Eulithinus analis ( Rambur, 1838 )

Puerta-Rodríguez, Leticia, Jurado-Angulo, Pilar, Jiménez-Ruiz, Yolanda, Rosas-Ramos, Natalia & García-París, Mario, 2024, Systematics of the Sierra Nevada endemic earwig: Eulithinus analis (Forficulidae, Dermaptera), European Journal of Taxonomy 935 (1), pp. 137-165 : 156-158

Eulithinus analis ( Rambur, 1838)

Forficula analis Rambur, 1838: 10 . Terra typica: “… sur les montagnes de la Sierra Nevada… sous les pierres”. Type specimen at the Natural History Museum (London, UK) ( Steinmann 1989).

Forficula brevis Rambur, 1838: 9 . Terra typica: “sous les pierres, dans les montagnes de la Sierra-Nevada”. Type placement unknown ( Steinmann 1989). Syn. nov.

Chelidura analis var. macrolabia Dubrony, 1878: 436 (unavailable name).

Chelidura analis var. cyclolabia Dubrony, 1878: 436 (unavailable name).

Pseudochelidura montana Steinmann, 1981: 189 . Terra typica: “ Spain, Sierra Nevada, 2700 m ”. Holotype at the Hungarian Natural History Museum (Budapest, Hungary) and paratypes at Zoologiske Museum ( Copenhagen , Denmark). Syn. nov.

Eulithinus hispanicus Steinmann, 1984: 202 . Terra typica: “ Spain, Sierra Nevada, Réf. Universitario, 2600 m ”. Holotype at the Museo Civico di Storia Naturale (Verona, Italy) and paratypes at the Hungarian Natural History Museum (Budapest, Hungary) ( Steinmann 1989). Synonymy of E. hispanicus Steinmann, 1984 , with E. montanus proposed by Steinmann (1989).

Chelidura analis – Dubrony 1878: 434.

Pseudochelidura analis – Burr 1908: 11.

Lithinus analis – Burr 1909: 327.

Eulithinus analis – Hincks 1935: 276.

Eulithinus montanus – Steinmann 1989: 744.

Phylogenetic placement of the Sierra Nevada earwig and comments on the systematics of Forficulidae

The Sierra Nevada earwig shares with the species of Pseudochelidura a similar general morphology, including similar complex patterns of male cerci and pygidial variation and a common general habitus ( Cuesta-Segura et al. 2023). Morphological resemblance between species both of Eulithinus and Pseudochelidura partially agrees with the mitochondrial phylogenetic results, which showed that the Sierra Nevada specimens are deeply nested within Pseudochelidura and sister to the Pyrenean P. sinuata ( Fig. 7 ). However, we are well aware of the problems of using only mitochondrial DNA data for taxonomic purposes ( Sainz-Escudero et al. 2021), because organismic evolution is nuclear and therefore mtDNA can only be used as a proxy when no nuclear evidence suggest otherwise ( Moritz et al. 1987; Rissler et al. 2006; Singhal & Moritz 2013), because mtDNA introgression is very common across species with postzygotic isolation mechanisms ( Shimizu & Ueshima 2000; Alves et al. 2003; Babik et al. 2005; Barbanera et al. 2009; Zakharov et al. 2009; Nunes et al. 2010; Mastrantonio et al. 2016), and most importantly, because its haploid nature and maternal inheritance generate very different demographic dynamics with respect to nuclear genes ( Avise et al. 1987, 1988; White et al. 2008). However, it is generally considered that mitochondrial DNA data are particularly useful to depict the biogeographic and past evolutionary history of a taxon (precisely because its maternal inheritance and lack of recombination allow for its long population persistence through time, as shown since the early works of Moritz et al. 1992; García-París et al. 2003). In our case, the cytb data clearly indicates that E. analis and P. sinuata became isolated from a common ancestor much more recently than they did with respect to P. cantabrica . However, the ITS2 phylogeny clearly placed Eulithinus as the sister taxon to the Iberian Pseudochelidura , supporting, or at least not questioning their generic status.

In this situation of morphological similarity, in which, however, the presence of a marked edge in the lateral side of the tegmina of Eulithinus could be clearly interpreted as a generic diagnostic character, and with mtDNA supporting Eulithinus as deeply nested within Pseudochelidura , we cannot make a proper decision on the taxonomic status of Eulithinus . The inclusion in the analyses of the Italian species of Pseudochelidura ( P. galvagnii Vigna Taglianti, 1999 , and P. orsinii ( Gené, 1833)) might shed some additional light on whether Eulithinus should remain as a valid genus or if, alternatively, it should be transferred to Pseudochelidura . Even Steinmann (1979, 1981) while including Sierra Nevada specimens as paratypes of his Pyrenean Pseudochelidura minor (= P. sinuata ) ( Cuesta-Segura et al. 2023), or while describing his Sierra Nevada species Pseudochelidura montana , mixed Eulithinus and Pseudochelidura .

Following the classification criteria used by Burr in 1907, many authors who dealt with the earwigs of Sierra Nevada, included them in the subfamily Forficulinae or Anechurinae . However, Steinmann (1975), followed by Sakai (1992, 1996) and Herrera Mesa (1999) included them in the subfamily Allodahliinae Verhoeff, 1902 . Steinmann (1975) considered that the criterion “border on the sides of the elytra” given by Verhoeff (1902), which also served to describe Allodahlia Verhoeff, 1902 , was a sufficiently important characteristic feature to elevate the group to the rank of subfamily. For this reason, Steinmann included in Allodahliinae all species that possess this character state including Allodahlia and Eulithinus .

Since Eulithinus is close to or nested within Pseudochelidura , it appears that the presence of a marked edge in the humeral angle of Eulithinus tegmina, absent in Pseudochelidura , is a homoplastic trait with respect to the same structure present in Allodahlia . In other words, Allodahlia and Eulithinus would present similar traits in the tegmina by mere convergence and not by presenting a close phylogenetic relationship between them. This inference renders Allodahliinae without a proper diagnostic definition. We consider that the use of subfamilies within Forficulidae should be avoided until a robust phylogenetic analysis of the entire Forficulidae would define properly internal monophyletic subunits (subfamilies) within it.

The close relationship between endemics of Sierra Nevada and Pyrenean taxa is a common theme in the biogeography of European arthropods. Some of the most emblematic insects of Sierra Nevada as Agriades zullichi or Mylabris nevadensis are sister to their Pyrenean, often extended over other European mountain systems, counterparts, and allied species, as Agriades glandon glandon ( von Prunner, 1798) plus A. g. aquilo ( Boisduval, 1832), and Mylabris flexuosa Olivier, 1811 ( Martin et al. 2002; Wiemers et al. 2020). The isolation of the Sierra Nevada and Pyrenean (Western European) taxa have been considered a result of the extinction of the intervening populations during the interglaciar periods. Cold adapted species inhabiting the dry and thermoclimatic areas of southeastern Spain would only survive at high elevations, becoming isolated from all other mountain systems in Western Europe ( Hewitt 2001; Wilson et al. 2005; Ploquin et al. 2013). Our cytb data support that Sierra Nevada populations are related to Pyrenean populations in a well-supported monophyletic group, leaving the Cantabrian populations as sister to them.

Natural history notes and conservation

Eulithinus analis is an endemic taxon to the Sierra Nevada and the adjacent Sierra de Filabres mountain chains in the Penibetic Region of southeastern Spain. The species occurs at high elevations, from 2039 (Pilar de las Yeguas, Puerto de la Ragua) to 3029 m (Laguna de Río Seco; Fig. 10A ) ( Ebner 1959; own data). It is not uncommon in the western area of its range, but it becomes more sporadic towards the east. We have failed to locate the species in the Sierra de Filabres (Almería), where early 20 th century explorers located some specimens (see the historical MNCN Material examined) and where general conditions seem favourable for the species; in any case, the taxonomic status of these populations require further analyses. Eulithinus analis is relatively frequent in open areas within rocky valleys partially covered with grass, and associated with humidity, as small lakes, streams and “borreguiles” (peat bogs) ( Ebner 1959) ( Fig. 10 ), but also at the edge of pine forests (Puerto de la Ragua). Adults are usually found under stones or active at night in humid areas of beneath decaying wooden logs in pine forests during summer months (June to August). Females attend their eggs during this period, sometimes aggregated under the same stone, and often with the remains of dead males nearby ( Fig. 10B ).

During the explorations to localize E. analis in Sierra Nevada and Sierra de Filabres, we often found specimens of Forficula mediterranea González-Miguéns & García-París, 2020 (in González-Miguéns et al. 2020), a member of the F. auricularia species group. The presence of this species at low-mid elevations of Sierra Nevada was expected, but we also observed large densities at high elevations areas in which E. analis typically occurs. In mid-August 2011, we observed more than 300 specimens of F. mediterranea and F. dentata at Puerto de la Ragua, about 50 at Laguna de Aguas Verdes at 3058 m (37°02′53″ N, 3°22′06″ W), and one female at Laguna de Río Seco. The specimen at Laguna de Río Seco ( Fig. 9F ) was located under a stone where females of E. analis were tending egg clutches ( Fig. 10B ), but we did not observe any interaction between them. At Laguna de Aguas Verdes we did not find a single specimen of E. analis , while at Puerto de la Ragua, F. mediterranea clearly dominated, but E. analis was not uncommon. Species of the F. auricularia complex appear in company of species of Pseudochelidura in the Cantabrian Mountains ( Cuesta-Segura et al. 2023), but these limited observations were not designed to identify patterns of interaction between the high elevation specialists of the genus Psudochelidura and the widespread euryoic species of the F. auricularia species group. Unfortunately, we do not have previous data on the presence of F. mediterranea (even under the name of F. auricularia ) at high elevations in Sierra Nevada.

Most of the area occupied by E. analis is currently under the protection of the Sierra Nevada National Park, so we do not expect immediate threats for the survival of the species other than the consequences of climate change, including a likely reduction of their presence area. It is imperative to acknowledge that the coexistence of species from the F. auricularia complex in the same areas as E. analis may constitute a potential threat to the latter species. This is attributed to the fact that species within the F. auricularia complex exhibit substantial competitive abilities, and the ongoing climatic changes are fostering their adaptation to higher altitudes ( Pavón-Gozalo et al. 2011). We believe it is important to determine if the populations of E. analis from Sierra de Filabres still exist or if they have already disappeared. In this respect, we like to call attention to the record of a specimen of Chelidura , reported in Fontana et al. (2021) from Pico de Veleta, treated as doubtful by Jurado-Angulo et al. (2021), but that requires further exploring.

Figures

Fig. 7. Bayesian phylogenetic tree based on cytb sequences of Eulithinus Hincks, 1935 and Pseudochelidura Verhoeff, 1902. Species and clade names correspond to the new classification adopted in this work. Posterior probabilities are indicated above branches. Background colours represent species and names below branches represent geographic areas.

Fig. 10. General view of the habitat and natural history notes of Eulithinus analis (Rambur, 1838) in Sierra Nevada (Spain). A. Typical landscape occupied by E. analis; in front Laguna de Río Seco, where numerous female specimens were observed taking care of their eggs under stones in August. B. Two females taking care of their eggs under the same stone at Laguna de Río Seco; note the remains of a dead male on the left, and the different development degree of the two egg masses; a few minutes later, females clustered the eggs into compact masses. C. Male with intermediate long sized cerci running in alert display at Pradollano. D. Last instar nymph from Laguna de Río Seco; note the general similarity with nymphs of Pseudochelidura cantabrica (Cuesta et al. 2023: fig. 5c). Photographs by MG-P.

Fig. 9. Habitus of live specimens of Eulithinus analis (Rambur, 1838) from Sierra Nevada (Spain). A. Male specimen with long cerci from Pradollano. B. Typical female with dark coloration and brown head from Pradollano. C. Male with intermediate sized cerci from Borreguiles del Río San Juan (MNCN_Ent433449). D. Light colored female with reddish head and pronotum from Pradollano. E. Male displaying short cerci from Laguna de Río Seco (MNCN_Ent344345). F. Male with each cercus of different size from Laguna de Río Seco. Photographs ex situ by MG-P.