The Coume Ouarnède System, a Hotspot of Subterranean Biodiversity in Pyrenees (France)
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diversity Article The Coume Ouarnède System, a Hotspot of Subterranean Biodiversity in Pyrenees (France) Arnaud Faille 1,* and Louis Deharveng 2 1 Department of Entomology, State Museum of Natural History, 70191 Stuttgart, Germany 2 Institut de Systématique, Évolution, Biodiversité (ISYEB), UMR7205, CNRS, Muséum National d’Histoire Naturelle, Sorbonne Université, EPHE, 75005 Paris, France; [email protected] * Correspondence: [email protected] Abstract: Located in Northern Pyrenees, in the Arbas massif, France, the system of the Coume Ouarnède, also known as Réseau Félix Trombe—Henne Morte, is the longest and the most complex cave system of France. The system, developed in massive Mesozoic limestone, has two distinct resur- gences. Despite relatively limited sampling, its subterranean fauna is rich, composed of a number of local endemics, terrestrial as well as aquatic, including two remarkable relictual species, Arbasus cae- cus (Simon, 1911) and Tritomurus falcifer Cassagnau, 1958. With 38 stygobiotic and troglobiotic species recorded so far, the Coume Ouarnède system is the second richest subterranean hotspot in France and the first one in Pyrenees. This species richness is, however, expected to increase because several taxonomic groups, like Ostracoda, as well as important subterranean habitats, like MSS (“Milieu Souterrain Superficiel”), have not been considered so far in inventories. Similar levels of subterranean biodiversity are expected to occur in less-sampled karsts of central and western Pyrenees. Keywords: troglobionts; stygobionts; cave fauna Citation: Faille, A.; Deharveng, L. The Coume Ouarnède System, a Hotspot of Subterranean Biodiversity in Pyrenees (France). Diversity 2021, 1. Introduction 13 , 419. https://doi.org/10.3390/ Stretching at the border between France and Spain, the Pyrenees are known as one d13090419 of the subterranean hotspots of the world [1]. This remarkable diversity is unevenly distributed along the Pyrenean range, reaching its highest value on the northern slope of Academic Editors: Michael Wink central and western Pyrenees. and Spyros Sfenthourakis The Arbas massif is located on the northern slope of central Pyrenees, about 70 km Received: 7 August 2021 south of Toulouse, at the limit of the departments of Haute-Garonne in the west and Ariège Accepted: 27 August 2021 in the east (Figure1). Extending the Lestelas massif to the west, it develops north of the Published: 31 August 2021 Bouigane valley, east of the Ger valley, and south of rolling hills of Comminges. It ranges from 500 m to 1608 m in altitude. Publisher’s Note: MDPI stays neutral The massif is formed by relatively complex series of Mesozoic limestones, generally with regard to jurisdictional claims in overlaid by massive Urgonian limestones [2]. Under high rainfall exceeding 2000 mm a published maps and institutional affil- year, the massif is mostly covered by beech forest, with small stands of fir locally. Water iations. transfers are very rapid due to a well-organized drainage and high surface karstification [2]. Not under threat and not under formal protection measures, the biological richness of the massif is nevertheless remarkable, and has been labeled as Zone Naturelle d’Intérêt Écologique, Faunistique et Floristique (ZNIEFF) Massifs d’Arbas, Paloumère et Cornudère Copyright: © 2021 by the authors. (national ID: 730011048). Licensee MDPI, Basel, Switzerland. The main cave system of the massif is the Réseau Félix Trombe—Henne Morte, from This article is an open access article the name of the French engineer and caver Félix Trombe, also known for his pioneer distributed under the terms and works on solar energy. This large system is commonly called Coume Ouarnède or Coumo conditions of the Creative Commons d’Hyouernedo by cavers. It was explored for years by the famous speleologist Norbert Attribution (CC BY) license (https:// Casteret who often referred to these explorations in his writings (see [3] for a list of creativecommons.org/licenses/by/ references) and remains a well-known cave system for speleologists worldwide. 4.0/). Diversity 2021, 13, 419. https://doi.org/10.3390/d13090419 https://www.mdpi.com/journal/diversity Diversity 2021, 13, x FOR PEER REVIEW 2 of 18 Diversity 2021, 13, 419 2 of 17 Casteret who often referred to these explorations in his writings (see [3] for a list of refer- ences) and remains a well-known cave system for speleologists worldwide. FigureFigure 1.1. Location of the the Arbas Arbas massif, massif, in in central central French French Pyrenees. Pyrenees. VariousVarious taxon-centeredtaxon-centered studies studies since since more more than than one one century century ago progressivelyago progressively brought tobrought light thatto light the that Coume the Coume Ouarn Ouarnèdeède system system hosted hosted a high a high diversity diversity of of cave cave animals.animals. In theIn the only only global global synthesis synthesis of of its its fauna, fauna, published in in 1982, 1982, 29 29 cave-restricted cave-restricted species species were were listedlisted fromfrom the the system, system, including including 18 18stygobionts stygobionts and and 11 troglobionts 11 troglobionts [4]. Today, [4]. Today, that is, that 40 is, 40years years later,later, there there are are38 cave-restricted 38 cave-restricted species species recorded, recorded, including including 21 stygobionts 21 stygobionts and 17 and 17troglobionts, troglobionts making, making of ofthe the Coume Coume Ouarnède Ouarnè dethe therichest richest cave cave fauna fauna of the of thePyrenees, Pyrenees, which is itself a major European hotspot. The richness of the Pyrenean range can be ex- which is itself a major European hotspot. The richness of the Pyrenean range can be plained by its biogeographical history [5]. The richness of the Coume Ouarnède can be explained by its biogeographical history [5]. The richness of the Coume Ouarnède can explained by the great extent of the cave system and the diversity of its subterranean hab- be explained by the great extent of the cave system and the diversity of its subterranean itats. It may also result from the relatively good knowledge we have of its fauna, as the habitats. It may also result from the relatively good knowledge we have of its fauna, as the system is close to the renowned Subterranean Laboratory of Moulis where a number of system is close to the renowned Subterranean Laboratory of Moulis where a number of biospeologists from all over the world have worked for decades. biospeologists from all over the world have worked for decades. In the framework of the special issue of the journal “Diversity” that deals with world hotspotsIn the of frameworksubterranean of biodiversity, the special issue the Coume of the journalOuarnède “Diversity” clearly deserves that deals some with atten- world hotspotstion. We ofshall subterranean provide inbiodiversity, this paper an the updated Coume and Ouarn comprehensiveède clearly deserves checklist some of its attention. sub- Weterranean shall provide fauna, put in this in its paper ecological an updated and biogeographical and comprehensive context. checklist of its subterranean fauna, put in its ecological and biogeographical context. 2. The Coume Ouarnède System 2. The Coume Ouarnède System The Coume Ouarnède system is the longest subterranean system of France, and one of theThe most Coume famous Ouarn sitesède regarding system isFrench the longest speleology. subterranean Today, it system has a development of France, and of one ofmore the mostthan 112 famous km for sites a depth regarding of 1020 French m, wi speleology.th 57 inter-connected Today, it has caves, a development while the massif of more thanof Arbas 112 kmhas forabout a depth 500 caves of 1020 in total m, with (Figur 57es inter-connected 2 and 3) ([6]; S. caves, Clément while pers. the comm. massif of Arbas05.2021). has The about network 500 caves offers in a totalgreat (Figures variety of2 and geomorphological3) ([ 6]; S. Clément features, pers. with comm. countless 05.2021). The network offers a great variety of geomorphological features, with countless fossil and active galleries and shafts, some of large dimensions (Pont de Gerbaut, Pène Blanque), and subterranean rivers [7]. Diversity 2021, 13, x FOR PEER REVIEW 3 of 18 Diversity 2021, 13, x FOR PEER REVIEW 3 of 18 fossil and active galleries and shafts, some of large dimensions (Pont de Gerbaut, Pène Blanque), and subterranean rivers [7]. Thefossil Coume and activeOuarnède galleries system and hasshafts, two some distinct of large resurgences: dimensions the (P ontGoueil de Gerbaut, di Her atPène Ar- Blanque), and subterranean rivers [7]. bas, and the Hount deras Hechos at Herran, 2.5 km to the west (“Hount-des-Heretchos” The Coume Ouarnède system has two distinct resurgences: the Goueil di Her at Ar- sensu [8]bas, and and [9], the that Hount is, «the deras source Hechos of atthe Herran, ash trees» 2.5 km after to the[10]). west The (“ Hount-des-Heretchos”Goueil di Her is the resurgencesensu of [8] the and main [9], thathydr is,ological «the source system, of the the ash Réseau trees» after Félix [10]). Trombe. The Goueil The Hountdi Her is deras the Hechos resurgenceis the resurgence of the main of hydrthe smallerological system,Henne theMorte Réseau system, Félix Trombe.regarded The as Hounta secondary deras derivationHechos of the is themain resurgence system [2,7]. of the The smaller two Hennesystems Morte are interconnected.system, regarded as a secondary Diversity 2021, 13, 419 derivation of the main system [2,7]. The two systems are interconnected. 3 of 17 Figure 2. Coume Ouarnède. Synthesis of the networks (modified from [7] and S. Clément pers. comm.). 1–9: Localities with threeFigure or 2. more Coume listed Ouarnède. species, Synthesis by decreasing of the netw speciesorks (modified richness. from 1: Goueil [7] and di S. Her; Clément 2: Grotte pers. decomm.). Pène Blanque;1–9: Localities 3: Poudac Gran;with 4: Hount three or deras more Hechos;listed species, 5: Henne by decreasing Morte; species 6: Puits richness.