships of E. perpusilla seem to lie towards Australasia rather than mainland South America.