A new species of concealer moths (Oecophoridae), Denisia cryptica sp. nov., is described from specimens collected in the south-western Alps (Italy, France). It differs from similar congeneric taxa of the Denisia stipella species-group by a combined pattern of colour and markings of the forewing upperside, the colour of the head, particularly the yellow second segment of the labial palpi, and by highly divergent DNA barcode (cytochrome c-oxidase subunit 1) sequences. Male and female genitalia are like several other species, with only subtle diagnostic characters. Adult and partially genitalia of D. cryptica sp. nov. and the closest European species are shown for comparison. Finally, a complete checklist of European species of Denisia is added.

Cottian Alps, cryptic morphology, endemism, France, Italy, Oecophorinae

Denisia is one of the species-rich genera in Europe within the family Oecophoridae, which is represented here by 139 species (Lepiforum 2024). 23 species of Denisia have been recorded in Europe (Lepiforum 2024). Remarkably, four of these species were only discovered in the 21^st century (Huemer 2001; Lvovsky 2007; Corley 2014; Nel and Varenne 2019), although one of them, Denisia lutea Varenne & Nel, 2019, has been incorrectly synonymized with the North African Denisia curlettii Lvovsky & Koster, 1996 (Leraut 2023; Nel and Varenne 2024). No additional congeneric species are currently known from Asia. However, two species are recorded from North America, viz. Denisia yukonella Lvovsky, 2007 and Denisia haydenella (Chambers, 1877), with the former now considered as junior synonym of Brymblia quadrimaculella (Chambers, 1975) (Pohl and Landry 2023). This synonymization reflects the general lack of a phylogenetic analysis of the subfamily Oecophorinae. Consequently, the generic delimitation of Denisia and other genera requires further investigation, particularly through extensive molecular analyses.

Only a few species like Denisia stipella (Linnaeus, 1758) and Denisia similella (Hübner, 1796) are widely distributed across the continent, especially in the temperate zones, while the vast majority have more localized ranges. Particularly, the various major mountain systems in Europe such as the Pyrenees, Alps, or Caucasus, as well as large Mediterranean islands, are partly inhabited by regional endemism. However, recently studied molecular data suggest a significantly underestimated species diversity, especially among species with allopatric distribution patterns (Huemer and Mutanen 2015; Zlatkov and Huemer 2017; Huemer 2022; Huemer and Wieser 2023).

The preimaginal life habits of Denisia species are insufficiently explored and often completely unknown. Tokár et al. (2005) mainly cite the bark of decaying or dead wood, rarely also lichens growing on trees, as larval substrates for the Central European fauna. However, there appear to be two trophic adaptation strategies: a large group of species, as far documented, lives on dead wood, while the other, as primarily demonstrated by Schmid (2019) for D. rhaetica (Frey, 1856), feeds on lichens growing on rocks. Typical megabiomes of Denisia species thus encompass both forest habitats and rocky environments, extending into the alpine zone.

In the course of a comprehensive survey of Lepidoptera in the nature parks of the Cottian Alps (northwestern Italy) (Huemer and Wieser 2023), a new and previously unknown species of the genus Denisia has now been discovered, thanks to rigorous molecular identification controls using DNA barcoding.

In addition, a comprehensive checklist of European Denisia is provided in this paper.

A total of 224 specimens of phenotypically similar Denisia have been examined morphologically: 4 D. cryptica sp. nov., 22 D. nubilosella, 133 D. stipella, 37 D. similella, 23 D. fuscicapitella (all Central Europe), and 1 D. subaquilea (Spain), 2 D. obscurella (Finland), 2 D. luticiliella (Russia). External and internal morphology of North American D. haydenella is based on Hodges (1974) and BOLD, with supplementing comments and unpublished figures from Landry (in litt.). Further externally very distinct species were only considered for genetic analysis. The material is preserved in the Research Collection of Tiroler Landesmuseum Ferdinandeum (Austria). Species identification is based on the phenotypic characteristics of the adults and partly confirmed by dissections and DNA barcoding.

Tissue samples (a single hind leg) from three D. cryptica sp. nov. were prepared according to prescribed standards to obtain DNA barcode sequences of an optimally 658 bp segment of the mitochondrial COI gene (cytochrome c oxidase subunit 1). The material was successfully processed at the Canadian Centre for DNA Barcoding (CCDB, Biodiversity Institute of Ontario, University of Guelph) using the standard high-throughput protocol described in deWaard et al. (2008). In addition, 155 public and private barcode sequences of 19 species of Denisia in the Barcode of Life Data Systems (BOLD; Ratnasingham and Hebert 2007; Ratnasingham 2018) were used for analysis. All barcode sequences, except for two shorter sequences of D. pyrenaica, range between 560 and 658 bp. Further details including complete voucher data and images can be accessed in the public dataset DS-DENISIA1 “Denisia sp.n. - Alps” dx.doi.org/10.5883/DS-DENISIA1 in the Barcode of Life Data Systems BOLD (Ratnasingham and Hebert 2007).

All sequences were assigned to Barcode Index Numbers (BIN), algorithm-based operational taxonomic units that provide an accurate proxy for the true species. BINs were automatically calculated for records in BOLD that comply with the DNA Barcode standard (Ratnasingham and Hebert 2013).

Degrees of intra- and interspecific variation of DNA barcode fragments were calculated using the Kimura two-parameter model on the platform of BOLD systems v. 4.0. (https://boldsystems.org). A Neighbor-Joining tree was constructed using the Kimura two-parameter model in MEGA7 (Kumar et al. 2016).

Photographs of adults were taken with an Olympus OM-D Mark III camera and a 60 mm macro lens, genitalia photographs with a Zeiss Axiolab 5 microscope, mounted with an Olympus OM-D Mark III camera. 60 to 90 stacked photographs were edited using Helicon Focus 4.8 and Adobe Photoshop 6.0.

A linguistic review was conducted on ChatGPT.

Abbreviations. TLMF = Tiroler Landesmuseum Ferdinandeum, Innsbruck, Austria.

The discovery of a potentially local endemic species in the European Alps may come as a surprise at first glance. However, the Southern Alps exhibit a particularly high degree of endemism (Huemer 1998). The area of the Cottian Alps has long been recognized as a hotspot for endemic Lepidoptera, and even in the 21^st century, several new species have been described from there (Baldizzone and Gaedike 2004; Gianti 2005; Huemer and Hebert 2011; Nel 2012; Huemer and Mutanen 2015; Huemer et al. 2020). The systematic application of molecular methods in identifying extensive newly collected material, however, suggests an astonishingly large number of additional, previously overlooked cryptic species (Huemer and Wieser 2023).

As a fundamental issue in the delineation of Denisia species, the widespread cryptic morphology of many representatives of the genus has proven to be a challenge. Similarities in external appearance occur in numerous species pairs or groups. However, even the delineation using genital morphological characteristics often reaches its limits in this genus, meaning that the specifically evaluated genital morphology is frequently based on subtle features. Here, a characterization of species using molecular data, especially DNA barcode sequences, appears to lead to more indisputable results. All analyzed species of Denisia exhibit significant interspecific divergences on the order of approximately 4–9%. This extent of genetic divergence appears to be highly representative for the genus due to the large number of sequenced taxa. Out of the globally described 24 species, barcode sequences are available for 19 species. Only the species pair D. pyrenaica and D. graslinella shows, based on the few known sequences, an overlap in the DNA barcode, which may, however, possibly be due to a previously overlooked synonymy of these two taxa. Conversely, striking intraspecific divergences have also been documented in the genus Denisia, exceeding 5% in D. rhaetica and D. albimaculea. However, initial analyses suggest further overlooked cryptic diversity, although taxonomic revisions in these species groups are still pending.

The newly described D. cryptica sp. nov. fits into the overall picture of a genetically strongly divergent species, which, however, is difficult to differentiate from other congeners both phenotypically and in genitalia structures. Most helpful and effective are especially complexes of features from color and pattern of the forewing upper surface combined with head coloration and colour of the labial palps and antennae.

The author is most grateful to Paul Hebert and his team at the Centre for Biodiversity Genomics (Guelph, Canada), whose sequencing support and the BOLD informatics was enabled by funding from the Canada Foundation for Innovation, by Genome Canada through Ontario Genomics, and by the Tri-Council’s New Frontiers in Research Fund. Collecting permits were kindly issued by the current and former director of Alpi Cozie Nature Parcs, Luca Marello and Michele Ottino. Andreas Eckelt (TLMF) is acknowledged for technical support.