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Diversity
A large number of undescribed species is predicted because vaejovids are substratum specialists and occupy restricted distributional ranges. This combination of factors implies that α and β diversity of vaejovids should be greatest in regions of geological complexity (e.g. mountain ranges) and substratum heterogeneity (e.g. deserts), many of which remain poorly surveyed for scorpions. At least 60 new species have already been identified in museum collections but many parts of North America, particularly mainland Mexico, are poorly sampled, if at all (Lourenço & Sissom 2000; Sissom & Hendrixson, 2005). For example, recent fieldwork by W.D. Sissom confirms that inselbergs in Arizona and New Mexico alone harbor approximately 15 new species in the Vaejovis vorhiesi complex. Extrapolating from sampled areas with high known diversity to poorly sampled areas, more species in the vorhiesi complex should be found in the Sierra Madre Occidental and nearby isolated desert mountain ranges in western Mexico, where the group is presently unknown but where there is abundant suitable habitat. Numerous undescribed species are also expected in Pseudouroctonus, Serradigitus, Uroctonites, and the mexicanus and nitidulus groups of Vaejovis. In fact, with the exception of the Baja peninsula, Mexico remains very poorly sampled (Lourenço & Sissom 2000). Current knowledge of scorpion diversity and distribution on the Mexican mainland is based largely on sporadic ‘rock-rolling’ by general collectors, a technique that is inefficient and delivers a sample strongly biased toward rupicolous species. Many fossorial species, especially those occurring in sandy habitats, cannot be collected at all using this method. In contrast, nocturnal collecting with ultraviolet (UV) light detection (exploiting the fluorescence property of scorpion epicuticle) greatly increases yields and led to discovery of numerous undescribed species, even in areas previously thought to have been well-collected (Honetschlager 1965; Williams 1968, 1980; Stahnke 1972; Lamoral 1979 ; Sissom et al. 1990). For example, UV detection on expeditions to the Baja peninsula by S.C. Williams in the 1960s resulted in the description of 35 new species (58.3% of the current fauna), more than doubling the number known at the time. In addition, the number of species recorded from the peninsula was tripled because many described species were reported for the first time. The understanding of distributions for all species on the peninsula was also vastly improved. Even with all of this intensive collecting, undescribed species remain in Baja California: a new species of Paruroctonus and at least two new species of Vaejovis were collected during the first collecting trip for the REVSYS project (link to field trips and scorpions). Vaejovids constitute 83% of the Baja scorpion fauna (the figure for all of Mexico is about 70%). There is no doubt that intensive collecting efforts, using UV detection throughout mainland Mexico will tremendously enhance our knowledge of the scorpion species diversity and geographical distributions there. Indeed, the diversity in many states on the mainland may well approach that of Baja. Table 1. Described and estimated number of infrageneric taxa in the Vaejovidae. Letters denote genera and species groups as follows: A = Paravaejovis; B = Paruroctonus; C = Pseudouroctonus; D = Serradigitus; E = Smeringurus; F = Syntropis; G = Uroctonites; H = Uroctonus; I = Vaejovis eusthenura group; J = V. intrepidus group; K = V. mexicanus group; L = V. nitidulus group; M = V. punctipalpi group; N = unplaced Vaejovis; O = Vejovoidus.
Literature Cited:
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