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Comme on l'a déjà discuté dans des publications précédentes [1–3], les scorpions humicoles sont globalement rares. À Madagascar, les scorpions du sol les mieux étudiés sont représentés par les membres de la famille endémique des Microcharmidae [4–6]. Microcharmus Lourenço, 1995 a été le premier genre décrit pour cette famille [4], suivi de la description de deux autres genres : Neoprotobuthus Lourenço, 2000 [7] et Ankaranocharmus Lourenço, 2004 [2]. Pseudouroplectes Lourenço, 1995 [4], un genre de scorpion Buthidae du sol, a été décrit à partir de deux femelles collectées dans des formations de végétation arides du Sud-Ouest de Madagascar, à Andramanoetse Be, plateau Mahafaly, province de Toliara. Quelques années après, un autre spécimen de Pseudouroplectes, P. pidgeoni Lourenço et Goodman, 1999, a été collecté dans les forêts sèches du parc national d'Andohahela (parcelle 2), province de Toliara [8]. Le spécimen a été collecté dans un échantillon de sol d'une formation arbustive épineuse du parc, très voisine de la zone de transition entre les formations forestières sèche et humide. Jusqu'à la présente étude, à notre connaissance, aucun autre spécimen appartenant au genre Pseudouroplectes n'a été collecté. Entre temps, seule une étude ultra-structurale comparative avec le genre Microcharmus a été développée, confirmant ainsi la place du genre Pseudouroplectes au sein de la famille des Buthidae [2].
Le Dr. Brian Fisher et ses collègues de l'Académie des sciences de Californie ont mené, au cours des dernières années, des inventaires systématiques sur les invertébrés de diverses régions de Madagascar, y compris celles des formations végétales arides. Pour cela, ils ont employé des pièges, ainsi que diverses méthodes d'extraction du sol. De tels inventaires ont conduit à la collecte de plusieurs exemplaires de Pseudouroplectes, tous dans des zones à végétation sèche, confirmant ainsi un modèle de répartition limité à ce type de formation. De plus, plusieurs spécimens, collectés dans le Sud-Ouest de l'île, appartiennent à une nouvelle espèce décrite à présent.
Le modèle de distribution présenté par le genre Pseudouroplectes
La répartition du genre Pseudouroplectes, initialement fondée sur les deux premières espèces décrites, se limitait aux forêts sèches de l'Extrême-Sud de l'île. À présent, ce modèle de distribution est conforté par des nouvelles collectes de ces deux espèces. La description d'une nouvelle espèce de Pseudouroplectes élargit la répartition connue du genre vers le nord, dans les terres basses du Sud-Ouest de Madagascar. P. betschi et P. pidgeoni présentent, de toute évidence, une zone de parapatrie, voire même de sympatrie, dans le Sud de l'île. La distribution du genre Pseudouroplectes exclusivement dans des formations végétales sèches ou arides composées d'arbustes épineux pourrait être imputée à des échantillonnages insuffisants dans d'autres parties de l'île. Cette hypothèse semble pouvoir être écartée a priori car, si les Pseudouroplectes sont des scorpions rares, des échantillonnages systématiques avec utilisation de techniques similaires ont été employés dans différentes régions de l'île, avec des résultats positifs uniquement pour le Sud et le Sud-Ouest. La découverte des Pseudouroplectes dans le Sud et Sud-Ouest de Madagascar exclusivement semble, au contraire, plaider en faveur de facteurs biogéographiques historiques bien plus anciens, qui sont confortés par les affinités des Pseudouroplectes avec des éléments africains relictuels, mais aussi par la très grande ancienneté de cette lignée de scorpions.
1 Introduction
As already discussed in previous papers [1–3], soil scorpions are universally rare. In Madagascar, the best-studied soil scorpions are represented by members of the endemic family Microcharmidae [4–6]. Microcharmus Lourenço was the first genus to be described in this family [4], followed by the description of two other genera: Neoprotobuthus Lourenço [7] and Ankaranocharmus Lourenço [2]. Pseudouroplectes Lourenço [4], a buthid genus of soil scorpions, was described based on two females collected in dry southwestern vegetation formations at Andramanoetse Be, Plateau Mahafaly, Toliara Province. A few years later, another Pseudouroplectes specimen, P. pidgeoni, was collected in the extreme southeastern dry forests of the ‘Parc national d'Andohahela’ (parcel 2), Toliara Province [8]. This animal was collected in a soil litter sample in a spiny bush parcel of the reserve, within a few kilometres of the ecotone between dry and wet forest formations. Until the specimens reviewed in the current paper were collected, no additional material to our knowledge was obtained of the genus Pseudouroplectes. In the interim period, a comparative ultra-structural study was carried out with the genus Microcharmus and confirms the position of the genus Pseudouroplectes as an element of the family Buthidae [2].
Dr. Brian Fisher and colleagues at The California Academy of Sciences have been conducting systematic invertebrate inventories at various sites across Madagascar, including the dry vegetational formations, over the past few years and employ pit fall traps and different methods of soil litter extraction. These inventories lead to the collection of several specimens of Pseudouroplectes, all from dry vegetation sites, further supporting the pattern that this genus is restricted to that formation. Moreover, several specimens of Pseudouroplectes from these new collections obtained in the southwestern portion of the island belong to a new species, described here.
2 The pattern of distribution presented by the genus Pseudouroplectes
The distributional pattern of this genus, based on the two previously known species of Pseudouroplectes, is restricted to the extreme southern dry forest formations (Fig. 1). This geographic range is further supported by the more recent collections (see below). The description of a new species herein extends the known distribution of the genus slightly further to the north in the lowland regions of southwestern Madagascar. P. betschi and P. pidgeoni apparently present a parapatric or even a small sympatric zone of distribution in the extreme southern portion of the island. The distribution of the genus Pseudouroplectes exclusively in spiny bush and transitional spiny bush-dry deciduous vegetational formations could possibly be attributed to the lack of appropriate collecting methods in other parts of the island. This hypothesis can be eliminated a priori, since similar sampling methods have been used in all the different regions of the island. The exclusive presence of the genus Pseudouroplectes in the southern and southwestern portions of the island, in rather unique and highly endemic plant formations, can, however, be attributed to historical biogeographical factors. This idea is supported by the phylogenetic affinities of Pseudouroplectes with African relict elements [5] and particularly associated with the antiquity of this scorpion lineage.
Map of the southern portion of Madagascar showing the known distribution of Pseudouroplectes species overlaid on certain bioclimatic parameters.
Pseudouroplectes betschi: Andramanoetse Be, ‘Plateau Karimbola’ [= Plateau Mahafaly]; ‘Réserve spéciale de Cap-Sainte-Marie’ (25°35′40′′S–45°8′49′′E).
Pseudouroplectes pidgeoni: Parc national (formerly a ‘Réserve naturelle intégrale’) d'Andohahela (parcel 2), ‘Forêt de Manantalinjo’ (24°49′1′′S–46°36′36′′E); ‘Parc National de Tsimanampetsotsa’, ‘Forêt de Bemanateza’ (23°59′32′′S–43°52′50′′E); Mitoho Cave (24°2′50′′S–43°46′11′′E); 6.7 km 130° southeast of Efoetse (24°06′02′′S–43°45′36′′E); ‘Réserve spéciale de Cap-Sainte-Marie’ (25°35′40′′S–45°8′49′′E); Plateau Mahafaly, 6.2 km ENE of Itampolo (24°39′13′′S–43°59′48′′E).
Pseudouroplectes maculatus sp.n.: ‘Forêt de Beroboka’ (22°19′59′′S–43°21′59′′E), (22°13′59′′S–43° 21′59′′E); Ranobe (23°02′22′′S–43°36′37′′E – spiny forest-thicket); Ranobe (23°02.351′S–43°36.692′E – riparian forest); ‘Forêt de Tsinjoriaky’ (22°48′8′′S–43°25′14′′E).
The western portion of Madagascar receives less annual precipitation and has a more pronounced dry season than the eastern and central highland areas of the island. Along the west coast there is a pronounced north-south cline in decreasing annual rainfall from 1503 mm at Mahajanga, 780 mm at Morondava, 496 mm at Morombe, and 390 mm at Toliara [9]. Following this cline, the shift in rainfall gives rise to changes in vegetational types that range from deciduous forest in the northwest to a notably drier deciduous forest along the west-central lowland area, and then a sub-arid spiny bush towards the southwest. The transition zone between the dry deciduous forest and spiny bush transition falls between Belo-sur-Mer and Toliara, and more precisely in the region of the ‘Forêt des Mikea’, defined as the lowland area between the zone north of Toliara to Morombe, exactly the region where specimens of P. maculatus were collected. Other scorpion species known from the ‘Forêt des Mikea’ include Grosphus olgae and Neogrosphus griveaudi (Family Buthidae) [10]. As currently understood all records of P. maculatus sp.n. are north of the Onilahy River and those of P. betschi and P. pidgeoni south of the Onilahy River. The Forêt des Mikea is known to be a zone of considerable micro-endemism across a broad range of animal taxa [11–13].
3 Taxonomic treatment
Family Buthidae C.L. Koch, 1837
Genus Pseudouroplectes Lourenço, 1995
Pseudouroplectes maculatus sp.n. (Figs. 2–10)
Pseudouroplectes maculatus sp.n. 2–7. Male holotype. 2. Disposition of granulations on the dentate margins of the pedipalp chela movable finger. 3–4. Extremity of pedipalp chela movable finger, external and internal aspects. 5–7. Trichobothrial pattern. 5–6. Patella, dorsal and external aspects. 7. Femur, dorsal aspect. 8–9. Male paratype. 8. Ventral aspect, showing coxapophysis, sternum, genital operculum, pectines and sternite III. 9. Sternite V, showing oval-shape spiracles.
Pseudouroplectes maculatus sp.n. Female paratype (Forêt de Beroboka). Habitus.
CAS = California Academy of Sciences, San Francisco.
MGF = Madagascar Frontier Project
MNHN = ‘Muséum national d'histoire naturelle’, Paris.
Type material. Male holotype. Madagascar, Toliara Province, ‘Forêt de Beroboka’, 6.9 km 131° SE Ankidranoka (22°19′59′′S–43°21′′59′′E), 80 m alt., 12–16 March 2002 (Fisher and Griswold et al.), general collecting, tropical dry forest (CAS). Paratypes. Toliara Province, ‘Forêt de Beroboka’, 5.9 km 131° SE Ankidranoka (22°13′59′′S–43°21′59′′E), 80 m alt., 12–16 March 2002 (Fisher and Griswold et al.), pitfall trap, in tropical dry forest 1 male (CAS), 1 female (MNHN). Toliara Province, Ranobe (23°02′22′′S–43°36′37′′E), 30 m alt., spiny forest-thicket, EH11 sifted litter (leaf mold, rotten wood), 5–28 January 2003 (Frontier Project, MGF 054), 1 male (CAS). Ranobe (23°02 351′S–43°36 692′E), riparian Forest, 20 m alt., general collecting 22–29 April 2003 (Frontier Project, 2003-MGF 067), 1 male (MNHN). Forêt de Tsinjoriaky (22°48′8′′S–43°25′14′′E), 6.2 km 84°E Tsifota, 70 m alt., 6–10 March 2002 (Fisher and Griswold et al.), general collecting, spiny forest-thicket, 2 male juveniles (CAS–MNHN).
Etymology. The specific name makes reference to the dark pigmentation of the new species.
Diagnosis. Small scorpions, when compared with the average size of most species of micro-buthid genera, and measuring up to 15.87 mm in total length (see morphometric values). General coloration dark reddish-yellow with blackish spots over the body and appendages. Granulations strongly marked on body and appendages.
Relationships. The new species can be readily distinguished from all the other species of the genus Pseudouroplectes Lourenço, by (i) body, pedipalps and legs intensely marked with blackish spots, (ii) strongly marked carinae on tergites and metasomal segments, and (iii) presence of a conspicuous spinoid posterior granule on dorsal and subdorsal carinae of metasomal segments I–III.
Description based on male holotype.
Coloration. Basically dark reddish-yellow with blackish spots over the body and appendages. Carapace, pedipalps, and legs with variegated blackish spots; tergites with four longitudinal blackish stripes; dorsal and subdorsal carinae of metasomal segments I–III densely spotted. Venter and chelicera yellowish without spots.
Morphology. Carapace with a strongly marked granulation; anterior margin almost straight. Carinae weak; furrows inconspicuous. Median ocular tubercle distinctly on the anterior third of the carapace; median eyes separated by a little more than one ocular diameter. Three pairs of lateral eyes. Sternum subpentagonal. Mesosoma: tergites strongly granular. Median carina moderate in all tergites. Tergite VII pentacarinate. Venter: genital operculum divided longitudinally, each plate having a more or less subtriangular shape. Pectines large: pectinal tooth count 16–16 (male paratypes with 15–16 and 16–16); basal middle lamellae of the pectines not dilated; fulcra absent. Sternites smooth with short semi-slit-like spiracles; VII with a few granulations and vestigial carinae. Metasoma: segments I to IV with 10 carinae, crenulate; ventral carinae vestigial on segments III–IV; intercarinal spaces weakly granular. Segment V rounded with five carinae. Telson with a very elongated ‘pear-like’ shape, smooth with strong setation; aculeus short, weakly curved; subaculear tooth absent. Cheliceral dentition characteristic of the family Buthidae [14]; fixed finger with two moderate basal teeth; movable finger with two very weak and fused basal teeth; ventral aspect of both finger and manus with dense, long setae. Pedipalps: femur pentacarinate; patella with seven carinae; internal face of patella with 4–5 spinoid granules; chela with vestigial carinae; all faces moderately granular. Fixed and movable fingers with 6–7 almost linear rows of granules; two accessory granules present at the base of each row; extremity of fixed and movable fingers with one long and sharp denticle. Trichobothriotaxy; orthobothriotaxy A-α [15,16]. Legs: tarsus with very numerous fine median setae ventrally. Pedal spurs reduced; tibial spurs absent.
Morphometric values (in mm) of the holotype. Total length, 15.87. Carapace: length, 2.18; anterior width, 1.36; posterior width, 2.21. Metasomal segment I: length, 1.18; width, 1.22. Metasomal segment V: length, 2.72; width, 0.93; depth, 0.92. Vesicle: width, 0.77; depth, 0.78. Pedipalp: femur length, 1.63; width, 0.46; patella length, 1.99; width, 0.82; chela length, 2.85; width, 0.61; depth, 0.59; movable finger length, 1.97.
Key to the known species of Pseudouroplectes is given in Table 1.
Key to the known species of Pseudouroplectes
| 1. Pale scorpions, yellowish to reddish-yellow, with or without spots | 2 |
| (1) Dark scorpions with several blackish scorpions over the body and appendages | P. maculatus sp.n. |
| 2. Coloration yellowish without any spots; female pectinal tooth count 18/19 | P. betschi |
| (2) Coloration yellowish with four longitudinal reddish-brown strips over the tergites; female pectinal tooth count 14/15 | P. pidgeoni |
Acknowledgements
We are very grateful to Mr. Bernard Duhem, Muséum, Paris for preparing the drawings and to Lucienne Wilmé, for the preparation of the map. Specimens were made available by Frontier-Madagascar (Society for Environmental Exploration) through Hannah Thomas and Annette Olsson. Field collections were funded in part by National Science Foundation (USA) awards to Brian L. Fisher and Charles E. Griswold (DEB-0072713) and to Brian L. Fisher and Phil S. Ward (DEB-0344731).