The remarkable scorpion diversity in the Ecuadorian Andes and description of a new species of Tityus C. L. Koch, 1836 (Scorpiones, Buthidae)

Abstract A new species of Tityus, subgenus Atreus (Scorpiones: Buthidae) is described from the Province of Pichincha in the Ecuadorian Andes. Ecuadorian scorpion fauna remains one of the less well studied among those of South America. Nevertheless, some comments are addressed about its remarkable diversity and high level of endemic elements.

Although studies by Lourenço (1988Lourenço ( , 1995 represented the first attempt to produce a synthesis of the Ecuadorian scorpion fauna, these contributions probably only represented a small part of the fauna actually present in Ecuador. This conjecture is supported by the descriptions of new species from different regions of the country (e. g. Lourenço 2005Lourenço , 2007. In the winter (southern hemisphere) of 2012, scorpions were collected from mountains within the Ecuadorian Andes. Two specimens (1 male, 1 female) were discovered to be a new species belonging to the genus Tityus. Herein, we describe this new species and comment on the scorpion fauna found within the Ecuadorian region, and suggest several hypotheses regarding mechanisms that generated this remarkable diversity.

Methods
Illustrations and measurements were made with the aid of a Wild M5 stereo-microscope with a drawing tube (camera lucida) and an ocular micrometer. Measurements follow Stahnke (1970) and are given in mm. Trichobothrial notations follow Vachon (1974) while morphological terminology mostly follows Hjelle (1990). Etymology. Specific name refers to the strongly enlarged posterior metasomal segments.

Family
Diagnosis. Scorpions of medium size in relation to other species within the genus. Total length in male and female, 51.9 and 50.5 mm, respectively. General coloration reddish-brown with darker blackish zones; carapace and tergites with three longitudi-nal brownish stripes, separated by yellow zones. Metasomal segments flattened, comparatively to other species of the group; segments IV and V very strongly enlarged, especially in the male holotype. Dorsal carinae of metasomal II to IV terminating distally with two very strong spinoid granules, more distinct on the female paratype. Pectines small with 15-15 teeth on male and 15-14 on female; basal piece of the middle lamella strongly dilated on female, and oval in shape. Cutting edges of fixed and movable fingers of pedipalp chela with 12-13 and 12-14 rows of granules on the male and female, respectively.
Relationships. The new species is clearly allied to Tityus forcipula (Gervais, 1843) and other associated species such as Tityus spinatus Pocock, 1898 and Tityus cuellari Lourenço, 1994, species also known from the Colombian and Ecuadorian Andes and, previously defined as part of the Tityus forcipula complex (see Lourenço, 1984 for details). It can, however, be distinguished from all these species and in particular from T. forcipula by a number of features: (i) a distinct pattern of coloration and pigmentation, with brownish longitudinal stripes on the carapace and tergites, which are absent from the other species, (ii) sternites III to VII with a very strongly marked granulation but a moderately marked setation; granulations are less marked on the other species,  (iii) metasomal segments strongly flattened and very strongly enlarged, especially in the male holotype; less enlarged in the other species, (iv) tergites with only moderately marked granulation, (v) pedipalp segments and chela are smooth to lustrous; somewhat granular in the other species. Description based on male holotype and female paratype (measurements in Table 1). Coloration. Reddish-brown with darker, blackish areas. Prosoma: carapace reddish-brown, with yellowish zones between posterior median carinae. Mesosoma: reddish-brown with three brown to blackish longitudinal stripes extending from the posterior zone of the carapace and over tergites I to VII. Metasomal segments I to III reddish-brown, with dark to blackish carinae; IV and V reddish-brown dorsally, blackish laterally and ventrally. Vesicle: brownish-black; aculeus yellowish. Venter is reddish-brown, with some yellowish zones. Chelicerae yellowish-brown, with a very dark thread of variegated spots; fingers dark; teeth reddish. Pedipalps: reddish; fingers blackish, with extremities yellowish. Legs reddish-yellow to reddish-brown, with some diffuse and discrete fuscous spots; tarsi yellowish.
Morphology. Carapace moderately to strongly granular; anterior margin with a moderately marked concavity. Anterior median superciliary and posterior median carinae moderate to strong. Furrows moderately to strongly deep. Median ocular tubercle distinctly anterior to the centre of carapace. Eyes separated by a little more than one ocular diameter. Three pairs of lateral eyes. Sternum triangular. Mesosomal  Dorsal surface smooth; ventral surface weakly granular; subaculear tooth strong and spino-rhomboidal in shape. Cheliceral dentition characteristic of the family Buthidae (Vachon, 1963); movable finger with two basal teeth well distinct; ventral aspect of

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17 both fingers and manus with long, dense setae. Pedipalps: femur pentacarinate; patella with seven carinae; chela with nine carinae, more distinct on female paratype; all faces with only a few granules; smooth. Fixed and movable fingers of chela with respectively 12 and13 oblique rows of granules on the male holotype and 12-14 on the female paratype. Trichobothriotaxy; orthobothriotaxy A-α (alpha) (Vachon, 1974(Vachon, , 1975. Legs: tarsus with two series of 6-7 setae on ventral surface. Habitat. The new species inhabits the tropical forests of the Ecuadorian Andean Mountains, in the Pichincha Province. The specimens were collected at an altitude of 2200 m, inside of rotten Lauraceae logs.

The remarkable diversity of the Ecuadorian scorpion fauna
As already outlined by Lourenço (1994b), many if not most authors working on the floras and faunas of the Neotropical region seem to agree that the possible 'epicentre' of global diversity occurs in the tropical and subtropical Andean region (the upper Amazon, North of Peru, and most of Ecuador and Southern Colombia). This hypothesis is supported by studies conducted on various taxa (plants, vertebrates and butterflies (Gentry 1988(Gentry , 1992). In the same line of thinking, Lourenço (1994b) suggested that one of the areas exhibiting the highest alpha-diversity for scorpions in the world ranged from Southern Colombia, Ecuador, the Northeast region of Peru, and the Upper Amazon region of Brazil. This region has been already the subject of other previous research programs, namely the 'Transecto Ecuadorial Pacifico Amazonico', as defined by Van Velzen (1992). Despite studies such as these, there still remain important gaps in the knowledge of scorpion communities within the Andean region. By expanding the area studied eastward, it would allow for a more accurate survey of Colombia, Peru and Brazil.
The number of endemic taxa in this region is very high -more than 80% -and is comparable to the number of endemic taxa found in other previously studied regions such as Baja California (about 75%) (Williams 1980;Lourenço 1994b). However, desert areas such as Baja California are much better studied than tropical areas. Consequently, a substantial increase in the total number of species in North American deserts is unlikely. The use of ultra-violet light in the detection of scorpions in open areas such as deserts has been intense for many decades. On the other hand, inventory work in tropical forests is still fairly new and UV light is not as efficient in this type of habitat, mainly because of the landscape vegetation. Moreover, for several sections of the tropical forests such as the canopy, knowledge of the scorpion fauna is virtually non-existent (Lourenço and Pézier 2002). Consequently, the effective number of species in rainforests may be much greater than what is presently estimated; see Lourenço (1994b) for comparative numbers.
The scorpion fauna of the Ecuadorian Andes is characterized by an outstanding concentration of species belonging to genera such as Tityus and Teuthraustes Simon, 1878 (Chactidae). Within each genus, the species show to be closely related. The speciation pattern of the scorpions corresponds to the explosive model proposed by Gentry (1992) for plants of the genus Gasteranthus which have a similar range of distribution in this same area. The proposed mechanism operating process is associated with some type of genetic transilience associated with genetic drift in small founder populations, a process also postulated for Hawaiian Drosophila (Gentry 1992).