Caldasia

Colombian lucanid records from the literature

According to the literature, there are 19 species of Lucanidae recorded from Colombia, grouped in five genera, three tribes, and two subfamilies (Table 1). Eight of those species are considered Colombian endemics. Most species (17) belong to the subfamily Lucaninae. With twelve species, the genus Sphaenognathus is the most diverse lucanid genus in the country; the remainder genera are represented by one or two species.

Descriptions of lucanid species recorded from Colombia are scattered through time and by author: (Parry 1872, 1874, 1875) described four species; (Boileau 1904, 1911) and (Buquet 1838, 1840, 1843), each described three species. Most of the type material is deposited at the Muséum national d'Histoire naturelle (MNHN) in Paris, France, followed by The Natural History Museum (NHMUK) in London, United Kingdom. Most species were described between 1911 and 1938. Only one recent taxonomic revision (Cáceres and Grossi 2023) has included Colombian material. During the last decade two new species of Lucanidae have been described from the Colombian Andes (Psilodon paschoali Pardo-Locarno and Ríos-Málaver, 2011 and Aegognathus dulima Cáceres, Ríos-Málaver and Grossi, 2019).

As for distributions, according to the literature, Colombian lucanids are more diverse in the Andean region (Antioquia, Boyacá, Caldas, Risaralda, Norte de Santander, Santander, Tolima), with some representatives in the Caribbean (Cesar, Magdalena) and Pacific (Cauca, Chocó, Valle del Cauca), and one species from the Orinoco region of the country (Meta) (Fig. 2). No specific localities are known for one species (Aegognathus leuthneri van de Poll, 1886).

Figura 1: Number of lucanid taxa per country across the Americas.

Colombian lucanid records from online platforms

We recovered 140 records from iNaturalist (Supplementary Material 1; Fig. 2), from which 120 were identified to species (Cáceres and Ríos-Málaver verified the identifications). The records correspond to fourteen species, from which 122 specimens belong to the genus Sphaenognathus, with Sphaenognathus feisthamelii (Guérin-Méneville, 1838) representing the highest number of records (46) and the broadest distributional range (Antioquia, Boyacá, Cundinamarca, Norte de Santander, Risaralda, Santander, and Valle del Cauca), followed by Sphaenognathus bellicosus Boileau, 1904 (26 records; Cesar, Magdalena).

Records from GBIF were very heterogeneous in the information provided. Out of the 348 downloaded records (GBIF.org), 232 corresponded to preserved specimens identified at various taxonomic categories. Three species (one record each: Lucanus capreolus (Linnaeus, 1763), Odontolabis bellicosa (Castelnau, 1840), and Platycerus scarabeoides -which is not an existing name) were excluded from the list due to evident errors or inaccuracies in the data: Lucanus species have Neartic and Paleartic distributions; the specimen identified as L. capreolus is recorded from Soacha (Cundinamarca), but it is likely a misidentification. The species O. bellicosa is not currently recognized as a valid species, the valid name is Odontolabis dalmani (Hope, 1845) and its distribution is restricted to Indonesia and Malaysia; the specimen in question is housed at the Museo Entomológico Francisco Luis Gallego in Medellín, but has no locality data; it is likely a misidentification.

Figura 2: Distribution map of the Colombian species of stag beetles. Note that O. pulverosus and A. leuthneri do not have accurate distribution data available.

Figura 3: Morphological features of male Lucanidae. a. Antennae of Psilodon aequinoctiale, arrow showing pedicel insertion, non-geniculate (scale bar 1 mm); b. Antennae of Aegognathus leuthneri, arrow showing pedicel insertion, geniculate (scale bar 1 mm); c. Ocular canthus complete of Sphaenognathus nobilis (scale bar 1mm); d. Ocular canthus incomplete of Aegognathus dulima (scale bar 1 mm); e. Elytra of Cantharolethrus luxerii luxerii, surface without longitudinal costae (scale bar 10 mm); f. Elytra of Onorelucanus pulverosus, surface with few longitudinal costae (scale bar 20 mm) Photo courtesy P. Grossi.

Figura 4: Morphological features of Lucanidae. a. Male pronotum of Onorelucanus pulverosus, arrows showing strongly convex lateral margins; b. Male pronotum of Aegognathus dulima, arrows showing nearly straight to slightly convex lateral margins; c. Female antennal club of Aegognathus leuthneri, with three lamellae; d. Female antennal club of Sphaenognathus nobilis, with five lamellae; e. Female head of Cantharolethrus luxerii luxerii, arrow showing the strongly excavated vertex; f. Female head of A. leuthneri, arrow showing the non-excavated vertex. Scale bars 1 mm.

Tabla 1: Species of Lucanidae recorded from Colombia. Species marked with an asterisk (*) are considered Colombian endemic. For additional details on localities see Cáceres et al. (2022). All the original descriptions are cited in Supplementary Material 2.

We recovered twelve species of three genera, recorded from Amazonas, Antioquia, Atlántico, Boyacá, Caquetá, Cauca, Cundinamarca, Huila, Magdalena, Norte de Santander, Risaralda, and Valle del Cauca. Cantharolethrus luxerii (Buquet, 1843) was the most widespread species and with the highest number of records (Amazonas, Boyacá, Cundinamarca, Huila, and Valle del Cauca; 71 records). For four of the identified species (Psilodon aequinoctiale (Buquet, 1840) - one record, Sphaenognathus albofuscus Blanchard, 1842 - a junior synonym of S. prionoides Buquet, 1838 - three records, S. rotundatus Lacroix, 1987 - one record, and S. taschenbergi Parry, 1874 - one record), no specific localities were provided. Specimens of S. albofuscus and S. taschenbergi belong to the NHMUK and are likely old specimens, as evidenced by the scarceness of the available information. It is likely that such localities have been recorded as Colombia for old specimens labeled as "New Granada", which nonetheless, encompassed parts of what is nowadays Brazil, Ecuador, Guyana, Peru, and Venezuela.

Colombia has representation of 6.4 % of the genera and 5.5 % of the lucanid species recorded for the Americas (Fig. 1). Considering only South America, Colombia has 8.1 % of the genera and 6.6 % of the described species.

Figura 5: Elytral surface of lucanid females. a. Onorelucanus pulverosus, with moderate to large and dense punctation; b. Aegognathus leuthneri, with coarse and contiguous punctation. (Scale bars 1 mm).

Identification keys to the genera of Colombian Lucanidae

Identification key to the males of lucanid genera present in Colombia

1. Antennae non-geniculate (pedicel inserted on the apex of the antennal scape, at 180°; Fig. 3a)... Syndesinae, Syndesini, Psilodon

1'. Antennae geniculate (pedicel inserted on the anterodorsal face of the apical region of the antennal scape at an oblique angle, forming a 90° angle with scape; Fig. 3b)... 2

2. Ocular canthus entire, dividing eyes into dorsal and ventral faces (Fig. 3c)... Chiasognathini, Sphaenognathus

2'. Ocular canthus not entirely dividing eyes, covering anterior third or half of eyes (Fig. 3d)... Sclerostomini... 3

3. Elytral costae absent; body entirely black (Fig. 3e)... Cantharolethrus

3'. Elytra with few to several longitudinal costae; body color, variable, often with reddish and bluish reflections, somewhat black on head (Fig. 3f)... 4

4. Lateral margins of pronotum strongly convex (Fig. 4a)... Onorelucanus

4'. Lateral margins of pronotum nearly straight, abruptly narrowed at anterior and posterior angles (Fig. 4b)... Aegognathus

Identification key to the females of lucanid genera present in Colombia

1. Antennal club with three lamellae (Fig. 4c)... Sclerostomini... 2

1'. Antennal club with five or more lamellae (Fig. 4d)... Chiasognathini, Sphaenognathus

2. Head vertex with a strongly excavated spot (Fig. 4e)... Cantharolethrus

2'. Head vertex without excavations, flattened to slightly convex (Fig. 4f)... 3

3. Dorsal surface of body with dense and moderate to large punctation, somewhat contiguous along lateral portion of elytra (Fig. 5a)... Onorelucanus

3'. Dorsal surface of body with coarse, contiguous punctation (Fig. 5b)... Aegognathus

Colombian stag beetles in the Neotropical context

The known diversity of stag beetles in Colombia can be considered low, especially when compared with Peru, which has more than double the number of species in a slightly larger area (1 139 vs. 1 285 million km², respectively) or Ecuador (283 560 km²), which with about one-fourth of the territory has a slightly larger number of species. Considering the known Andean affinities of some lucanid taxa, these differences can be attributed to revisionary studies involving new species from Ecuador (e.g., Bartolozzi et al. 1992) and Peru (e.g., Arnaud and Bomans 2007), but lacking in Colombia.

Figura 6: Some representative species of the Lucanidae fauna of Colombia, observed in their natural habitats. a. Psilodon paschoali ♂, Cerro de la Uchata, Serranía de los Yariguíes, Santander, 2200 m.a.s.l.; b. Cantharolethrus luxerii ♂, Calima, Darien, Valle del Cauca, 1300 m.a.s.l.; c. C. luxerii ♀, PNN Las Orquídeas, Antioquia, 1300 m.a.s.l.; d. S. signatus ♂, La Gruta, Villa María, Caldas, 3300 m.a.s.l.; e. S. signatus (♂ major) Reserva Forestal Protectora, Bosques de la CHEC, Manizales, 2500 m.a.s.l.; f. S. spinifer ♂, Farallones de Cali, Valle del Cauca 1700 m.a.s.l.; g. S. bordoni ♀, Carcasí, Santander 3200 m.a.s.l.; h. S. nobilis ♂, Serranía del Perijá, Colombia, 3000 m.a.s.l.; i. S. prionoides ♀, Carcasí, Santander 3200 m.a.s.l.; j. S. bellicosus ♂, Filo de San Lorenzo, Sierra Nevada de Santa Marta, Magdalena 2500 m.a.s.l.; k. S. bellicosus ♀, Filo de San Lorenzo, Sierra Nevada de Santa Marta, Magdalena 2500 m; l. S. feisthamelii (♂ major), Pamplona, Norte de Santander, 2600 m.a.s.l.; m. S. feisthamelii ♀, Galán, Santander Serranía de los Yariguíes, 2700 m.a.s.l.; n. S. feisthamelii ♀ Arcabuco, Boyacá 2300 m.a.s.l.; o. S. armatus ♀ Duitama, Boyacá, 3000 m.a.s.l.

Photos by Indiana Cristo

On the other hand, Brazil is the country with the highest number of described lucanid taxa across the Americas, with 76 species classified in fourteen genera, of which eleven are endemic. Most Brazilian lucanids are restricted to the eastern highlands of the Atlantic Forest and to a lesser extent, distributed across the Amazonian biome (Vulcano and Pereira 1961, Grossi and Aguiar 2014). There are several factors contributing to the large number of species known from Brazil: (1) a large territory in a tropical region; (2) the existence of a monograph treating the Brazilian fauna of stag beetles (Luederwaldt 1935), that served as the baseline for recent studies; (3) the presence of a highly trained specialist, Paschoal C. Grossi, who has been contributing to Lucanid knowledge since 2003, and has not only been focused on Brazilian diversity, but also has made significant contributions to the taxonomy of Andean Stag Beetles (Grossi and Paulsen 2009, Grossi 2011, Grossi and Bartolozzi 2011). These key factors have resulted in the existence of an updated catalog for Brazil (Grossi 2023). With this kind of information, Brazilian researchers brought attention to the conservation needs of these beetles, considering vulnerable all seven species of the endemic genus Altitatiayus Weinreich, 1960, now included in the list of species threatened by extinction (Ministério do Meio Ambiente 2022). These and Chiasognathus granti Stephens, 1831, a rare and vulnerable species from Chile (Vergara and Jerez 2009), are the only protected lucanid species in South America.

The local context of Colombian lucanids

There is evidence that our knowledge about biodiversity in Colombia is biased towards increased data and studies in the Andean region (Arbeláez-C 2013). In the case of lucanids, this bias is actually a reflection of the ecological habits of these beetles. Colombian lucanids are mostly restricted to high elevation ecosystems along the Andes, in an altitudinal range between 1300 and 3900 meters above sea level (m.a.s.l.). Most of the species are associated with montane forests and paramos, which are ecosystems characterized by their high biodiversity, high levels of endemism (Young and Leon 2000, Etter and van Wyngaarden 2000, Larsen et al. 2011, Madriñán et al. 2013, Cuesta et al. 2017, Hazzi et al. 2018), and high conservation value (Bush et al. 2007, Russi et al. 2013).

Besides distributional data for Colombian lucanids we found information about their seasonality (Ríos and Salazar 2005, Salazar et al. 2010), which along with field observations (by ICRM and JSDC), suggest that stag beetle populations are more frequently observed during higher rainfall peaks in the Andean region (April--May and October--November), which is consistent with the close relationship between different beetle taxa and humid seasons (Ortega-E et al. 2019, García et al. 2021).

Observations from iNaturalist represent the most recent records for Psilodon, Cantharolethrus, and Sphaenognathus species, as well as additional phenological information. In addition, there are records of rare and little-known species that allow for a better understanding of their ecological habits. This shows that community science is a powerful tool to assist formal research teams in the absence of enough available material in national collections and scarce fieldwork.

On the other hand, the armed conflict in Colombia has generated isolation in regions of high interest for their biodiversity (Arbeláez-C 2013). The lack of guaranteed safety for researchers in the field has restricted opportunities to explore and study Colombian Lucanidae in high mountain landscapes of high interest, in areas of the departments of Antioquia, Cauca, Cesar, Córdoba, Chocó, Huila, Magdalena, Valle del Cauca, and Norte de Santander.

Taxonomic studies involving Colombian stag beetles are lacking, which makes it difficult to conduct ecological, populational, and evolutionary studies, as well as to assess conservation status. This situation is compounded by the absence of funding for basic research, the lack of experienced taxonomists, and the limited access to type material, which is for the most part, deposited in European collections (Girón et al. 2021). Even when this scenario is not promising, this work represents the first effort to summarize information about this charismatic and yet neglected group of beetles in Colombia.

Towards conservation assessments for Colombian stag beetles

The constant transformation of highland landscapes, where the greatest richness and endemism of these rare beetles is concentrated in Colombia, increases their extinction risk (Ríos and Salazar 2005). Human activities including deforestation, agriculture, illegal mining, and hydropower production (Huang 2018, Bax and Francesconi 2018, Bax et al. 2019) are key causes of habitat loss that can have detrimental effects on stag beetle populations across the Andes. There is at least one Colombian endemic lucanid species (Sphaenognathus mandibularis Boileau, 1911) that is only known from its original description and has apparently never been collected again. The natural Andean forest areas in the vicinity of the type locality (Medellín, Antioquia), have undergone intense transformation by human activities in the last century, especially urbanization and forest monocultures, which has possibly negatively impacted the populations of this extremely rare species.

Neotropical lucanids are among the most desired groups of insects by collectors worldwide (Goka et al. 2004; Crespin and Barahona-S 2022). Illegal trade of species constitutes a latent threat (New 2010) to Colombian stag beetles, especially considering the rarity of their populations. This is especially evident in the relatively large series of specimens that are present in foreign (including private) collections.

For Lucanidae, the combination of widespread rarity of the species, the lack of data about population dynamics, the significant gaps in ecological knowledge, and the low number of regional specialists, hinder the development of conservation strategies for this beetle family. Given the tight ecological association between lucanids and fragile montane habitats (see Fig. 2), the conservation status of Colombian lucanids must be evaluated urgently. This contribution constitutes a baseline for the analysis of geographic distributions, habitat specificity, and threats that are needed (e.g., Fallon et al. 2021) to propose Colombian lucanids as species in need of conservation efforts. We envision the stag beetles of Colombia as objects of conservation efforts that can promote evaluations for other beetles, other insects, and invertebrates in general.