Bernard Duhem

Wilson R. Lourenço

CR Biologies

C. R. Biologies 332 (2009) 1085–1091Ecology / ÉcologieThe genus Vachoniochactas González-Sponga (Scorpiones,Chactidae), a model of relictual distribution in past refugiaof the Guayana region of South AmericaWilson R. Lourenço a,∗, Bernard Duhem ba Muséum national d’histoire naturelle, département de systématique et évolution, section arthropodes (arachnologie), CP 053,57, rue Cuvier, 75005 Paris, Franceb Muséum national d’histoire naturelle, département de systématique et évolution, CP 039, 12, rue Buffon, 75005 Paris, FranceReceived 30 July 2009; accepted after revision 4 September 2009Available online 27 October 2009Presented by Paul OzendaAbstractA new species, Vachoniochactas roraima sp. n. (Chactidae) is described from Mount Roraima, a site located on the bordersof Brazil, Guyana and Venezuela. The description of the new species brings further evidence to the biogeographic pattern ofdistribution presented by the genus Vachoniochactas, as an endemic element to the Tepuys formations of South America. To citethis article: W.R. Lourenço, B. Duhem, C. R. Biologies 332 (2009).© 2009 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.RésuméLe genre Vachoniochactas González-Sponga (Scorpiones, Chactidae), un modèle de distribution relictuelle dans des re-fuges passés de la région Guayana d’Amérique du Sud. Une nouvelle espèce, Vachoniochactas roraima sp. n. (Chactidae) estdécrite du Mont Roraima, situé dans la zone frontalière entre le Brésil, la Guyana et le Venezuela. La description de cette nouvelleespèce apporte un nouvel appui au modèle de distribution géographique présenté par le genre Vachoniochactas, en tant qu’un élé-ment endémique de la région des Tepuys en Amérique du Sud. Pour citer cet article : W.R. Lourenço, B. Duhem, C. R. Biologies332 (2009).© 2009 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.Keywords: Scorpiones; Vachoniochactas; New species; Guayana; Tepuys; EndemismMots-clés : Scorpiones ; Vachoniochactas ; Nouvelle espèce ; Guayana ; Tepuys ; Endémisme* Corresponding author.E-mail address: arachne@mnhn.fr (W.R. Lourenço).1631-0691/$ – see front matter © 2009 Académie des sciences. Published bdoi:10.1016/j.crvi.2009.09.0061. IntroductionThe genus Vachoniochactas was described by Gon-zález-Sponga [1] to accommodate a new species, V. la-sallei González-Sponga, 1978, collected in the ‘CerroVenamo’ state of Bolívar in Venezuela. The genusy Elsevier Masson SAS. All rights reserved.1086 W.R. Lourenço, B. Duhem / C. R. Biologies 332 (2009) 1085–1091remained monotypic until the discovery and descrip-tion of a second species, Vachoniochactas amazonicusGonzález-Sponga, 1991 [2] from the Venezuelan slopesof ‘Cerro de la Neblina’. Subsequently, Lourenço [3]described a third species belonging to this genus, Va-choniochactas ashleeae, this time from the Brazilianslopes of the ‘Pico da Neblina’ (= ‘Cerro de la Nebli-na’). Very recently, Flórez et al. [4] described one morenew species, V. humboldti from the Vichada departmentof Colombia, region located in the extreme East of thecountry, in the border with Venezuela.All the species of Vachoniochactas, so far described,have been collected in the ‘mountain’ formations de-fined as the Tepuys distributed mainly in Venezuela,Brazil, Guyana and Colombia. The Tepuys region cor-responds largely to the Guayana, a floristic lowlandprovince that has been delineated botanically [5].In the present Note, another new species of Vacho-niochactas is described from another Tepuys forma-tion, ‘Mount Roraima’, located on the borders of Brazil,Guyana and Venezuela. The description of this newspecies brings further evidence of the biogeographicpattern of distribution of the genus Vachoniochactaswhich is confirmed as an endemic element present onlyin the Tepuys formations of South America.2. The Tepuys formations and Mount RoraimaThe Tepuys (or Tepuis) are table-top mountains(mesas) found only in the Guayana highlands of SouthAmerica. They consist of rather isolated entities, andpresent few connected ranges. This geographical partic-ularity makes the Tepuys outstanding endemic centresfor both plants and animals. From a geological point ofview the Tepuys are composed of sheer blocks of Pre-cambrian sandstone and quartzite rocks. These ‘mesas’are the remains of a large sandstone plateau that oncecovered the granite basement complex between what istoday the northern border of the Amazon Basin and theOrinoco, between the Atlantic coast and the Rio Negro.Throughout the course of the Earth’s geological historythe plateau has been eroded and the Tepuys formed fromthe remaining inselbergs (monadnocks). The plateauxof these ‘mesas’ are completely isolated from the low-lying forest, making them ‘ecological islands’. How-ever, the altitude engenders a different climate fromthat of lowland forest. The tops enjoy cool temperatureswith frequent rainfall, while the bases of the mountainshave a warm and humid tropical climate. The 2734-meter high Mount Roraima represents the triple borderlandmark of Brazil, Venezuela and Guyana. Its verticalscarps can exceed 500 meters in height and are formedof nearly 2 billion year old sandstones. Geologically,it represents a stratigraphic landmark of the RoraimaSupergroup, a Paleoproterozoic age sedimentary basinof the Guyana Shield, north of the Amazonian Craton[6–8].3. Biogeography of Tepuys; palaeoclimates refugia(endemic centres)As explained in a recent publication [9], the uniquefloral biota of the Guayana Highlands was formerlyconsidered to be the result either of vicariance afterlong evolution in isolation, or of dispersal by successiveconnection and disconnection of summit floras due toPleistocene climatic changes. Accordingly, ‘dispersal-ists’ adopted the refuge hypothesis [10–12] as a mecha-nism for genetic differentiation. This hypothesis invokesthe alternation of dry and wet climates due to the re-currence of glacial and interglacial phases, respectively.Glacial aridity would have determined the fragmenta-tion of forests into refugia with wet, stable climatessurrounded by dry forest or savannah formations. Inter-glacials on the other hand, would have been character-ized by forest expansion and coalescence throughout theentire Neotropical lowlands. The associated diversifica-tion model suggests allopatric speciation within forestrefugia which are still recognizable by their high biodi-versity and endemism.Rull [9] rejects, in part, the model of classical refu-gia and proposes instead one of diversification. This isbased on the following observations from recent palyno-logical data: (i) Vertical shifts and biotic interconnectionamong Tepuys summits triggered by glacial/interglacialalternation have indeed occurred. (ii) About half of thesummits would have remained isolated, so both vicari-ance and dispersal are needed to account for the long-term origin and evolution of the Pantepuy biota. (iii) TheGuayana highlands were not, however, a biotic refugeduring the Pleistocene glaciations [13–15]. Neverless,Rull assumes that these ‘keystone’ hypotheses shouldbe tested by further studies yet to be carried out.The patterns of distribution and differentiation ofscorpions have been used to define refugia, or at leastendemic centres in the neotropics [16,17]. The refu-gia of scorpions correspond closely with those pro-posed for other groups of plants and animals in partic-ular with those outlined by Prance [11,12] for woodyplants. The species of Vachoniochactas show a patternof biogeographical distribution over several Tepuys ofthe Guayana Highlands. V. amazonicus, V. ashleeae andV. humboldti are found on the ‘Imeri’ endemic cen-tre, which ranges from Brazil through Venezuela intoW.R. Lourenço, B. Duhem / C. R. Biologies 332 (2009) 1085–1091 1087Colombia. The first two species are distributed preciselyon the ‘Neblina-São Gabriel’ subcentre of ‘Imeri’. V.lasallei and V. roraima sp. n., are distributed more tothe East, on the ‘Imataca’ endemic centre. This includesboth ‘Venamo’ and ‘Roraima’ Tepuys.In the Guayana floristic province [5], major endemicareas defined as having the highest priority for conser-vation based on scorpion biodiversity, include ‘Imataca’and ‘West Guiana’ [17]. The inventory for scorpions inthe Guayana Highlands is far from complete. This canbe attested by the fact that, during the period of classicalstudies on scorpions, only two species of Broteochac-tas Pocock have been described from Mt. Roraima [18].Consequently, one can expect new species of Vacho-niochactas and other genera as well, to be found indifferent Tepuys.4. MethodsMeasurements and illustrations were made using aWild M5 stereo-microscope with a drawing tube (cam-era lucida) and an ocular micrometer. Measurementsfollow those of Stahnke [19] and are given in mm. Tri-chobothrial notations are those developed by Vachon[20] and the morphological terminology mostly followsthat of Hjelle [21].Taxonomic treatmentFamily Chactidae Pocock, 1893Genus Vachoniochactas González-Sponga, 1978In a reanalysis of several genera of chactids, thegenus Vachoniochactas was redefined, by Lourenço[16], as a group of species within the genus Broteochac-tas Pocock. Subsequently, it was reestablished as a validgenus by Sissom [22], a decision acknowledged byLourenço [3]. Flórez et al. [4] proposed a more com-plete diagnosis for Vachoniochactas. This diagnosis isadopted in the present study. For further details refer tothese authors.Vachoniochactas roraima sp. n. (Figs. 1, 2)Material. Frontier between Brazil, Guyana and Ve-nezuela, Mt. Roraima (1380 m), 15/V/1977, collectedby local Indians (Summer Institute leg.). Male holotype,male and female paratypes. Type material deposited inthe Muséum national d’Histoire naturelle, Paris.Etymology. The specific name is placed in apposi-tion to the generic name and refers to Mt. Roraima, thelocation in which the new species was collected.Diagnose. Small scorpions, 18 mm in total length,including telson (the species is the smallest ever de-scribed). Coloration reddish-yellow to reddish-brown,with pedipalps, legs and ventral aspect of female denselyspotted. Body and appendages weakly granulated orsmooth; carapace and tergites with minute punctationson male, smooth on female; metasomal segments andtelson weakly granulated on male, strongly granulatedon female; ventral aspect of metasomal segments IV–Vgranulated on both sexes. Pectines with 9 teeth on malesand 7 on females. Telson with 2–3 small granules underthe aculeus. Dentate margins on fixed and movable fin-gers of pedipalps with 6 almost linear rows of granules;Trichobothrial pattern type C, ‘majored’ neobothrio-taxy. Tarsi of legs with long thin setae.Vachoniochactas roraima sp. n. can be distinguishedfrom the other species in the genus Vachoniochactas,and in particular from Vachoniochactas lasallei whichoccurs in the nearby region of the ‘Cerro Venamo’ inVenezuela, by the following features: (i) smaller dimen-sions, with male and female identical in size, (ii) ab-sence of tubercles under the aculeus; only 2–3 granulescan be observed, (iii) ventral aspect of metasomal seg-ments III to V with granulations.Description (based on male holotype and male andfemale paratypes). Measurements follow the descrip-tion.Coloration. Basically reddish-yellow to reddish-brown, female densely spotted on pedipalps, legs andventral aspect. Prosoma: Carapace reddish-brown, dark-er in male. Tergites reddish-brown, as for the carapace,with two longitudinal yellowish strips. Metasomal seg-ments reddish-brown in male, reddish-yellow in female,with darker zones over carinae; vesicle reddish-yellowto reddish-brown. Chelicerae yellowish with diffusevariegated blackish spots only at the base of fingers;fingers yellowish with reddish teeth. Pedipalps reddish-yellow with dark spots over carinae. Legs yellowishwith transverse dark spots. Venter and sternites reddish-yellow, paler on female; variegated dark spots overcoxapophysis, sternum, genital operculum and sternites;pectines pale yellow.Morphology. Carapace punctuated in male, lustrousin female; carinae vestigial with some sparse granu-lations; furrows shallow; median eyes anterior to thecentre of the carapace; two pairs of lateral eyes. Ster-num pentagonal, wider than long. Tergites acarinate,with only minute punctuations in male, smooth andshiny with some granulations in female. Pectinal toothcount 9–9 in males (7–7 in female), fulcra absent. Stern-ites smooth and shiny; spiracles small, almost rounded.Metasomal segments I to IV wider than long; metaso-mal tegument punctuated and with some granulations inmale; strongly granulated in female. Vesicle punctuatedin male, granulated in female. Ventral carinae absent1088 W.R. Lourenço, B. Duhem / C. R. Biologies 332 (2009) 1085–1091Fig. 1. Vachoniochactas roraima sp. n. 1. Carapace. 2. Chelicerae. 3. Metasomal segment V and telson, lateral aspect (male holotype). 4–5. Sternum,genital operculum and pectines (male holotype and female paratype). 6–7. Leg IV (male holotype and female paratype).from segments I to V in male, weakly marked on seg-ments IV–V in female; dorsal carinae on segments I–IVwith one stronger spinoid granule. Pedipalps: Femurwith dorsal internal, dorsal external and ventral inter-nal carinae moderately marked; ventral external carinavestigial; dorsal and ventral faces with minute granu-lations; internal face weakly granular. Patella smoothand lustrous; dorsal internal, ventral internal, ventral ex-ternal and external carinae moderately marked; othercarinae vestigial. Chela smooth and lustrous; carinaeweakly marked to vestigial. Dentate margins on mov-able and fixed fingers composed of 6 almost linear rowsof granules. Chelicerae with the dentition typical of thefamily Chactidae [23], and with intense setation ven-W.R. Lourenço, B. Duhem / C. R. Biologies 332 (2009) 1085–1091 1089Fig. 2. Vachoniochactas roraima sp. n., male holotype. 8. Pedipalp, dorsal aspect, showing pigmentation pattern. 9. Idem, showing trichobothria.10–14. Trichobothrial pattern. 10–12. Chela, dorso-external, ventral and internal aspects. 13–14. Patella, ventral and external aspects.trally and internally. Trichobothriotaxy type C; ‘ma-jored’ neobothriotaxy [20]. Legs, tarsi with long andthin setae.Morphometric values (in mm) of the male holo-type and female paratype. Total length, 18.5/18.4 (in-cluding telson). Carapace: length, 2.6/2.9; anteriorwidth, 1.7/1.9; posterior width, 2.7/3.1. Mesosomalength, 4.8/5.2. Metasomal segments. I: length, 1.0/0.8;width, 1.7/2.0; II: length, 1.1/1.0; width, 1.7/1.9; III:length, 1.2/1.3; width, 1.6/1.8; IV: length, 1.8/1.7;width, 1.6/1.8; V: length, 2.8/2.6; width, 1.6/1.7; depth,1.3/1.5. Vesicle: length, 3.2/2.9; width, 1.4/1.4; depth,1.0/1.0. Pedipalp: femur length, 2.1/2.1, width, 0.8/0.9;patella length, 2.4/2.4, width, 0.9/1.0; chela length,3.5/4.1, width, 0.9/1.1, depth, 0.7/1.0; movable fingerlength, 2.1/2.3.1090 W.R. Lourenço, B. Duhem / C. R. Biologies 332 (2009) 1085–1091Fig. 3. Map of Northern South America showing the distribution of Vachoniochactas species in the Guayana Highlands. V. lasallei (black square),V. amazonicus (black star), V. ashleeae (black triangle), V. humboldti (black circle) and V. roraima sp. n. (black asterisk).AcknowledgementsWe are most grateful to Prof. John L. Cloudsley-Thompson, London, for useful comments to the manu-script, and to Elise-Anne Leguin, Museum, Paris, for thehelp with the preparation of the plates.References[1] M.A. Gonzáles-Sponga, Escorpiofauna de la region orientaldel Estado Bolivar, en Venezuela, Ed. Roto-Impresos, Caracas,1978.[2] M.A. González-Sponga, Arácnidos de Venezuela. Escorpionesdel tepui ‘La Neblina’, Territorio Federal Amazonas, Venezuela(Scorpionida: Chactidae: Buthidae), Bol. Acad. Cienc. Fis. Mat.Nat. 51 (1991) 95–136.[3] W.R. Lourenço, Scorpion biogeographic patterns as evidence fora Neblina-São Gabriel endemic center in Brazilian Amazonia,Rev. Acad. Col. Cienc. Exa. Fis. Nat. 19 (1994) 181–185.[4] E.D. Flórez, R. Botero-Trujillo, L.E. Acosta, Description ofVachoniochactas humboldti sp. nov. from Colombia, withcomplementary notes on the genus (Scorpiones, Chactidae),Zootaxa 1853 (2008) 31–44.[5] S.A. Mori, The Guayana lowland floristic province, C. R. Soc.Biog. 67 (1991) 67–75.[6] A. Gansser, Observations of the Guiana Shield (South America),Ecl. Geol. Helv. 47 (1954) 77–112.[7] S.K. Ghosh, Geology of the Roraima group and its implications,Simp. Amaz., 1, Puerto Ayacucho, Venezuela, Mem., 1981,pp. 22–30.[8] J.O.S. Santos, P.E. Potter, N.J. Reis, L.A. Hartmann, I.R.Fletcher, N.J. McNaughton, Age, source and regional stratigra-phy of the Roraima supergroup and Roraima-like sequences inNorthern South America, based on U–Pb geochronology, Geol.Soc. Am. Bull. 115 (2003) 331–348.[9] V. Rull, Biotic diversification in the Guayana Highlands: A pro-posal, J. Biog. 32 (2005) 921–927.[10] J. Haffer, Speciation in Amazonian forest birds, Science 165(1969) 131–137.[11] G.T. Prance, Phytogeographic support for the theory of Pleis-tocene forest refuges in the Amazon Basin, based on evidencefrom distribution patterns in Caryocaraceae, Chrysobalanaceae,Dichapetalaceae and Lecythidaceae, Acta Amaz. 3 (1973) 5–28.[12] G.T. Prance, Forest refuges: Evidence from woody angiosperms,in: G.T. Prance (Ed.), Biological Diversification in the Tropics,Columbia Univ. Press, New York, 1982, pp. 137–158.[13] V. Rull, Is the ‘Lost World’ really lost? Palaeoecological insightsinto the origin of the peculiar flora of the Guayana Highlands,Naturwissenschaften 91 (2004) 139–142.[14] V. Rull, An evaluation of the Lost World and Vertical Displace-ment hypotheses in the ‘Chimanta’ massif, Venezuelan Guayana,Gl. Ecol. Biog. 13 (2004) 141–148.W.R. Lourenço, B. Duhem / C. R. Biologies 332 (2009) 1085–1091 1091[15] V. Rull, Biogeography of the ‘Lost World’, a palaeoecologicalperspective, Earth-Sci. Rev. 67 (2004) 125–137.[16] W.R. Lourenço, Diversité de la faune scorpionique de la régionamazonienne ; centres d’endémisme ; nouvel appui à la théoriedes refuges forestiers du Pléistocene, Amazoniana 9 (1986) 559–580.[17] W.R. Lourenço, Scorpion diversity in Tropical South Amer-ica: Implications for conservation programs, in: Ph. Brownell,G.A. Polis (Eds.), Scorpion Biology and Research, Oxford Univ.Press, 2001, pp. 406–416.[18] R.I. Pocock, Myriopoda and Arachnida, in: Report on a collec-tion made by Messrs F.V. McConnell and J.J. Quelch at MountRoraima in British Guiana, in: Trans. Linn. Soc. London, Zool-ogy, ser. 2, 1900, pp. 64–71.[19] H.L. Stahnke, Scorpion nomenclature and mensuration, Entom.News 81 (1970) 297–316.[20] M. Vachon, Etude des caractères utilisés pour classer les familleset les genres de Scorpions (Arachnides). 1. La trichobothriotaxieen arachnologie. Sigles trichobothriaux et types de trichobothri-otaxie chez les Scorpions, Bull. Mus. Natl. Hist. Nat. 140 (1974)857–958.[21] J.T. Hjelle, Anatomy and morphology, in: G.A. Polis (Ed.), TheBiology of Scorpions, Stanford Univ. Press, 1990, pp. 9–63.[22] W.D. Sissom, Systematics, biogeography, and paleontology, in:G.A. Polis (Ed.), The Biology of Scorpions, Stanford Univ.Press, 1990, pp. 64–160.[23] M. Vachon, De l’utilité, en systématique, d’une nomenclaturedes dents des chélicères chez les Scorpions, Bull. Mus. Natl.Hist. Nat. 35 (1963) 161–166.

The genus <i>Vachoniochactas</i> González-Sponga (Scorpiones, Chactidae), a model of relictual distribution in past refugia of the Guayana region of South America

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The genus <i>Vachoniochactas</i> González-Sponga (Scorpiones, Chactidae), a model of relictual distribution in past refugia of the Guayana region of South America

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