Synopsis of the Colombian Stag Beetles: A baseline for conservation assessments

Stag beetles, or Lucanidae (Insecta: Coleoptera: Scarabaeoidea), are among the most charismatic groups of scarab beetles. However, their ecology and natural history are largely unknown, partly due to their rarity in the field and in biological collections. This contribution summarizes the status of knowledge of the Colombian Lucanidae, based for the most part in bibliographic research and personal observations from fieldwork and biological collections in Colombia and Brazil. Bibliographic records are supplemented by data from the Global Biodiversity Information Facility (GBIF), including field observations recorded through the online platform iNaturalist. In the literature, we found 19 species of stag beetles recorded for Colombia, belonging to five genera, three tribes, and two subfamilies. Bibliograph-ic records are concentrated in the Andean region of Colombia, with some records in the Caribbean and Pacific regions. The lowlands of the Amazon and Orinoco regions lack any records for lucanid beetles. The diversity and ecology of stag beetles in Colombia are discussed in the light of current environmental threats. By presenting diagnoses and an identification key to the lucanid genera present in the country, along with known distributional data, and a discussion about their ecology, this contribution constitutes the first step towards proposing Colombian lucanids as species in need of conservation efforts.


INTRODUCTION
Stag beetles (Coleoptera: Lucanidae) are a small family in the superfamily Scarabaeoidea represented by approximately 1500 species in 115 genera, distributed worldwide (Bouchard et al. 2017).According to Holloway (1960Holloway ( , 1968Holloway ( , 1969Holloway ( , 2007)), Lucanidae is composed of four extant subfamilies: Aesalinae MacLeay, 1819; Lampriminae MacLeay, 1819; Syndesinae MacLeay, 1819; and Lucaninae Latreille, 1804, which is the most diverse, representing around 90 % of the described species.Traditionally, Lucanidae has attracted the attention of the scientific community and non-scientific public, and even in the absence of identification keys, it is possible to identify them at least to supraspecific levels.
Lucanid beetles can be recognized by the following combination of characters: size 3-120 mm, body flattened to weakly convex; antennae usually with ten antennomeres, with tomentose and unopposable lamellae; labrum usually continuous with clypeus, which is fused with frons; legs serrate; protibiae with one apical spur; meso-and metatibiae with two spurs (Ratcliffe 2002).There is evident sexual dimorphism in most species of the family (somewhat reduced in Aesalinae), where males present greatly enlarged and symmetric mandibles, whereas females show reduced and frequently asymmetric mandibles (compare fig. 3B, male, with 4f, female; Kim and Farrel 2015).There are also other differences such as stronger body punctation and reduced antennal club in females.The development of male mandibles is allometric, with a significant reduction in minor males, producing a close resemblance to females, characterized by not only the reduction in size but also a reduction in body vestiture, sometimes making it difficult to distinguish both sexes (Kawano 2000).
Most taxa are extremely under-represented in collections, being more commonly found in private collections where access is restricted, which makes it difficult for taxonomists to study them.
This may be one of the reasons why lucanid classification is highly inconsistent, especially at the suprageneric level (Smith 2006, Holloway 2007).Due to a lack of taxonomic revisions and available identification keys, the most common way to identify them is through images provided in books such as Fujita (2010) and Bartolozzi et al. (2017), or updated catalogs like Paulsen (2019).
Besides taxonomic limitations, lucanid beetles are extremely rare in nature, which has made it difficult to conduct studies on ecology and life history of this family.Despite this, it is wellknown that stag beetles are saproxylic, with larvae feeding on dead wood; the females oviposit either directly in decaying wood, at the soil-wood interface beneath logs, or in the soil (Huang 2018).Their role as decomposers and ecosystem engineers are key for maintaining forest ecological dynamics (Fierro andVergara 2019, Crespin andBarahona-S 2022).
According to Paulsen (2019), stag beetles from the Americas represent around 15 % of the total described species, with representatives of all four subfamilies: Aesalinae (four genera, 18 species), Lampriminae (one genus, one species), Lucaninae (32 genera, 215 species), and Syndesinae (three genera, twelve species).In the Neotropical region, lucanids can be found in most countries, with no records from Belize, Suriname, and the Caribbean Islands (Fig. 1), except for an amber fossil from the Dominican Republic described by Woodruff (2009).
In South America most species have been described from Brazil, Ecuador, and Peru.Most species are associated with high elevation ecosystems of high conservation value, as the majority of the known localities are distributed across some of the most important biodiversity hotspots, such as the Tropical Andes and the Brazilian Atlantic Forest (Myers 2000).However, only Chiasognathus grantii Stephens, 1831 from Chile (Vergara and Jerez 2009), and species of the Brazilian endemic genus Altitatiayus Weinreich, 1960 (Ministério do Meio Ambiente 2022) have been included in national conservation strategies.
For the specific case of Colombia, current knowledge is scarce.Only 19 species in five genera are known for the country: Sphaenognathus Buquet, 1838, Aegognathus Leuthner 1883, Cantharolethrus Thomson, 1862, Onorelucanus Bartolozzi and Bomans, 1989, and Psilodon Perty, 1830.Some lucanid species are only known from their original descriptions, with no known recent material available for study.Lucanids are underrepresented in Colombian scientific collections; in some cases, private collections have more and rare material for study, but are essentially inaccessible for research.With no catalogs, identification keys, accurate distributional data, or scientific researchers focused on the taxon, the need for taxonomic, evolutionary, and conservation studies regarding Colombian stag beetles is evident.This work is the first summarized contribution to the knowledge of Colombian Lucanidae, providing basic but fundamental information that serves as the baseline for ecological studies, and the first step towards evaluating extinction risks for Colombian lucanid beetles.

MATERIALS AND METHODS
The list of species of Lucanidae was initially extracted from Paulsen's online annotated checklist of the Lucanidae of the Americas (Paulsen 2019).Additional references for each taxon were revised to extract locality information in Colombia, including the original description for each species, available catalogs, and taxonomic or faunistic revisions for the world and the region.
The list was formatted as a Darwin Core Checklist available through the Global Biodiversity Information Facility -GBIF (Cáceres et al. 2022).
The core checklist dataset includes the extensions Reference, Types and Specimen, and Species Profile, to accommodate the following information: (1) valid/accepted scientific name; (2) author and year of description; (3) relevant bibliographic resources, including original description, checklists, and catalogs; (4) Colombian localities where the species has been documented; (5) information on type material when it was readily available from publications; (6) origin (native vs. introduced); ( 7) endemism: taxa are considered Colombian endemics if no records from other countries were found in the published literature; (5) general ecological habit of each species.
In addition, we downloaded all the records for observation data for Lucanidae from Colombia from iNaturalist (up to November 4, 2022; Supplementary Material 1).We also downloaded data from GBIF by searching occurrence data by 'Country or area' Colombia and 'Scientific name' Lucanidae (GBIF.org2022), which includes observation data along with information on preserved specimens from collections.We assumed that identifications for preserved specimens from GBIF are correct.
Using these data, we constructed a distribution map including the Colombian species of stag beetles (Fig. 2).To build the map, we used QGis v.3.10, using as a base layer a shapefile for South America (provided by the Environmental Systems Research Institute-ESRI), available at http://tapiquen-sig.jimdo.com.We included an additional layer containing a Digital Elevation Model for South America, published by the Center for Earth Resources Observations and Science, available at http://databasin.org/datasets/d8b7e23f724d46c99db1421623fd1b4f.c.

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.
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. 10 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.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)  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.

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 onefourth 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.
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 andPereira 1961, Grossi andAguiar 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 andSalazar 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.

ACKNOWLEDGMENTS
Our major gratitude is to †German E. Amat García, a Colombian coleopterist that was a pioneer in the study of many groups of Colombian insects, especially beetles.On different occasions, he expressed to some of the authors his interest in the study of the family Lucanidae in the country, but unfortunately, he passed away before we could consolidate an idea.Therefore, we dedicate this manuscript to his legacy in science, to his efforts for the study of insects in Colombia, and to his passion and dedication to train the next generation of researchers who will continue what he started.We also want to thank Professor Paschoal C. Grossi from the "Coleção Entomológica da Universidade Federal Rural de Pernambuco" (CERPE) for allowing us to use some of his photos and accessing to the entomological material that illustrates our identification key.We are grateful to the Instituto Alexander von Humboldt for facilitating participation in fieldwork that has allowed ICRM to observe more of the ecology and phenology of these fascinating beetles.
The Grupo Coleoptera de Colombia (https://sites.google.com/view/coleopcol/inicio),with its effort to generate beetle species lists for the country, brought us together to produce this manuscript.
, 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).
-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.

Figure 1 .
Figure 1.Number of lucanid taxa per country across the Americas.

Figure 2 .
Figure 2. Distribution map of the Colombian species of stag beetles.Note that O. pulverosus and

Figure. 6 .
Figure. 6.Some representative species of the Lucanidae fauna of Colombia, observed in their

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